TRS-80 DOS – TRSDOS v1.3 – SYS11/SYS Disassembled

General:

SYS11/SYS handles the TAPE, PURGE, and LIST library commands.

Disassembly:

ORG 5200H

5200

LD A,55H

Let Register A equal 55H.

5202

LD (42B4H),A

Store the value held in Register A into memory location 42B4H.
NOTE: 42B4H is the storage location for the PROGRAM PROTECT Flag.

5205

XOR A

Set Register A to ZERO and clear all Flags.

5206

LD (4414H),A

Store the value held in Register A into memory location 4414H.
NOTE: 4414H is the storage location for the NUMBER OF THE OVERLAY CURRENTLY IN MEMORY.

5209

LD (42FFH),A

Store the value held in Register A into memory location 42FFH.
NOTE: 42FFH is the storage location for whether a password check is skipped or undertaken in an OPEN command. If Bit 0 is set, the check is skipped.

520C

DEC A

DECrement the value stored in Register A by 1.

520D

LD (427AH),A

Store the value held in Register A into memory location 427AH.
NOTE: 427AH is the storage location for the EXECUTE FILE FLAG.

5210

PUSH HL

Save the COMMAND LINE (pointed to by Register Pair HL) to the top of the stack.

5211

CALL 5226H
[5226H]

Identify the executor which called the Overlay via a GOSUB to 5226H.

5214

JR C,5218H
[5218H]

If the C FLAG (Carry) has been set then that routine wound up with an error, so exit via a JUMP to 5218H.

5216

EX (SP),HL

Put the executor address (held in Register Pair HL) in the memory address representing the top of the stack.

5217

RET

RETurn to the the executor address.

5218H – Exit with a ILLEGAL PARAMETER error.

5218

POP HL

Clear the stack.

5219

LD A,0BH

Let Register A equal 0BH to point to an ILLEGAL PARAMETER error.

521B

JR 5223H
[5223H]

Display the ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

521DH – Exit with a PARAMETER NOT FOUND error.

521D

LD A,0AH

Let Register A equal 0AH to point to a PARAMETER NOT FOUND error.

521F

JR 5223H
[5223H]

Display the PARAMETER NOT FOUND error and exit via a JUMP to 5223H.

5221H – Exit with an error of DISK DRIVE NOT ON.

5221

LD A,02H

Let Register A equal 02H to point to a DISK DRIVE NOT ON error.

5223

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5226H – Decode the COMMAND LINE.

5226

LD HL,523EH

Let Register Pair HL equal 523EH, which is the top of the COMMAND TABLE.

5229

LD A,(HL)

Fetch the first byte on the current row of the COMMAND TABLE and store it into Register A.

522A

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

522B

JR NZ,522FH
[522FH]

If the NZ FLAG (Not Zero) has been set, then we have not run out of table entries, so continue by JUMPing to 522FH.

522D

SCF

We ran out of table entries without a match, so we turn the CARRY FLAG on to indicate an error.

522E

RET

RETurn to the caller.

522FH – Scan the COMMAND TABLE for a match.

522F

CP C

Compare the value held in Register A against the value held in Register C. Results: If Register A equals the value held in Register C, the Z FLAG is set; otherwise the NZ FLAG is set.

5230

JR Z,5237H
[5237H]

If they match, then the Z FLAG (Zero) will have been set, JUMP to 5237H to process the rest of the command.

5232
5233
5234

INC HL
INC HL
INC HL

INCrement the value stored in Register Pair HL by 3 to move to the next line of the COMMAND TABLE.

5235

JR 5229H
[5229H]

Process the next table entry vi a JUMP back to 5229H.

5237H – Determine the JUMP POINT from a MATCHING ENTRY of the COMMAND TABLE.

5237

INC HL

INCrement the value stored in Register Pair HL by 1 to point to the LSB byte of the address of the command.

5238

LD E,(HL)

Fetch the LSB byte of the address of the command (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5239

INC HL

INCrement the value stored in Register Pair HL by 1 to point to the MSB byte of the address of the command.

523A

LD D,(HL)

Fetch the MSB byte of the address of the command (held in the memory location pointed to by Register Pair HL) and store it into Register D.

523B

EX DE,HL

EXchange the value stored in Register Pair HL (the pointer to the COMMAND TABLE) with the value stored in Register Pair DE (the jump address for the matched command).

523C

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

523D

RET

RETurn to the caller.

523EH – COMMAND TABLE.

523E

DEFB 23H

Code for the TAPE command

523F

DEFB A9H 52H

Jump location of 52A9H

5241

DEFB 1EH

Code for the PURGE command

5242

DEFB 0DH 56H

Jump location of 560DH

5244

DEFB 18H

Code for the LIST command

5245

DEFB CCH 58H

Jump location of 58CCH

5247

DEFB 00H

End of Table Delimeter.

5246H – Compare the first “BC” number of bytes of the string at (DE) againg the String at (HL).

5248

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5249

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

524A

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

524B

LD A,(DE)

Fetch a character from the memory location pointed to by Register Pair DE and store it into Register A.

524C

CP (HL)

Compare the fetched character against the character from the memory location pointed to by Register Pair HL.

524D

JR NZ,5254H
[5254H]

If they don’t match then the NZ FLAG (Not Zero) will have been set and we are done, so JUMP to 5254H to restore the registers from the stack with NZ set.

524F

LDI

Move to the 2nd character of both HL and DE via LDI command; which copies BC number of characters from (HL) to (DE), dropping BC each time. When BC hits 0, the PE flag is reset.

5251

JP PE,524BH
[524BH]

If the PARITY/OVERFLOW FLAG has been SET, loop back to 524BH.

5254

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5255

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5256

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

5257

RET

RETurn to the caller.

5258H – Position HL to the next non-space character.

5258

LD A,(HL)

Fetch the value held in the memory location pointed to by Register Pair HL and store it into Register A.

5259

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE) and set the NZ flag if it isn’t a SPACE.

525B

RET NZ

If it isn’t a SPACE then the the NZ FLAG (Not Zero) will have been set, RETurn to the caller.

525C

INC HL

INCrement HL by 1 to point to the next character to check.

525D

JR 5258H
[5258H]

JUMP to 5258H to check that character against a space.

525FH – Pause if “@” is Pressed.

525F

CALL 002BH
[002BH]

GOSUB to 002BH.
NOTE: 002BH is the Model III ROM Keyboard scanning routine; Register A exits with the ASCII value for the key that was pressed or ZERO if no key was pressed.

5262

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5263

RET Z

If no key was pressed then the Z FLAG (Zero) will have been set, RETurn to the caller.

5264

CP 40H

Compare the value held in Register A against 40H (ASCII: @).

5266

RET NZ

If the key pressed was anything other than a @, the NZ FLAG (Not Zero) will have been set, RETurn to the caller.

If we are here, then we got a @ so now we are going to sit and wait for an ENTER.

5267

CALL 0049H
[0049H]

GOSUB to 0049H which is the Model III ROM routine to scan the keyboard and wait until a key is pressed, and then return with the key pressed in Register A. BREAK returns 01H.

526A

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

526C

JR NZ,5267H
[5267H]

If the key we received was not a ENTER then the NZ FLAG (Not Zero) will have been set, so loop back to 5267H.

526E

RET

If we're here, then an ENTER was received, so RETurn to the caller.

526FH - Output a Byte held in Register A to the Screen and, if 5277H is set to 0000H, to the Printer.

526F

CP 09H

Compare the value held in Register A against 09H (ASCII: TAB). Results: If Register A equals TAB, the Z FLAG is set; otherwise the NZ FLAG is set.

5271

JP Z,5A91H
[5A91H]

If a TAB was found, the Z FLAG (Zero) will have been set, so JUMP to 5A91H to process a TAB.

5274

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

5275

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5276

LD BC,(*5277H*)

Let Register Pair BC equal the value placed into memory location 5277H elsewhere in this overlay.

5279
527A

INC C
DEC C

We need to test BC against 0 and, for some reason, the authors decided to do this by INCrementing and then DECrementing the value stored in Register C by 1.

527B

PUSH AF

Save the byte being processed (held in Register Pair AF) to the top of the stack.

527C

CALL NZ,003BH
[003BH]

If the NZ FLAG (Not Zero) has been set, PRINT the character via a GOSUB to 003BH.
NOTE: 003BH is the Model III ROM routine to write the byte held in Register A to the printer, including waiting for the printer to be available OR getting a BREAK. Uses Register Pair DE.

527F

POP AF

Restore the byte being processed (held at the top of the stack) into Register Pair AF.

5280

CALL 0033H
[0033H]

Display the character via a GOSUB to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position.

5283

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

5284

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5285

RET

RETurn to the caller.

5286H - Output a text string pointed to by Register Pair HL to the Screen and, if 5277H is set to 0000H, to the Printer as well.

5286

LD A,(HL)

Fetch a character from the memory location pointed to by Register Pair HL and store it into Register A.

5287

CP 03H

Compare the value held in Register A against 03H, which is one of the standard END OF STRING delimiters.

5289

RET Z

If we are at the end of the string then the Z FLAG (Zero) will have been set, RETurn to the caller.

528A

CALL 526FH
[526FH]

Outputting the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

528D

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN), which is one of the standard END OF STRING delimiters.

528F

RET Z

If we are at the end of the string then the Z FLAG (Zero) will have been set, RETurn to the caller.

5290

INC HL

INCrement the pointer to the current character to deal with (held in Register Pair HL) by 1.

5291

JR 5286H
[5286H]

LOOP back to the top of this routine (i.e., 5286H).

5293H - Output the low nybble of Register A in Hexadecimal to the Screen and, if 5277H is set to 0000H, to the Printer.

5293

AND 0FH

Turn off the high nybble by MASKing the value of Register A against 0FH (0000 1111), turning off bits 7, 6, 5, 4.

The DAA opcode is mysterious, but the first step is to move the value to process into a certain range.

5295

ADD A,90H

LET Register A = Register A + 90H, so that 0-9=90H-99H and A-F=01H-05H.

5297

DAA

Adjust Register A for BCD addition and subtraction operations. DAA is way too complicated to go into here, but if the low 4 bits are greater than 9, the H FLAG is set and 06H is addded to Register A and if the high 4 bits are greater than 9, the C FLAG is set and 60H is added to Register A. The explanation for this is that there are 6 ASCII characters between 9 and A, so adding 6H (for the ones digit) or 60H (for the tens digit), changes A-F into 10-15 in decimal.

The next step in processing a DAA opcode is to adjust the values again.

5298

ADC A,40H

Let Register A = Register A + 40H (plus carry), so that 0-9=30H-39H and A-F=40H-45H)

529A

DAA

529B

JR 526FH
[526FH]

JUMP to 526FH to output the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

529DH - Encode a Two Digit Decimal Number in Text at (HL).

529D

LD (HL),2FH

Initialize the routine by starting (HL), which is the first digit, at one character below "0".

529F

INC (HL)

INCrement the first digit (stored in the memory location pointed to by Register Pair HL) by 1.

52A0

SUB 0AH

Let the first character (held in Register A) = that character - 10.

52A2

JR NC,529FH
[529FH]

As long as that SUB didn't go below 0, the NC flag will be set. In that case, loop back to 529FH and increase the digit held in the memory location pointed to by Register Pair HL by 1 and subtract another 10 from Register A.

52A4

ADD A,3AH

LET Register A = Register A + 3AH to convert the remainder (i.e., the 2nd digit) to ASCII.

52A6

INC HL

INCrement the value stored in Register Pair HL by 1 to point to the second digit.

52A7

LD (HL),A

Store the converted 2nd digit (held in Register A) into the memory location pointed to by Register Pair HL.

52A8

RET

RETurn to the caller.

52A9H - "TAPE" Routine.

52A9

PUSH HL

Save the pointer to the COMMAND LINE (poinetd to by Register Pair HL) to the top of the stack.

The next 5 instructions are a standard way of clearing a memory region. HL is the base, DE = HL + 1, BC = the bytes to move. Then (HL) is set to 00H, which means 00H is then successively copied from one location to the next location, BC number of times.

52AA

LD HL,5BA2H

Let Register Pair HL equal 5BA2H, which will be the base of a buffer 97 characters long to hold a file control block.

52AD

LD DE,5BA3H

Let Register Pair DE equal 5BA3H.

52B0

LD BC,0060H

Let Register Pair BC equal 0060H.

52B3

LD (HL),00H

Store the value held in 00H into the memory location pointed to by Register Pair HL.

52B5

LDIR

Transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

Now 97 bytes of a buffer starting at 5BA2H has been zero'ed.

52B7

POP HL

Restore the pointer to the COMMAND LINE from the stack back into Register Pair HL.

52B8

CALL 5258H
[5258H]

GOSUB to 5258H to position HL to the next non-space character on the COMMAND LINE.

52BB

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

52BD

JP Z,521DH
[521DH]

We hit a CARRIAGE RETURN, which menas we did not get parameters, the Z FLAG (Zero) will have been set and we JUMP to 521DH to exit with an error.

52C0

CP 28H

Compare the value held in Register A against 28H (ASCII: (). Results: If Register A equals (, the Z FLAG is set; otherwise the NZ FLAG is set.

52C2

JP NZ,5219H
[5219H]

If Register A does NOT equal ( then we have a bad COMMAND LINE and the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

52C5

CALL 525CH
[525CH]

GOSUB to 525CH to fetch the next non-space character (pointed to by Register Pair HL) into Register A.

52C8

CP 29H

Compare the value held in Register A against 29H (ASCII: )). Results: If Register A equals ), the Z FLAG is set; otherwise the NZ FLAG is set.

52CA

JP Z,521DH
[521DH]

If we hit a ) which means we have a bad COMMAND LINE, the Z FLAG (Zero) will have been set and we JUMP to 521DH to exit with an error.

52CD

CP 53H

Compare the value held in Register A against 53H (ASCII: S). Results: If Register A equals S, the Z FLAG is set; otherwise the NZ FLAG is set.

52CF

JR NZ,52D9H
[52D9H]

If we didn't get a S (for SOURCE) then the NZ FLAG (Not Zero) will have been set, JUMP to 52D9H to look for the destination spec.

52D1

LD BC,5BA2H

If we're here then we are ready to process the SOURCE filename, so set Register Pair BC to the SOURCE FILE buffer at 5BA2H.

52D4

CALL 531FH
[531FH]

GOSUB to 531FH to get the source device name.

52D7

JR 52CDH
[52CDH]

LOOP BACK 5 instructions to 52CDH to get the next spec.

52D9H - Continuation of "TAPE" Routine. Jumped here to process the command line looking for the Destination spec.

52D9

CP 44H

Compare the value held in Register A against 44H (ASCII: D). Results: If Register A equals D, the Z FLAG is set; otherwise the NZ FLAG is set.

52DB

JR NZ,52E5H
[52E5H]

If we didn't get a D (for DESTINATION) then the NZ FLAG (Not Zero) will have been set, JUMP to 52E5H.

52DD

LD BC,5BD2H

Let Register Pair BC equal 5BD2H to point to the DESTINATION NAME buffer.

52E0

CALL 531FH
[531FH]

GOSUB to 531FH to get the destination device name.

52E3

JR 52CDH
[52CDH]

LOOP back to 52CDH to get the next spec.

52E5H - Continuation of "TAPE" Routine. Jumped here if we didn't get a destination spec.

52E5

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results:

If Register A equals SPACE, the Z FLAG is set.
If A < SPACE, the CARRY FLAG will be set.
if A >= SPACE, the NO CARRY FLAG will be set.

52E7

JR C,52EEH
[52EEH]

If the character was so low in the ASCII range that the C FLAG (Carry) has been set, then we will assume we hit the end of the COMMAND LINE and JUMP to 52EEH.

52E9

CP 29H

Compare the value held in Register A against 29H (ASCII: )). Results: If Register A equals ), the Z FLAG is set; otherwise the NZ FLAG is set.

52EB

JP NZ,5219H
[5219H]

If Register A does NOT equal ) then we have a bad COMMAND LINE and the NZ FLAG (Not Zero) will have been set, so JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

52EE

LD A,(5BA2H)

Fetch a first character in the SOURCE FCB Buffer (held in the buffer starting at 5BA2H) and store it into Register A.

52F1

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

52F2

JP Z,521DH
[521DH]

If there is no character, the Z FLAG (Zero) will have been set, so exit with an error via a JUMP to 521DH.

52F5

LD B,A

Copy the source filename character (held in Register A) into Register B.

52F6

LD A,(5BD2H)

Fetch a character in the destination filename (held in the buffer starting at 5BD2H) and store it into Register A.

52F9

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

52FA

JP Z,521DH
[521DH]

If the Z FLAG (Zero) has been set, JUMP to 521DH, so exit with an error via a JUMP to 521DH.

52FD

CP B

Compare the source filename charcter and the destination filename character (held in Register B. Results): If Register A equals the value held in Register B, the Z FLAG is set; otherwise the NZ FLAG is set.

52FE

JP Z,5219H
[5219H]

If the Z FLAG (Zero) has been set, so JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

5301

PUSH AF

Save the contents of Register Pair AF to the top of the stack.

5302

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5303

CALL 3042H
[3042H]

GOSUB to 3042H, which is a routine in the Model III ROM to set the tape transfer speed.

5306

LD HL,53ADH

Let Register Pair HL equal 53ADH, to point to the message "DEVICE = ".

5309

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

530C

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

530D

POP AF

Put the value held at the top of the STACK into Register Pair AF, and then remove the entry from the stack.

530E

PUSH AF

Save the destination filespec (held in Register A) to the top of the stack.

530F

LD A,B

Copy the source filespec (held in Register B) into Register A.

5310

CP 44H

Compare the value held in Register A against 44H (ASCII: D) to see if the source spec is the DISK.

5312

POP BC

Put the destination spec (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

5313

JP Z,53BCH
[53BCH]

If the Z FLAG (Zero) has been set, then the source spec was a "D"isk, so JUMP to 53BCH.

5316

LD A,B

Copy the destination spec (held in Register B) into Register A.

5317

CP 44H

Compare the value held in Register A against 44H (ASCII: D) to see if the destination spec is "D"ISK.

5319

JP Z,54D3H
[54D3H]

If the destination spec is "D"ISK then the Z FLAG (Zero) will have been set, so JUMP to 54D3H.

531C

JP 55ADH
[55ADH]

Continue the routine via a JUMP to 55ADH.

531FH - Continuation of "TAPE" Routine. Evaluate the Parameter in a Given String.

531F

CALL 525CH
[525CH]

GOSUB to 525CH to fetch the next non-space character (pointed to by Register Pair HL) into Register A.

5322

CP 3DH

Compare the value held in Register A against 3DH (ASCII: =). Results: If Register A equals =, the Z FLAG is set; otherwise the NZ FLAG is set.

5324

JP NZ,5219H
[5219H]

If the character was not an =, then we have a problem and the NZ FLAG (Not Zero) will have been set; so, so JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

5327

CALL 525CH
[525CH]

GOSUB to 525CH to fetch the next non-space character (pointed to by Register Pair HL) into Register A.

532A

LD (BC),A

Store the parameter character (held in Register A) into the memory location pointed to by Register Pair BC.

532B

CP 54H

Compare the value held in Register A against 54H (ASCII: T) to see if TAPE was chosen; Z FLAG will be set it they match.

532D

JR Z,5338H
[5338H]

If the Z FLAG (Zero) has been set, skip the rest of the tests via a JUMP to 5338H.

532F

CP 44H

Compare the value held in Register A against 44H (ASCII: D) to see if DISK was chosen; Z FLAG will be set it they match.

5331

JR Z,5338H
[5338H]

If the Z FLAG (Zero) has been set, skip the rest of the tests via a JUMP to 5338H.

5333

CP 52H

Compare the value held in Register A against 52H (ASCII: R) to see if RAM was chosen; Z FLAG will be set it they match.

5335

JP NZ,5219H
[5219H]

If the NZ FLAG (Not Zero) has been set, JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

5338

CALL 525CH
[525CH]

GOSUB to 525CH to fetch the next non-space character (pointed to by Register Pair HL) into Register A.

533B

CP 2CH

Compare the value held in Register A against 2CH (0010 1100) (ASCII: ,). Results: If Register A equals ,, the Z FLAG is set; otherwise the NZ FLAG is set.

533D

JP Z,525CH
[525CH]

If the Z FLAG (Zero) has been set, JUMP to 525CH to fetch the next non-space character (pointed to by Register Pair HL) into Register A. Since this is a JP rather than a CALL, this will RETurn to the caller.

5340

CP 29H

Compare the value held in Register A against 29H (ASCII: )); if they match the Z FLAG will be set.

5342

RET Z

If the Z FLAG (Zero) has been set then we are done! RETurn to the caller with the Z FLAG set.

5343

CP 20H

Compare the value held in Register A against 20H. If A < 20H, the CARRY FLAG will be set. This is to trap all the usable characters below 20H and we will assume it means we are at the end of line.

5345

RET C

If the C FLAG (Carry) has been set then we have a bad character, so RETurn to the caller with the C FLAG set.

5346

JR 5338H
[5338H]

If we're here then we will continue via a JUMP to 5338H.

5348H - Continuation of "TAPE" Routine. Prompt the user to insert a cassette and wait for a key.

5348

LD HL,5356H

Let Register Pair HL equal 5356H, to point to the message 'Press Any key when Cassette ready' + 0DH.

534B

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

534E

CALL 0049H
[0049H]

Wait for a key press via a GOSUB to the MODEL III ROM Routine at 0049H which is is the Model III ROM routine to scan the keyboard and wait until a key is pressed, and then return with the key pressed in Register A. BREAK returns 01H.

5351

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

5353

JP 0033H
[0033H]

JUMP to 0033H.
NOTE: 0033H is the Model III ROM character print routine; displays the character held in Register A at the current cursor position. Since this was JUMPED to instead of CALLed, the RET at the end of this ROM routine will then RETurn to the caller of this subroutine instead of returning to this place.

5356H - "TAPE" Routine - Message and Byte Storage.

5356

DEFM 'Press Any key when Cassette ready' + 0DH

5378

DEFM 'Disk to Tape - Filespec? ' + 03H

5392

DEFM 'Tape to Disk' + 0DH

539F

DEFM 'Tape into Ram' + 0DH

53AD

DEFM 'Device = ' + 03H

53B7

DEFM '/CMD' + 03H

53CBH - Contination of "TAPE" Routine. Read file from disk into RAM to TAPE save.

53BC

LD HL,5378H

Let Register Pair HL equal 5378H, to point to the message 'Disk to Tape - Filespec? ' + 03H.

53BF

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

53C2

LD HL,5BA2H

Let Register Pair HL equal 5BA2H which is the SOURCE FCB Buffer.

53C5

LD B,18H

Let Register B equal 18H for a loop of 24 characters.

53C7

CALL 0040H
[0040H]

GOSUB to 0040H.
NOTE: 0040H is the Model III ROM routine to get a full line from the keyboard. In this routine, a line is terminated by a carriage return or BREAK, and characters typed are echoed to the display. On entry, B must be the maximum length of line to be accepted and (HL) must be the storage buffer which should be set to B+1. On Exit, CARRY will be set if the BREAK key was hit, Register B will contain the number of characters entered, and (HL) will contain the line from the keyboard followed by the terminating character. Register paid DE is altered in this routine.

53CA

RET C

If the C FLAG (Carry) has been set then a BREAK was pressed; RETurn to the caller.

53CB

LD A,B

Copy the number of the characters received (held in Register B) into Register A.

53CC

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

53CD

RET Z

If NO characters were received then the Z FLAG (Zero) will have been set, RETurn to the caller.

53CE
53CF

LD C,B
LD B,00H

Copy the number of the characters received (held in Register B) into Register Pair BC.

53D1

LD DE,5BD2H

Let Register Pair DE equal 5BD2H to point to the DESTINATION buffer.

53D4

LDIR

53D6

LD A,0DH

Let Register A equal 0DH so that a CARRIAGE RETURN can be put at the end of the filename.

53D8

LD (DE),A

Store the CARRIAGE RETURN held in Register A at the end of the filename (i.e., the memory location pointed to by Register Pair DE).

53D9

LD HL,5D00H

Let Register Pair HL equal 5D00H for a FILE BUFFER.

53DC

LD DE,5BA2H

Let Register Pair DE equal 5BA2H which is the SOURCE FCB Buffer.

53DF

LD B,00H

Let Register B equal 00H so that the next routine will set for FULL SECTOR I/O.

53E1

CALL 4424H
[4424H]

GOSUB to 4424H.
NOTE: 4424H is the SYS00/SYS routine to OPEN A DISK FILE for use. This RST 28H's with a value of 92H so as to call ROUTINE 2 in OVERLAY 3.

53E4

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

53E7

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

53EA

LD DE,5BA2H

Let Register Pair DE equal 5BA2H which is the SOURCE FCB Buffer.

53ED

CALL 0013H
[0013H]

GOSUB to 0013H.
NOTE: 0013H is the Model III ROM routine to read a byte from an input device. Requires DE = starting address of DCB of device and on Exit Register A = byte received from device, Z set if device ready. Uses AF.

53F0

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

53F3

CP 01H

Compare the value held in Register A against 01H, which would be an executable file CODE BLOCK. Results: If Register A equals 01H the Z FLAG is set; otherwise the NZ FLAG is set.

53F5

JR Z,540FH
[540FH]

If the Z FLAG (Zero) has been set, JUMP to 540FH.

53F7

CP 02H

Compare the value held in Register A against 02H, which would be an executable file EXECUTION ADDRESS. Results: If Register A equals 02H the Z FLAG is set; otherwise the NZ FLAG is set.

53F9

JR Z,542CH
[542CH]

If the Z FLAG (Zero) has been set, JUMP to 542CH.

53FB

CP 06H

Compare the value held in Register A against 06H, which would be an executable file COMMENT BLOCK. Results:

If Register A equals 06H.
If A < 06H, the CARRY FLAG will be set.
if A >= 06H, the NO CARRY FLAG will be set.

53FD

JR C,5404H
[5404H]

If the C FLAG (Carry) has been set, JUMP to 5404H.

53FF

LD A,22H

Let Register A equal 22H for a INVALID FILE FORMAT error..

5401

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5404H - Contination of "TAPE" Routine. Routine to handle a COMMENT BLOCK.

5404

CALL 54B3H
[54B3H]

Fetch the COMMENT BLOCK size byte into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

5407

LD B,A

Copy the COMMENT BLOCK size byte (held in Register A) into Register B.

5408

CALL 54B3H
[54B3H]

Get the comment byte into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

540B

DJNZ 5408H
[5408H]

LOOP back to 5408H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

540D

JR 53EAH
[53EAH]

Get the file's next block by JUMPing back to to 53EAH.

540FH - Contination of "TAPE" Routine. Routine to handle a CODE BLOCK.

540F

LD (HL),A

Store BLOCK MARKER (currently held in Register A) into the memory location pointed to by Register Pair HL.

5410

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

5411

CALL 54B3H
[54B3H]

Fetch the CODE BLOCK size byte into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

5414

LD B,A

Copy the CODE BLOCK LENGTH byte (held in Register A) into Register B.

5415

LD (HL),A

Store the CODE BLOCK LENGTH (held in Register A) into the buffer (pointed to by Register Pair HL).

5416

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

5417

CALL 54B3H
[54B3H]

Fetch the LSB of the CODE BLOCK ADDRESS into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

541A

DEC B

DECrement the bytes-left-to-process value stored in Register B by 1.

541B

LD (HL),A

Store the LSB of the CODE BLOCK ADDRESS (held in Register A) into the buffer (pointed to by Register Pair HL).

541C

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

541D

CALL 54B3H
[54B3H]

Fetch the MSB of the CODE BLOCK ADDRESS into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

5420

DEC B

DECrement the bytes-left-to-process value stored in Register B by 1.

5421

LD (HL),A

Store the MSB of the CODE BLOCK ADDRESS (held in Register A) into the buffer (pointed to by Register Pair HL).

5422

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

5423

CALL 54B3H
[54B3H]

Fetch a CODE BYTE into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

5426

LD (HL),A

Store the CODE BYTE (held in Register A) into the buffer (pointed to by Register Pair HL).

5427

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

5428

DJNZ 5423H
[5423H]

Keep processing the entire CODE BLOCK by LOOPing back to 5423H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

542A

JR 53EAH
[53EAH]

Get the file's next block by JUMPing back to to 53EAH.

542CH - Contination of "TAPE" Routine. Routine to handle a EXECUTION ADDRESS BLOCK.

542C

LD (HL),A

Store BLOCK MARKER (currently held in Register A) into the memory location pointed to by Register Pair HL.

542D

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

542E

CALL 54B3H
[54B3H]

Fetch the LENGTH BYTE of the CODE BLOCK ADDRESS into Register A via a GOSUB to 54B3H. This is not going to get preserved.

5431

CALL 54B3H
[54B3H]

Fetch the LSB of the EXECUTION ADDRESS into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

5434

LD (HL),A

Store the LSB of the EXECUTION ADDRESS (held in Register A) into the buffer (pointed to by Register Pair HL).

5435

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

5436

CALL 54B3H
[54B3H]

Fetch the MSB of the EXECUTION ADDRESS into Register A via a GOSUB to 54B3H, which reads a byte from diskettte.

5439

LD (HL),A

Store the MSB of the EXECUTION ADDRESS (held in Register A) into the buffer (pointed to by Register Pair HL).

543AH - Contination of "TAPE" Routine. Passed through from the above routine, this code writes the file from RAM to TAPE.

543A

CALL 5348H
[5348H]

Prompt the user to insert a cassette and wait for a key via a GOSUB to 5348H.

543D

CALL 0287H
[0287H]

Write the TAPE LEADER via a GOSUB to 0287H.

5440

LD A,55H

Let Register A equal 55H to designate the file as a SYSTEM file.

5442

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

5445

LD HL,5BD2H

Let Register Pair HL equal 5BD2H to point to the DESTINATION NAME buffer.

5448

LD B,06H

Since SYSTEM file filenames are 6 characters, set Register B equal 06H.

544A

LD A,(HL)

Fetch a byte from the DESTINATION BUFFER (pointed to by Register Pair HL) and store it into Register A.

544B

CP 2FH

Test the character to see if we have hit the extension by comparing the value held in Register A against 2FH (ASCII: /). Results: If Register A equals /, the Z FLAG is set; otherwise the NZ FLAG is set.

544D

JR Z,545FH
[545FH]

If the Z FLAG (Zero) has been set then we will skip writing the rest of the filename via a JUMP to 545FH.

544F

CP 3AH

Test the character to see if we have hit a drivespec by comparing the value held in Register A against 3AH (ASCII: :). Results: If Register A equals :, the Z FLAG is set; otherwise the NZ FLAG is set.

5451

JR Z,545FH
[545FH]

If the Z FLAG (Zero) has been set then we will skip writing the rest of the filename via a JUMP to 545FH.

5453

CP 30H

Test the character to see it is below the lowest permitted character in a filespec (i.e., "0") by comparing the value held in Register A against 30H (ASCII: 0). Results:

If Register A equals 0, the Z FLAG is set.
If A < 30H 0, the CARRY FLAG will be set.
if A >= 30H 0, the NO CARRY FLAG will be set.

5455

JR C,545FH
[545FH]

If the CARRY FLAG has been set then we will skip writing the rest of the filename via a JUMP to 545FH.

5457

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

545A

INC HL

Move to the next space in the buffer by INCrementing the value stored in Register Pair HL by 1.

545B

DJNZ 544AH
[544AH]

Process up to 6 bytes for a filename by LOOPing back to 544AH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

545D

JR 5466H
[5466H]

If 6 characters found, continue by JUMPing to 5466H.

545FH - Contination of "TAPE" Routine. Jumped to when less than 6 characters of the filename has been written.

First we need to output the remaining characters in the filename as spaces. Register B holds the number of filename characters left to output.

545F

LD A,20H

Let Register A equal 20H which is a SPACE character.

5461

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

5464

DJNZ 545FH
[545FH]

LOOP back to 545FH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5466

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

5469

LD A,(HL)

Fetch a character from the FILE DATA BUFFER (held held in the memory location pointed to by Register Pair HL) and store it into Register A.

546A

CP 02H

Compare the value held in Register A against 02H, which would be an executable file EXECUTION ADDRESS. Results: If Register A equals 02H the Z FLAG is set; otherwise the NZ FLAG is set.

546C

JR Z,54A1H
[54A1H]

If the current character is an EXECUTION ADDRESS BLOCK, then the Z FLAG (Zero) will have been set, JUMP to 54A1H to write the execution address block and exit.

546E

CP 01H

Compare the value held in Register A against 01H, which would be an executable file CODE BLOCK. Results: If Register A equals 01H the Z FLAG is set; otherwise the NZ FLAG is set.

5470

JP NZ,53FFH
[53FFH]

If the current character is NOT a CODE BLOCK ADDRESS, the NZ FLAG (Not Zero) will have been set, JUMP BACK to 53FFH.

5473

INC HL

Point HL to the next byte in the file by INCrementing the value stored in Register Pair HL by 1.

5474

LD A,(HL)

Fetch a character from the FILE DATA BUFFER (held held in the memory location pointed to by Register Pair HL) and store it into Register A.

5475

SUB 02H

Adjust the block by SUBtracting the value 02H from Register A.

5477

LD B,A

Copy the adjusted block length (held in Register A) into Register B.

5478

INC HL

Point HL to the next byte in the file by INCrementing the value stored in Register Pair HL by 1.

5479

CALL 547EH
[547EH]

Write the entire block via a GOSUB to 547EH.

547C

JR 5469H
[5469H]

LOOP BACK to 5469H to keep processing data blocks.

547EH - Subroutine in the "TAPE" Routine - Write an entire code block to tape, with checksum. Register B holds the data block length and Register C will calculate the checksum.

547E

LD A,3CH

Prepare to write the DATA BLOCK IDENTIFIER by setting Register A to 3CH.

5480

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

5483

LD A,B

Copy the DATA BLOCK LENGTH from Register B into Register A.

5484

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

5487

LD A,(HL)

Fetch a data byte (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5488

LD C,A

Initialize the checksum counter by copying the contents of Register A into Register C.

5489

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

548C

INC HL

Point HL to the next byte in the data block by INCrementing the value stored in Register Pair HL by 1.

548D

LD A,(HL)

Fetch a data byte (held in the memory location pointed to by Register Pair HL) and store it into Register A.

548E

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

5491

ADD A,C

Update the checksum by setting Register A = Register A + Register C.

5492

LD C,A

Copy the updated checksum (held in Register A) into Register C.

5493

INC HL

Point HL to the next byte in the data block by INCrementing the value stored in Register Pair HL by 1.

5494

LD A,(HL)

Fetch a data byte (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5495

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

5498

ADD A,C

Update the checksum by setting Register A = Register A + Register C.

5499

LD C,A

Copy the updated checksum (held in Register A) into Register C.

549A

DJNZ 5493H
[5493H]

LOOP back to 5493H for the entire data block length, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

549C

INC HL

Point HL to the next byte in the data block by INCrementing the value stored in Register Pair HL by 1.

549D

LD A,C

Copy the checksum (held in Register C) into Register A.

549E

JP 0264H
[0264H]

JUMP to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate. Since this is a JUMP instead of a GOSUB, the RET inside that JUMP will return to the caller.

54A1H - Contination of "TAPE" Routine. Jumped to when we have an EXECUTION ADDRESS BLOCK. This routine will write the block and then exit the routine.

54A1

INC HL

Point HL to the next byte in the data block by INCrementing the value stored in Register Pair HL by 1.

54A2

LD A,78H

Prepare to write the EXECUTION ADDRESS IDENTIFIER by setting Register A to 78H.

54A4

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

54A7

LD A,(HL)

Fetch a data byte (held in the memory location pointed to by Register Pair HL) and store it into Register A. This will be the LSB of the execution address.

54A8

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

54AB

INC HL

Point HL to the next byte in the data block by INCrementing the value stored in Register Pair HL by 1.

54AC

LD A,(HL)

Fetch a data byte (held in the memory location pointed to by Register Pair HL) and store it into Register A. This will be the MSB of the execution address.

54AD

CALL 0264H
[0264H]

GOSUB to 0264H which is the Model III ROM routine to output a byte held in Register A to cassette. This routine must be called often enough to keep up with the baud rate.

54B0

JP 01F8H
[01F8H]

JUMP to the Model III ROM Routine at 01F8H to turn off the cassette motor. Since this is a JUMP instead of a GOSUB, the RET inside that JUMP will return to the caller.

54B3H - Subroutine in the "TAPE" Routine. Read a Byte from the Disk File.

54B3

LD DE,5BA2H

Let Register Pair DE equal 5BA2H which is the SOURCE FCB Buffer.

54B6

CALL 0013H
[0013H]

54B9

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

54BC

RET

RETurn to the caller.

54BDH - Subroutine in the "TAPE" Routine. Write a Byte to the Disk File.

54BD

PUSH AF

Save the contents of Register Pair AF to the top of the stack.

54BE

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

54BF

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

54C0

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

54C1

PUSH IY

Save the contents of Special Index Register IY to the top of the stack.

54C3

LD DE,5BA2H

Let Register Pair DE equal 5BA2H which is the SOURCE FCB Buffer.

54C6

CALL 001BH
[001BH]

GOSUB to 001BH.
NOTE: 001BH is the Model III ROM routine to write a byte to an output device. Requires Register A to contain the byte to output and Register Pair DE to be the starting address of DCB of device. On exit, Z set if device ready. Uses AF.

54C9

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

54CC

POP IY

Put the value held at the top of the STACK into Special Index Register IY, and then remove the entry from the stack.

54CE

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

54CF

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

54D0

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

54D1

POP AF

Put the value held at the top of the STACK into Register Pair AF, and then remove the entry from the stack.

54D2

RET

RETurn to the caller.

54D3H - Part of "TAPE" Routine. Transfer a File from Tape to RAM for Disk Save.

54D3

LD HL,5392H

Let Register Pair HL equal 5392H, which points to the message "TAPE TO DISK".

54D6

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

54D9

CALL 5348H
[5348H]

Prompt the user to insert a cassette and wait for a key via a GOSUB to 5348H.

54DC

CALL 0243H
[0243H]

GOSUB to 0243H which is the Model III ROM Routine to start the tape and read the header.

54DF

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

54E2

CP 55H

Compare the byte which was just read from cassette (held in Register A) against 55H, which is the SYSTEM TAPE identifier. Results: If Register A equals 55H, the Z FLAG is set; otherwise the NZ FLAG is set.

54E4

JP NZ,5219H
[5219H]

If the byte read was not a SYSTEM TAPE identifier, then we have a problem; JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

54E7

LD HL,(4020H)

Fetch the value held in memory location 4020H and store it into Register Pair HL.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

54EA

LD IY,5BA2H

Let Special Index Register IY equal 5BA2H which is the SOURCE FCB Buffer.

54EE

LD B,06H

Since a maching language file's filename is 6 characters, set Register B equal 06H.

54F0

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

54F3

LD (HL),A

Store byte which was just read from cassette (held in Register A) into the screen location pointed to by Register Pair HL.

54F4

INC HL

INCrement the screen location (stored in Register Pair HL) by 1.

54F5

CP 21H

Compare the value held in Register A against 21H (ASCII: SPACE + 1). If Register A < SPACE + 1, the CARRY FLAG will be set.

54F7

JR C,54FEH
[54FEH]

If the byte is a SPACE or lower, then we are at the end of the filename and the C FLAG (Carry) will have been set, JUMP to 54FEH.

54F9

LD (IY+00H),A

Store the byte read from tape (which is part of the filename) into the filename buffer pointed to by Special Index Register IY+00H.

54FC

INC IY

INCrement Special Index Register IY by 1 to point to the next available spot in the filename buffer.

54FE

DJNZ 54F0H
[54F0H]

LOOP back to 54F0H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5500

LD (4020H),HL

Store the value held in Register Pair HL into memory location 4020H.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

5503

PUSH IY
POP DE

Let Register Pair DE = Special Register Index IY. At this point DE will the 1 byte beyond the filename.

5506

LD HL,53B7H

Let Register Pair HL equal 53B7H to point to the message "/CMD + 03H".

5509

LD BC,0005H

We have 5 bytes to move so set Register Pair BC equal 0005H.

550C

LDIR

Add the "/CMD + 03H" to the end of the filename by transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

550E

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

Top of a loop (ending at 5544H) to read the entire file from tape.

5511

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

5514

CP 78H

Check to see if the byte is an EXECUTION ADDRESS IDENTIFIER by comparing the value held in Register A against 78H. Results: If Register A equals 78H, the Z FLAG is set; otherwise the NZ FLAG is set.

5516

JR Z,5546H
[5546H]

If we are at an EXECUTION ADDRESS IDENTIFIER BYTE, the Z FLAG (Zero) will have been set, so JUMP to 5546H.

5518

CP 3CH

Check to see if the byte is a CODE BLOCK IDENTIFIER by comparing the value held in Register A against 3CH. Results: If Register A equals 3CH, the Z FLAG is set; otherwise the NZ FLAG is set.

551A

JR NZ,5511H
[5511H]

If the byte read was NOT a CODE BLOCK IDENTIFIER then loop back to 5511H and keep reading.

If we are here, then the byte read from the cassette was a CODE BLOCK identifier.

551C

LD (HL),01H

Store a CODE BLOCK MARKER (01H) into the FILE BUFFER (pointed to by Register Pair HL).

551E

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

Next, process the BLOCK LENGTH.

551F

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

5522

LD B,A

5523

ADD A,02H

Adjust the BLOCK LENGTH by 2 to deal with diskette, by setting Register A = Register A + 02H.

5525

LD (HL),A

Store the adjusted BLOCK LENGTH into the FILE BUFFER (pointed to by Register Pair HL).

5526

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

Next, process the LSB of the CODE ADDRESS.

5527

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

552A

LD C,A

Prepare to calculate the file's checksum by copying the contents of Register A (i.e., the LSB of the CODE ADDRESS) into Register C.

552B

LD (HL),A

Store the value held in Register A (which is the LSB of the CODE ADDRESS) into the memory location pointed to by Register Pair HL.

552C

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

Next, process the MSB of the CODE ADDRESS.

552D

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

5530

LD (HL),A

Store the value held in Register A (which is the MSB of the CODE ADDRESS) into the memory location pointed to by Register Pair HL.

5531

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

5532

ADD A,C

LET Register A = Register A + Register C.

5533

LD C,A

Copy the contents of Register A (i.e., the checksum which now includes the MSB of the CODE ADDRESS) into Register C.

Next, loop to read the block

5534

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

5537

LD (HL),A

Store the value held in Register A (i.e., a data byte) into the FILE BUFFER at the location pointed to by Register Pair HL.

5538

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

5539

ADD A,C

LET Register A = Register A + Register C.

553A

LD C,A

Copy the contents of Register A (i.e., the checksum which now includes the most recently read data byte) into Register C.

553B

DJNZ 5534H
[5534H]

LOOP back to 5534H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

The block is now read into the buffer at HL, and Register C now holds the checksum. So next, verify the checksum.

553D

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

5540

CP C

Compare the the checksum as read from the tape (held in Register A) against the checksum as just calculated (held in Register C). Results: If the checksums match, the the Z FLAG is set; otherwise the NZ FLAG is set.

5541

JP NZ,5219H
[5219H]

If the NZ FLAG (Not Zero) has been set, JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

5544

JR 5511H
[5511H]

JUMP to 5511H.

5546H - Contination of "TAPE" Routine. Jumped to when we have an EXECUTION ADDRESS to write that block and finish.

5546

LD (HL),02H

Store an EXECUTE ADDRESS MARKER (02H) into the FILE BUFFER at the location pointed to by Register Pair HL.

5548

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

5549

LD (HL),02H

Store the length of a EXECUTE ADDRESS, which is ALWAYS 2 bytes, into the FILE BUFFER at the location pointed to by Register Pair HL.

554B

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

554C

PUSH HL

Save the current location in the FILE BUFFER (held in Register Pair HL) to the top of the stack.

554D

CALL 0314H
[0314H]

Read the execution address from the tape via a GOSUB to 0314H which reads 2 bytes from the cassette and puts them into HL and 40DFH and then turns off the cassette motor.

5550

POP DE

Restore the current location in the FILE BUFFER (held at the top of the stack) into Register Pair DE.

5551

EX DE,HL

EXchange the value stored in Register Pair HL (i.e., the execution address from the CALL 0314H) with the value stored in Register Pair DE (i.e., the current location in the FILE BUFFER).

5552
5552

LD A,D
OR E

Since the Z-80 cannot test Register Pair DE against zero, the common trick is to set Register A to equal to Register D, and then OR A against Register E. Only if both Register D and Register E were zero can the Z FLAG be set.

5554

JR NZ,5559H
[5559H]

If that OR showed that DE was NOT empty, then we have an execution address then the NZ FLAG (Not Zero) will have been set, so skip the next instruction which (sets a default) and JUMP to 5559H.

5556

LD DE,402DH

Since DE was empty, set a default EXECUTION ADDRESS at 402DH, which is the address to transfer to DOS.

5559

LD (HL),E

Store the LSB of the EXECUTION ADDRESS (held in Register E) into the memory location pointed to by Register Pair HL.

555A

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

555B

LD (HL),D

Store the MSB of the EXECUTION ADDRESS (held in Register D) into the memory location pointed to by Register Pair HL.

555C

CALL 01F8H
[01F8H]

Turn off the cassette player via a GOSUB to 01F8H.

555FH - Contination of "TAPE" Routine. Write a File from RAM to Diskette.

555F

LD HL,5D00H

Let Register Pair HL equal 5D00H for a FILE BUFFER.

5562

LD DE,5BA2H

Let Register Pair DE equal 5BA2H for a SOURCE FCB Buffer.

5565

LD B,00H

Let Register B equal 00H so that the next routine will set for FULL SECTOR I/O.

5567

CALL 4420H
[4420H]

GOSUB to 4420H.
NOTE: 4420H is the SYS00/SYS routine to INITIALIZE A FILE (i.e., CREATE or OPEN). This RST 28H's with a value of A2H so as to call ROUTINE 2 in OVERLAY 2. Register HL needs to point to a RAM BUFFER for the DCB's.

556A

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

556D

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

5570

LD A,(HL)

Fetch a byte from the FILE BUFFER (the memory location pointed to by Register Pair HL) and store it into Register A.

5571

CP 02H

Compare the value held in Register A against 02H, which would be an executable file EXECUTION ADDRESS BLOCK indicator. Results: If Register A equals 02H the Z FLAG is set; otherwise the NZ FLAG is set.

5573

JR Z,5599H
[5599H]

If the Z FLAG (Zero) has been set, JUMP to 5599H to deal with an EXECUTION ADDRESS BLOCK.

5575

CP 01H

Compare the value held in Register A against 01H, which would be an executable file CODE BLOCK. Results: If Register A equals 01H the Z FLAG is set; otherwise the NZ FLAG is set.

5577

JP NZ,5219H
[5219H]

If the NZ FLAG (Not Zero) has been set, JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

557A

CALL 54BDH
[54BDH]

Write the byte held in Register A to the disk file via a GOSUB to 54BDH.

557D

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

557E

LD A,(HL)

Fetch the CODE BLOCK LENGTH (the next byte from the FILE BUFFER) and store it into Register A.

557F

LD B,A

Copy the contents of Register A into Register B, because B is the DJNZ LOOP counter.

5580

CALL 54BDH
[54BDH]

Write the CODE BLOCK LENGTH (i.e., the byte held in Register A) to the disk file via a GOSUB to 54BDH.

5583

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1 to point to the LSB of the Execution Address.

5584

LD A,(HL)

Fetch the the LSB of the Execution Address (the next byte in the FILE BUFFER) and store it into Register A.

5585

CALL 54BDH
[54BDH]

Write the LSB of the Execution Address (the byte held in Register A) to the disk file via a GOSUB to 54BDH.

5588

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1 to point to the MSB of the Execution Address.

5589

LD A,(HL)

Fetch the the MSB of the Execution Address (the next byte in the FILE BUFFER) and store it into Register A.

558A

CALL 54BDH
[54BDH]

Write the MSB of the Execution Address (the byte held in Register A) to the disk file via a GOSUB to 54BDH.

558D
558E

DEC B
DEC B

DECrement the BLOCK LENGTH (stored in Register B) by 2.

558F

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

5590

LD A,(HL)

Fetch a byte from the FILE BUFFER (the memory location pointed to by Register Pair HL) and store it into Register A.

5591

CALL 54BDH
[54BDH]

Write the byte held in Register A to the disk file via a GOSUB to 54BDH.

5594

DJNZ 558FH
[558FH]

LOOP back to 558FH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5596

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

5597

JR 5570H
[5570H]

Process the next block by JUMPing BACK to 5570H.

5599H - Contination of Write a File from RAM to Diskette portion of the "TAPE" Routine. Jumped here if an EXECUTE ADDRESS BLOCK was found.

5599

CALL 54BDH
[54BDH]

Write the EXECUTE ADDRESS MARKER (which is 02H) held in Register A to the disk file via a GOSUB to 54BDH.

559C

CALL 54BDH
[54BDH]

Write the BLOCK LENGTH BYTE (which is always 02H) held in Register A to the disk file via a GOSUB to 54BDH.

559F

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1. Note: This byte gets thrown away.

55A0

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

55A1

LD A,(HL)

Fetch the LSB of the EXECUTE ADDRESS (held in the memory location pointed to by Register Pair HL) and store it into Register A.

55A2

CALL 54BDH
[54BDH]

Write the LSB of the EXECUTE ADDRESS held in Register A to the disk file via a GOSUB to 54BDH.

55A5

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

55A6

LD A,(HL)

Fetch the MSB of the EXECUTE ADDRESS (held in the memory location pointed to by Register Pair HL) and store it into Register A.

55A7

CALL 54BDH
[54BDH]

Write the MSB of the EXECUTE ADDRESS held in Register A to the disk file via a GOSUB to 54BDH.

55AA

JP 4428H
[4428H]

JUMP to 4428H.
NOTE: 4428H is the SYS00/SYS routine to CLOSE A DISK FILE. This RST 28H's with a value of 93H so as to call ROUTINE 1 in OVERLAY 3.

55ADH - Continuation of the "TAPE" Routine. Load a SYSTEM Tape into RAM and RUN IT.

55AD

LD HL,539FH

Let Register Pair HL equal 539FH, to point to the message "TAPE INTO RAM".

55B0

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

55B3

CALL 5348H
[5348H]

Prompt the user to insert a cassette and wait for a key via a GOSUB to 5348H.

55B6

CALL 0243H
[0243H]

Turn on the CASSETTE TAPE and READ THE FILE HEADER via a GOSUB to 0243H.

55B9

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

55BC

CP 55H

55BE

JP NZ,5219H
[5219H]

If the byte read was not a SYSTEM TAPE identifier, then we have a problem; JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

55C1

LD HL,(4020H)

Fetch the value held in memory location 4020H and store it into Register Pair HL.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

55C4

LD B,06H

Since a maching language file's filename is 6 characters, set Register B equal 06H.

55C6H

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

55C9

LD (HL),A

Store byte which was just read from cassette (held in Register A) into the screen location pointed to by Register Pair HL.

55CA

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

55CB

DJNZ 55C6H
[55C6H]

LOOP back to 55C6H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

55CD

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A. This will be a BLOCK MARKER.

55D0

CP 78H

Check to see if the BLOCK MARKER just read was an EXECUTION ADDRESS BLOCK by comparing the value held in Register A against 78H. Results: If Register A equals 78H, the Z FLAG is set; otherwise the NZ FLAG is set.

55D2

JR Z,5601H
[5601H]

If the byte was an EXECUTION ADDRESS BLOCK then the Z FLAG (Zero) will have been set, JUMP to 5601H.

55D4

CP 3CH

>Check to see if the BLOCK MARKER just read was a CODE BLOCK by comparing the value held in Register A against 3CH. Results: If Register A equals 3CH, the Z FLAG is set; otherwise the NZ FLAG is set.

55D6

JR NZ,55CDH
[55CDH]

If the byte was NOT a CODE BLOCK then the NZ FLAG (Zero) will have been set; LOOP BACK to 55CDH to keep reading bytes.

55D8

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A. This should be the CODE BLOCK LENGTH BYTE.

55DB

LD B,A

Copy the CODE BLOCK LENGTH BYTE (held in Register A) into Register B.

55DC

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A. This should be the LSB of the CODE ADDRESS.

55DF

LD C,A

Copy the LSB of the CODE ADDRESS (held in Register A) into Register C.

55E0

LD L,A

Copy the LSB of the CODE ADDRESS (held in Register A) into Register L.

55E1

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A. This should be the MSB of the CODE ADDRESS.

55E4

LD H,A

Copy the MSB of the CODE ADDRESS (held in Register A) into Register H.

55E5

ADD A,C

LET Register A = the MSB of the CODE ADDRESS (held in Register A) + the LSB of the CODE ADDRESS (held in Register C).

55E6

LD C,A

Copy the results of that addition into Register C.

55E7

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A.

55EA

LD (HL),A

Store the byte just read from tape (held in Register A) into the FILE BUFFER location pointed to by Register Pair HL.

55EB

CP (HL)

Verify that the byte was properly written by comparing the value held in Register A against the value held in the memory location pointed to by the value held in Register Pair HL. Results: If they match, the Z FLAG is set; otherwise the NZ FLAG is set.

55EC

JR Z,55F3H
[55F3H]

If the write was verified successfully the Z FLAG (Zero) will have been set, JUMP to 55F3H.

55EE

LD A,23H

Let Register A equal 23H for a DOS ERROR of MEMORY FAULT.

55F0

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

55F3H - Continuation of the SYSTEM Tape into RAM and RUN IT portion of the "TAPE" Routine. Jumped here if there was no memory fault.

55F3

ADD A,C

LET Register A = Register A + the checksum (held in Register C).

55F4

LD C,A

Copy the checksum (held in Register A) into Register C.

55F5

INC HL

INCrement the FILE BUFFER POINTER (stored in Register Pair HL) by 1.

55F6

DJNZ 55E7H
[55E7H]

Process the entire code block (length of B) by LOOPing back to 55E7H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

55F8

CALL 0235H
[0235H]

GOSUB to 0235H which is the Model III ROM Routine to read one byte from the cassette drive specified in register A, and returns the byte in register A. This should be the CODE BLOCK's CHECKSUM

55FB

CP C

Compare the CODE BLOCK's CHECKSUM which was just calculated (held in Register C) against rhe CODE BLOCK's CHECKSUM read from cassette (held in Register A): If they match, the Z FLAG is set; otherwise the NZ FLAG is set.

55FC

JP NZ,5219H
[5219H]

If they don't match, then we had a bad read and the NZ FLAG (Not Zero) will have been set, JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

55FF

JR 55CDH
[55CDH]

If they did match, then LOOP BACK to 55CDH to read the next block.

5601H - Continuation of the SYSTEM Tape into RAM and RUN IT portion of the "TAPE" Routine. Jumped here if the we just got a EXECUTION ADDRESS BLOCK.

5601

CALL 0314H
[0314H]

Read the EXECUTION ADDRESS via a GOSUB to the Model III ROM Routine at 0314H.

5604

PUSH HL

Save the EXECUTION ADDRESS (held in Register Pair HL from that CALL) to the top of the stack.

5605

CALL 01F8H
[01F8H]

Turn off the cassette via a call to the MODEL III ROM Routine at 01F8H.

5608

POP HL

Restore the EXECUTION ADDRESS (held at the top of the stack) into Register Pair HL, and then remove the entry from the stack.

5609
5609

LD A,H
OR L

We want to see if HL is 0. However, the Z-80 cannot test Register Pair HL against zero. The common trick is to set Register A to equal to Register H, and then OR A against Register L. Only if both Register H and Register L were zero can the Z FLAG be set.

560B

RET Z

If we didn't get an execution address then the Z FLAG (Zero) will have been set, RETurn to the caller.

560C

JP (HL)

If we are here then we have an execution address stored in Register Pair HL. So JUMP to it!.

560DH - "PURGE" Library Command.

560D

CALL 5258H
[5258H]

GOSUB to 5258H to position HL to the next non-space character on the COMMAND LINE.

5610

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5612

JR Z,5647H
[5647H]

If all we got was a CARRIAGE RETURN, then we will assume that this is a request to delete user files from Drive 0; so JUMP to 5647H.

5614

CP 2AH

Compare the value held in Register A against 2AH (ASCII: *). Results: If Register A equals *, the Z FLAG is set; otherwise the NZ FLAG is set.

5616

JR NZ,561DH
[561DH]

If we didn't get a * (for DELETE DOS), JUMP to 561DH.

If we are here, then we got a * and need to delete DOS.

5618

LD (58C5H),A

Store a * unto the CP instruction at 58C5H.

561B

INC HL

BUMP the pointer to the COMMAND LINE by 1.

561C

LD A,(HL)

Fetch the next character on the COMMAND LINE from the memory location pointed to by Register Pair HL and store it into Register A.

561D

CP 3AH

Compare the value held in Register A against 3AH (ASCII: :) to see if we were given a drivespec. Results: If Register A equals :, the Z FLAG is set; otherwise the NZ FLAG is set.

561F

JR NZ,563AH
[563AH]

If we were not given a :, then skip the drivespec checking and JUMP to 563AH.

If we are here, then we got a : and need to check for a drive letter after the :

5621

INC HL

BUMP the pointer to the COMMAND LINE by 1.

5622

LD A,(HL)

Fetch the next character on the COMMAND LINE from the memory location pointed to by Register Pair HL and store it into Register A. A drive number is expected to be here.

5623

LD (58C7H),A

Store the drive spec held in Register A (which should be a drive number) into memory location 58C7H.

5626

SUB 30H

SUBtract the value 30H from Register A. Note: Subtracting 30H from from Register A will convert an ASCII number '0'-'9' to its decimal equivalent (i.e., 6 in ASCII is 36H in Hex; so 36H-30H = 6).

5628

JP C,5221H
[5221H]

If value on the command line was below "0" the C FLAG (Carry) will have been triggered; JUMP to 5221H.

562B

LD B,A

Copy the ASCII value of the drive number (held in Register A) into Register B.

562C

LD A,(4413H)

Fetch the value held in memory location 4413H and store it into Register A.
NOTE: 4413H is the storage location for the NUMBER OF DISK DRIVES in the system.

562F

CP B

Compare the NUMBER OF DISK DRIVES in the system (held in Register A) against the ASCII value of the user supplied drive number (held in Register B). If A < B then we have a BAD drive number, and the CARRY FLAG will be set.

5630

JP C,5221H
[5221H]

If the user supplied a bad drive number, JUMP to 5221H.

5633

LD A,B

Copy the ASCII value of the drive number (held in Register B) into Register A.

5634

LD (58C9H),A

Store the drive number (in ASCII) into memory location 58C9H.

5637

CALL 525CH
[525CH]

GOSUB to 525CH to fetch the next non-space character (pointed to by Register Pair HL) into Register A.

563A

CP 28H

Compare the value held in Register A against 28H (ASCII: (). Results: If Register A equals (, the Z FLAG is set; otherwise the NZ FLAG is set.

563C

JR NZ,5647H
[5647H]

If the next character on the command line was not "(" then the NZ FLAG (Not Zero) will have been set; JUMP to 5647H.

563E

LD DE,58A6H

Let Register Pair DE equal 58A6H to point to the PURGE command parameter table.

5641

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

5644

JP NZ,521DH
[521DH]

If the CALL resulted in an error the NZ FLAG (Not Zero) will have been set, JUMP to 521DH.

5647

LD HL,5866H

Let Register Pair HL equal 5866H to point to the message "MASTER PASSWORD?" .

564A

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

564D

LD HL,5BA2H

Let Register Pair HL equal 5BA2H which will be a buffer for the MASTER PASSWORD.

5650

LD B,08H

Since a password is 8 characters or less, set Register B equal 08H.

5652

CALL 0040H
[0040H]

5655

PUSH HL

Save the MASTER PASSWORD BUFFER ADDRESS (held in Register Pair HL) to the top of the stack.

5656

LD B,08H

Since a password is 8 characters or less, set Register B equal 08H.

5658

LD A,(HL)

We are in a loop here. Fetch a character from the MASTER PASSWORD BUFFER (i.e., held in the memory location pointed to by Register Pair HL) and store it into Register A.

5659

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results:

If Register A equals SPACE, the Z FLAG is set.
If A < SPACE, the CARRY FLAG will be set.
if A >= SPACE, the NO CARRY FLAG will be set.

565B

JR C,5662H
[5662H]

If the character from the MASTER PASSWORD BUFFER (held in Register A) < SPACE, we are at the end of the password and the C FLAG (Carry) will have been set; so JUMP to 5662H to stop processing characters.

565D

INC HL

BUMP HL by 1 to point to the next character in the MASTER PASSWORD BUFFER.

565E

DJNZ 5658H
[5658H]

LOOP back to 5658H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5660

JR 5667H
[5667H]

If we are here, then 8 characters were processed for the Master Password. Continue via a JUMP to 5667H.

5662H - Continuation of "PURGE". Jumped here if the MASTER PASSWORD provided by the user was less than 8 characters. Register B will hold the number of characters received and Register Pair HL will be pointing to the first non-valid character in the Master Password Buffer.

5662

LD (HL),20H

Overwrite whatever may be in the MASTER PASSWORD CHARACTER BUFFER at HL with a SPACE.

5664

INC HL

BUMP HL by 1 to point to the next character in the MASTER PASSWORD BUFFER.

5665

DJNZ 5662H
[5662H]

LOOP back to 5662H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5667

POP DE

Put the MASTER PASSWORD BUFFER ADDRESS (held at the top of the STACK into Register Pair DE), and then remove the entry from the stack.

5668

CALL 57A4H
[57A4H]

Encode the password pointed to by Register Pair DE into Register Pair HL via GOSUB to 57A4H.

566B

LD (58CAH),HL

Store hashed master password (held in Register Pair HL into) memory location 58CAH.

566E

LD A,(58C9H)

Fetch the drive number from memory location 58C9H and store it into Register A.

5671

LD C,A

Since SYS00/SYS Disk I/O calls usually require Register C to contain the drive number, copy the drive number (held in Register A) into Register C.

5672

CALL 4A93H
[4A93H]

GOSUB to 4A93H.
NOTE: 4A93H is the SYS00/SYS routine to READ THE GAT sector into RAM (Buffer at 4D00H).

5675

JP NZ,4409H
[4409H]

If that CALL resulted in an error the NZ FLAG (Not Zero) will have been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5678

CALL 4ABAH
[4ABAH]

GOSUB to 4ABAH.
NOTE: 4ABAH is the SYS00/SYS routine to read the HIT sector into RAM.

567B

JP NZ,4409H
[4409H]

If that CALL resulted in an error the NZ FLAG (Not Zero) will have been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

567E

LD HL,4300H

Let Register Pair HL equal 4300H.
NOTE: 4300H is a memory buffer (referred to as Memory Buffer 1) where HIT TABLE was stored in RAM.

5681

LD DE,5D00H

Let Register Pair DE equal 5D00H, which will be a memory buffer for the HIT SAVE AREA.

5684

LD BC,0100H

Let Register Pair BC equal 0100H, which is a full disk sector of data.

5687

LDIR

Copy 256 bytes from 4300H to 5D00H via a LDIR which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

5689

LD HL,(4DCEH)

Fetch the actual hashed master password from the HIT (held in memory location 4DCEH) and store it into Register Pair HL.

568C

LD DE,(58CAH)

Fetch the user provided hashed master password (held in memory location 58CAH) and store it into Register Pair DE.

5690

OR A

Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5691

SBC HL,DE

Compare the actual password (HL) with the user provided password (DE) by subtracting them.

5693

JR Z,569AH
[569AH]

If the two password match, the subtraction will be 0 and the Z FLAG (Zero) will have been set; JUMP to 569AH.

5695

LD A,19H

Let Register A equal 19H to set up for a FILE ACCESS DENIED error.

5697

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

569AH - Continuation of "PURGE". Jumped here if the MASTER PASSWORD provided by the user was correct.

569A

LD A,(58C5H)

Check to see if the user requested to delete all of DOS by fetching the value held in memory location 58C5H and store it into Register A.

569D

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

569E

CALL NZ,57D4H
[57D4H]

If the NZ FLAG (Not Zero) has been set, then the user wants to delete DOS so GOSUB to 57D4H.

56A1

LD HL, ~~ the value placed into 56A2 ~~

Let Register Pair HL equal a value placed here from other locations in this Overlay. The hope here is that HL points to the HASH TABLE ENTRY for the file to be deleted.

56A4

LD A,L

Isolate the position in the HIT into Register A by copying the contents of Register L into Register A.

56A5

CP 51H

Check to see if we are at the end of the HIT by comparing the value held in Register A against 51H. Results: If Register A equals 51H, the Z FLAG is set; otherwise the NZ FLAG is set.

56A7

JP Z,5791H
[5791H]

If Register A = 51H then we are past the end of the HIT and the Z FLAG (Zero) will have been set; JUMP to 5791H to finish.

56AA

LD A,(HL)

Fetch the HIT entry (held in the memory location pointed to by Register Pair HL) and store it into Register A.

56AB

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

56AC

JR NZ,56B4H
[56B4H]

If the HIT entry is NOT ZERO, then there is a file there to be processed, so JUMP to 56B4H.

56AE

INC HL

Point to the next entry in the HIT TABLE by INCrementing the value stored in Register Pair HL by 1.

56AF

LD (56A2H),HL

Store the HIT TABLE pointer (which was just incremented) into the LD HL,nnnn instruction at 56A1 and then ...

56B2

JR 56A1H
[56A1H]

... JUMP to 56A1H.

56B4H - Continuation of "PURGE". Jumped here if HL points to a HIT entry that needs to be deleted.

56B4

LD B,L

Copy the Logical File Number (held in Register L) into Register B.

56B5

LD A,(58C9H)

Fetch the drive number from memory location 58C9H and store it into Register A.

56B8

LD C,A

Since SYS00/SYS Disk I/O calls usually require Register C to contain the drive number, copy the drive number (held in Register A) into Register C.

56B9

CALL 4A67H
[4A67H]

GOSUB to 4A67H.
NOTE: 4A67H is the SYS00/SYS routine to read the directory entry into RAM (Buffer at 4300H)

56BC

JP NZ,4409H
[4409H]

If that CALL resulted in an error, the NZ FLAG (Not Zero) will have been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

56BF

LD A,(HL)

Fetch the file attributes (held in the memory location pointed to by Register Pair HL) and store it into Register A.

56C0

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

56C1

JR NZ,56E3H
[56E3H]

If the NZ FLAG (Not Zero) has been set then the file is active, so skip the next routine and JUMP to 56E3H.

56C3

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

56C4

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

56C5

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

56C6

PUSH AF

Save the contents of Register Pair AF to the top of the stack.

56C7

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

56C8

LD A,(58C9H)

Fetch the drive number from memory location 58C9H and store it into Register A.

56CB

LD C,A

Since SYS00/SYS Disk I/O calls usually require Register C to contain the drive number, copy the drive number (held in Register A) into Register C.

56CC

CALL 4ABAH
[4ABAH]

GOSUB to 4ABAH.
NOTE: 4ABAH is the SYS00/SYS routine to read the HIT sector into RAM.

56CF

JP NZ,4409H
[4409H]

If that CALL resulted in an error, the NZ FLAG (Not Zero) will have been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

56D2

POP BC

Restore the Logical File Number held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

56D3

LD L,B

Set HL to point to the applicable file by copying the logical file number (held in Register B) into the LSB of the HIT pointer (i.e. Register L).

56D4

LD (HL),00H

Place a 00H into the HIT at the location of the logical file number being cleared.

56D6

CALL 4AC2H
[4AC2H]

GOSUB to 4AC2H.
NOTE: 4AC2H is the SYS00/SYS routine to write the HIT sector from RAM to diskette.

56D9

JP NZ,4409H
[4409H]

If that CALL resulted in an error, the NZ FLAG (Not Zero) will have been set, JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

56DC

POP AF

Put the value held at the top of the STACK into Register Pair AF, and then remove the entry from the stack.

56DD

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

56DE

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

56DF

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

56E0

JP 5750H
[5750H]

Continue the routine via a JUMP to 5750H.

56E3H - Continuation of "PURGE". Jumped here if the file is active.

56E3

LD A,(58C3H)

Check to see if the user requested to purge all files by fetching the value held in memory location 58C3H and store it into Register A.

56E6

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

56E7

JR NZ,5701H
[5701H]

If the user requested to purge CALL files, then the NZ FLAG (Not Zero) will hav been set, JUMP to 5701H.

56E9

BIT 6,(HL)

Test for a system file by checking Bit Number 6 of Register HL. Z FLAG will be set if that bit is 0, and NZ FLAG will be set if that bit is 1.

56EB

JR Z,56F6H
[56F6H]

If Bit 6 is 0, then this is not a SYSTEM file and the Z FLAG (Zero) will been set, so skip this file by JUMPing to 56F6H to continue checking the file.

56ED

LD A,(58BFH)

Check to see if the user requested to purge SYSTEM FILES by fetching the value held in memory location 58BFH and store it into Register A.

56F0

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

56F1

JP Z,5750H
[5750H]

If the user did not request to purge system files the Z FLAG (Zero) will have been set, JUMP to 5750H.

56F4

JR 5701H
[5701H]

JUMP to 5701H to continue.

56F6H - Continuation of "PURGE".

56F6

BIT 3,(HL)

Check to see if the selected file is invisible by testing Bit Number 3 of Register HL. Z FLAG will be set if that bit is 0, and NZ FLAG will be set if that bit is 1.

56F8

JR Z,5701H
[5701H]

If the Z FLAG (Zero) has been set, then the file is not invisible, so JUMP to 5701H.

56FA

LD A,(58C1H)

If we are here, the file is invisible, so check to see if the user requested to purge invisible files by fetching the value held in memory location 58C1H and store it into Register A.

56FD

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

56FE

JP Z,5750H
[5750H]

If the user did not request to kill invisible files, then the Z FLAG (Zero) will have been set, JUMP to 5750H since we aren't going to kill the current (invisible) file.

5701

CALL 575AH
[575AH]

Get the filename to be killed from the directory entry via a GOSUB to 575AH.

5704

LD HL,5BA2H

Let Register Pair HL equal 5BA2H so as to point to the filename.

5707

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

570A

LD HL,589AH

Let Register Pair HL equal 589AH so as to point to the message " (Y/N/Q) ? ".

570D

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

5710

LD HL,5BD2H

Let Register Pair HL equal 5BD2H to point to a buffer.

5713

LD B,03H

Fetch 3 characters from the keyboard by setting Register B equal 03H.

5715

CALL 0040H
[0040H]

5718

JP C,5791H
[5791H]

If the C FLAG (Carry) has been set then a BREAK was hit, JUMP to 5791H.

571B

LD A,(HL)

Fetch the response received from the user to the Y/N/Q question (held in the memory location pointed to by Register Pair HL) and store it into Register A.

571C

CP 51H

Compare the value held in Register A against 51H (ASCII: Q). Results: If Register A equals Q, the Z FLAG is set; otherwise the NZ FLAG is set.

571E

JP Z,5791H
[5791H]

If the user entered Q to quit, the Z FLAG (Zero) will have been set, JUMP to 5791H.

5721

CP 59H

Compare the value held in Register A against 59H (ASCII: Y). Results: If Register A equals Y, the Z FLAG is set; otherwise the NZ FLAG is set.

5723

JR Z,572BH
[572BH]

If the user entered Y to kill that file, the Z FLAG (Zero) will have been set, JUMP to 572BH.

5725

CP 4EH

Compare the value held in Register A against 4EH (ASCII: N). Results: If Register A equals N, the Z FLAG is set; otherwise the NZ FLAG is set.

5727

JR NZ,5704H
[5704H]

If the user did not enter a "N", then we have an unacceptable character as that was the only valid response left, so JUMP to 5704H.

5729

JR 5750H
[5750H]

JUMP to 5750H to NOT delete the file and continue looping through the files.

572BH - Continuation of "PURGE". Jumped here if we found a file to delete, and the user confirmed to delete it.

572B

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

572E

LD DE,5BA2H

Let Register Pair DE equal 5BA2H which is the File Control Block area in RAM.

5731

LD B,00H

Let Register B equal 00H so that the next routine will set for FULL SECTOR I/O.

5733

LD IYL,00FH
LD IYH,42H

Let Special Index Register IY = 4200H

5739

DEC (IY+00H)

DECrement the value stored in the memory location pointed to by Special Index Register IY by 1.

573C

CALL 4424H
[4424H]

GOSUB to 4424H.
NOTE: 4424H is the SYS00/SYS routine to OPEN A DISK FILE for use. This RST 28H's with a value of 92H so as to call ROUTINE 2 in OVERLAY 3.

573F

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5742

LD A,(5BA3H)

Fetch OPTIONS BYTE from the FILE CONTROL BLOCK (held in memory location 5BA3H) and store it into Register A.

5745

AND 0F8H

MASK the OPTIONS BYTE held in Register A against 0F8H (1111 1000). This has the effect of turning off bits 2, 1, 0, thus setting the file to UNLIMITED ACCESS.

5747

LD (5BA3H),A

Store the OPTIONS BYTE held in Register A back into the FILE CONTROL BLOCK (held in memory location 5BA3H).

574A

LD DE,5BA2H

Let Register Pair DE equal 5BA2H to point to the FILE CONTROL BLOCK.

574D

CALL 442CH
[442CH]

GOSUB to 442CH.
NOTE: 442CH is the SYS00/SYS routine to KILL A DISK FILE. On Entry DE mus tpoint to th ememory location identifying if the file is open or not.

5750

LD HL,(56A2H)

Fetch the HIT POINTER (held in memory location 56A2H) and store it into Register Pair HL.

5753

INC HL

INCrement the HIT POINTER to the next entry by BUMPING HL by 1.

5754

LD (56A2H),HL

Store HIT POINTER into memory location 56A2H.

5757

JP 56A1H
[56A1H]

Loop to the next file by JUMPing to 56A1H.

575AH - SUBroutine in the "PURGE" command which will get the FILESPEC from a DIRECTORY ENTRY.

575A

PUSH HL

Save the directory entry pointer (held in Register Pair HL) to the top of the stack.

575B

LD DE,0005H

Since the filename of a file starts at the 5th byte of a directory entry, let Register Pair DE equal 0005H.

575E

ADD HL,DE

Advance the pointer to the applicable byte of the directory in RAM (pointed to by Register Pair HL) by 5.

575F

LD DE,5BA2H

Let Register Pair DE equal 5BA2H to point to the File Control Block.

5762

LD B,08H

Set up a loop of 8 characters by setting Register B equal to 08H.

5764

LD A,(HL)

Start of loop. Fetch a filename character from the directory entry (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5765

CP 21H

Check to see if there is actually a usable character there by comparing the character we just fetched (held in Register A) against 21H (ASCII: !). Results:

If Register A equals !, the Z FLAG is set.
If A < !, the CARRY FLAG will be set.
if A >= !, the NO CARRY FLAG will be set.

5767

JR C,576EH
[576EH]

If the filename byte in the directory entry is less than ! then we are apparently at the end of the filename and the C FLAG (Carry) will have been set, JUMP to 576EH.

5769

LD (DE),A

Store the filename character held in Register A into the file control block (the memory location pointed to by Register Pair DE).

576A

INC HL

INCrement the pointer in the directory entry (stored in Register Pair HL) by 1.

576B

INC DE

INCrement the pointer in the file control block entry (stored in Register Pair DE) by 1.

576C

DJNZ 5764H
[5764H]

Process up to 8 characters of the filespec by LOOPing back to 5764H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

576E

POP HL

End of loop. Restore the directory entry pointer (held at the top of the stack) into Register Pair HL.

576F

LD BC,000DH

The filespec has been moved, time to process the extension. The extension is 13 bytes into a directory entry, so let Register Pair BC equal 000DH (Decimal: 13).

5772

ADD HL,BC

Advance the pointer to the applicable byte of the directory in RAM (pointed to by Register Pair HL) by 13 to point to the file's extension.

5773

LD A,(HL)

Fetch the first character of the file's extension (held in the memory location pointed to by Register Pair HL) and store it into Register A.

5774

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results: If Register A equals SPACE, the Z FLAG is set; otherwise the NZ FLAG is set.

5776

JR Z,5788H
[5788H]

If there is no extension because there was a SPACE as the first character and Z FLAG (Zero) has been set, JUMP to 5788H.

5778

LD A,2FH

If we are here then we know there is an extension, so add a slash into the file control block by setting Register A equal /.

577A

LD (DE),A

and then storing the / (held in Register A) into the file control block (the memory location pointed to by Register Pair DE).

577B

INC DE

Since we just put in another character into the File Control Block, we need to bump the File Control Block pointer (held in Register DE) by 1.

577C

LD B,03H

Since there are 3 characters max in a filename extension, set Register B equal 03H.

577E

LD A,(HL)

Start of a loop. Fetch a character from the filename's extension from the memory location pointed to by Register Pair HL and store it into Register A.

577F

CP 21H

Check to see if there is actually a usable character there by comparing the character we just fetched (held in Register A) against 21H (ASCII: !). Results:

If Register A equals !, the Z FLAG is set.
If A < !, the CARRY FLAG will be set.
if A >= !, the NO CARRY FLAG will be set.

5781

JR C,5788H
[5788H]

If the filename's extension byte in the directory entry is less than ! then we are apparently at the end of the filename and the C FLAG (Carry) will have been set, JUMP to 5788H.

5783

LD (DE),A

We have a valid extension character in Register A so store it into the FCB at the memory location pointed to by Register Pair DE.

5784

INC HL

INCrement the pointer in the directory entry (stored in Register Pair HL) by 1.

5785

INC DE

INCrement the pointer in the file control block entry (stored in Register Pair DE) by 1.

5786

DJNZ 577EH
[577EH]

Process up to 3 characters of the extension by LOOPing back to 577EH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5788

LD HL,58C6H

End of loop. Let Register Pair HL equal 58C6H to point to the drive number + terminator.

578B

LD BC,0003H

Since a drive number + terminator is 3 bytes, set Register Pair BC equal 0003H.

578E

LDIR

Copy the drive number + terminator from the directory entry into the file control block via LDIR which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

5790

RET

RETurn to the caller.

5791H - Continuation of the "PURGE" Routine - Finish the routine and request system disk if needed.

5791

LD A,(58C5H)

Check to see if the DOS was deleted by fetching the value held in memory location 58C5H and store it into Register A.

5794

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5795

RET Z

If the Z FLAG (Zero) has been set then DOS was not deleted, so we are good to go. RETurn to the caller.

5796

LD A,(58C9H)

We now know that DOS was deleted, and need to get the drive number, so fetch the value held in memory location 58C9H and store it into Register A.

5799

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

579A

RET NZ

If the drive we just modified wasn't :0 then we don't really care if DOS was deleted or not, so as long as it wasn't :0 RETurn to the caller.

579B

LD HL,5885H

We now know that DOS was deleted and from Drive :0 and that we need to prompt for a DOS disk, so first set Register Pair HL equal 5885H to point to the message "INSERT A SYSTEM DISK.".

579E

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

57A1

JP 0049H
[0049H]

Wait for a key press and then RETurn via JUMP to the Model III ROM routine at 0049H which is is the Model III ROM routine to scan the keyboard and wait until a key is pressed, and then return with the key pressed in Register A. BREAK returns 01H.

57A4H - Subroutine in the "PURGE" Routine - Encode the password stored in the memory location pointed to by Register Pair DE; results in Register Pair HL.

57A4

LD HL,0FFFFH

LET Register Pair HL = 0FFFFH (Decimal: -1) as the default.

57A7

LD B,08H

LET Register B = 08H since a password is 8 characters.

The next few instructions skip to the end of the password (pointed to by Register Pair DE) by adding 7 to the LSB (i.e., Register E).

57A9

LD A,E

LET Register A = Register E.

57AA

ADD A,07H

ADD the value 07H to Register A (Results held in Register A).

57AC

LD E,A

LET Register E = Register A.

57AD

JR NC,57B0H

If the NC FLAG (No Carry) is set then we did not move to a new memory page (i.e., need to update D as well), so skip over the next instruction which increments D, and JUMP to 5113H.

57AF

INC D

Bump the value stored in Register D by 1.

At this point, Register Pair DE is now pointing to the END of the password.

57B9

LD A,(DE)

Fetch the value stored at memory location pointed to by Register Pair DE (i.e., 1 character of the 8 character password) and put it into Register A.

57B1

PUSH DE

Save Register DE (i.e., the location in the password string where Register A got the character from) to the top of the stack.

57B2

LD D,A

LET Register D = Register A (i.e., the password character pointed to by (DE)).

57B3

LD E,H

LET Register E = Register H (i.e., the MSB of the password).

57B4

LD A,L

LET Register A = Register L (i.e., the LSB of the password).

57B5

AND 07H

MASK the value of Register A against 07H (0000 0111). This has the effect of turning off bits 7, 6, 5, 4, 3, leaving only bits 2, 1, 0 active.

57B7
57B8
57B9

RRCA
RRCA

Move the bottom 3 bits (2, 1, and 0) to the top 3 bits (7, 6, and 5)

57BA

XOR L

eXclusive OR Register L against Register A to merge the masked Register A with the LSB. The results are stored in Register A.

57BB

LD L,A

LET Register L = Register A (i.e., the new LSB).

57BC

LD H,00H

LET Register H = 00H so that the MSB = 0.

57BE

SBC HL,DE

Let PASSWORD = PASSWORD - DE by subtracting the value stored in Register Pair DE and the carry flag from the value stored in Register Pair HL.

57C0

ADD HL,HL

Let PASSWORD = PASSWORD * 2 by adding the value held in Register Pair HL to Register Pair HL. The results are held in Register Pair HL.

57C1

ADD HL,HL

Let PASSWORD = PASSWORD * 4 by doing that again.

57C2

XOR H

eXclusive OR Register H (i.e., the new MSB) against Register A (i.e., the old LSB). The results are stored in Register A.

57C3

XOR D

eXclusive OR Register D (i.e., the character) against Register A (i.e., the old LSB / new MSB combination). The results are stored in Register A.

57C4

LD D,A

LET Register D = Register A (i.e., the mishmash we just did).

57C5

LD A,L

LET Register A = Register L (i.e., the new MSB).

57C6

ADD HL,HL

Let PASSWORD = PASSWORD * 2 by adding the value held in Register Pair HL to Register Pair HL. The results are held in Register Pair HL.

57C7

XOR H

eXclusive OR Register H (i.e., the NEWER MSB) against Register A (i.e., the prior new MSB). The results are stored in Register A.

57C8

XOR E

eXclusive OR Register E (i.e., the old MSB) against Register A. The results are stored in Register A.

57C9

LD E,A

LET Register E = Register A.

57CA

EX DE,HL

EXchange the value stored in Register Pair HL with the value stored in Register Pair DE so that Register Pair HL now contains the newly encoded password.

57CB

POP DE

Restore Register Pair DE (i.e., the location in the pasword string for the character which was just processed) from the top of the STACK.

57CC

DEC DE

DECrement the value stored in Register Pair DE by 1 to point to the previous character in the password string.

57CD

DJNZ 57B0H

LOOP back to 5113H until Register B is ZERO (i.e., all 8 characters of the password have been processed, in reverse).

57CE
57CF

LD A,H
OR L

The Z-80 does not have a way to check a register pair against 0 easily. So a common trick is to let Register A equal one part of the Register Pair and then to OR that against the other part of the Register Pair. Only if both parts of the register pair were 0 will A be 0.

57D1

RET NZ

If the NZ FLAG (Not Zero) is set, then Register Pair HL (i.e., the password) was not 0, so RETurn to the caller.

57D2

INC L

Bump the value stored in Register L by 1 so we don't have a password of 0.

57D3

RET

RETurn to the caller.

57D4H - Subroutine in the "PURGE" Routine - Delete all System Files.

57D4

LD HL,5878H

Let Register Pair HL equal 5878H to point to the message "SYSTEM FILES".

57D7

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

57DA

LD HL,58C6H

Let Register Pair HL equal 58C6H to point to the drivespec in ASCII.

57DD

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

57E0

LD HL,589AH

Let Register Pair HL equal 589AH to point to the message " (Y/N/Q) ?".

57E3

CALL 021BH
[021BH]

GOSUB to 021BH.
NOTE: 021BH is the Model III ROM routine to display the character at (HL) until a 03H is found.

57E6

LD HL,5BD2H

Let Register Pair HL equal 5BD2H to point to a buffer.

57E9

LD B,03H

Fetch 3 characters from the keyboard by setting Register B equal 03H.

57EB

CALL 0040H
[0040H]

57EE

LD A,(HL)

Fetch the response received from the user to the Y/N/Q question (held in the memory location pointed to by Register Pair HL) and store it into Register A.

57EF

CP 4EH

Compare the value held in Register A against 4EH (ASCII: N). Results: If Register A equals N, the Z FLAG is set; otherwise the NZ FLAG is set.

57F1

JR Z,580AH
[580AH]

If the user entered "N" then the Z FLAG (Zero) will have been set, JUMP to 580AH to skip this file.

57F3

CP 51H

Compare the value held in Register A against 51H (ASCII: Q). Results: If Register A equals Q, the Z FLAG is set; otherwise the NZ FLAG is set.

57F5

JR NZ,57FAH
[57FAH]

If the user did not enter a "Q" then skip the next few instructions (which return) and JUMP to 57FAH.

57F7
57F8

INC SP
INC SP

INCrement the value stored in Register Pair SP by 1 to affect the RETurn.

57F9

RET

RETurn to the caller.

57FAH - Continuation of the "PURGE" subroutine to Delete all System Files.

57FA

CP 59H

Compare the value held in Register A against 59H (ASCII: Y). Results: If Register A equals Y, the Z FLAG is set; otherwise the NZ FLAG is set.

57FC

JR NZ,57D4H
[57D4H]

If the user didn't enter a Y either, then we received no valid response to the Y/N/Q inquiry and the NZ FLAG (Not Zero) will have been set, JUMP back to 57D4H to display the Y/N/Q prompt again.

57FE

LD HL,43E0H

Let Register Pair HL equal 43E0H to point to the SYSTEM FILE DESCRIPTORS.

5801

LD E,(HL)

Fetch the first byte of the SYSTEM FILE DESCRIPTORS (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5802

INC HL

Point HL to the next byte of the SYSTEM FILE DESCRIPTORS.

5803

LD D,(HL)

Fetch the second byte of the SYSTEM FILE DESCRIPTORS (held in the memory location pointed to by Register Pair HL) and store it into Register E.

5804

DEC HL

Point HL to the first byte of the SYSTEM FILE DESCRIPTORS.

5805

INC DE

INCrement the two-byte SYSTEM FILE DESCRIPTOR held in Register Pair DE by 1.

5806
5806

LD A,D
OR E

5808

JR NZ,580FH
[580FH]

If descriptor was FF (exists) the NZ FLAG (Not Zero) will have been set, JUMP to 580FH to continue.

580A

XOR A

Set Register A to ZERO and clear all Flags.

580B

LD (58C5H),A

Store the a 00H into memory location 58C5H to clear the SYSTEM DELETE FLAG.

580E

RET

RETurn to the caller.

580FH - Continuation of the "PURGE" subroutine to Delete all System Files.

580F

LD DE,43E1H

Let Register Pair DE equal 43E1H which is the pointer to the SYSTEM FILE DESCRIPTORs.

5812

LD BC,001FH

Let Register Pair BC equal 001FH to clear 31 sets of descriptors.

5815

LD (HL),0FFH

Store 0FFH's into the memory location pointed to by Register Pair HL.

5817

LDIR

Set all 31 descriptors to FFH via LDIR which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

5819

LD A,(58C9H)

Fetch the drive number (held in memory location 58C9H) and store it into Register A.

581C

LD C,A

Since SYS00/SYS Disk I/O calls usually require Register C to contain the drive number, copy the drive number (held in Register A) into Register C.

581D

CALL 4AC2H
[4AC2H]

GOSUB to 4AC2H.
NOTE: 4AC2H is the SYS00/SYS routine to write the HIT sector from RAM to diskette.

5820

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5823

LD IX,4D00H

Let Special Index Register Pair IX equal 4D00H.
NOTE: 4D00H is a memory buffer (referred to as Memory Buffer 2) where the GAT TABLE is stored in RAM.

5827

LD (IX+00H),01H

Free the entire track 0, except the BOOT sector, by storing a 00H into 1st byte of the GAT Table in RAM (pointed to by Special Index Register Pair IX+00H).

582B

LD (IX+01H),00H

Free the entire track 1 by storing a 00H into the 2nd byte of the GAT in RAM (pointed to by Special Index Register Pair IX+01H).

582F

LD A,(IX+02H)

To clear track 2 we need to do a little math because it isn't entirely a SYSTEM track. Fetch the value of the 3rd byte of the GAT in RAM (pointed to by Special Index Register Pair IX+02H).

5832

AND 0FCH

MASK the 3rd byte of the GAT against 0FCH (1111 1100). This has the effect of turning off bits 1, 0.

5834

LD (IX+02H),A

Free the system parts on track 2 by storing a the masked byte into the 3rd byte of the GAT in RAM (pointed to by Special Index Register Pair IX+02H).

5837

LD (IX+0FH),00H

Free the entire track 15 by storing a 00H into the 16th byte of the GAT in RAM (pointed to by Special Index Register Pair IX+0FH).

583B

LD (IX+10H),00H

Free the entire track 16 by storing a 00H into the 17th byte of the GAT in RAM (pointed to by Special Index Register Pair IX+10H).

583F

LD (IX+12H),00H

Free the entire track 18 by storing a 00H into the 19th byte of the GAT in RAM (pointed to by Special Index Register Pair IX+12H).

5843

LD (IX+13H),00H

Free the entire track 19 by storing a 00H into the 20th byte of the GAT in RAM (pointed to by Special Index Register Pair IX+13H).

5847

LD (IX+14H),00H

Free the entire track 20 by storing a 00H into the 21st byte of the GAT in RAM (pointed to by Special Index Register Pair IX+13H).

584B

LD A,(IX+15H)

To clear track 21 we need to do a little math because it isn't entirely a SYSTEM track. Fetch the value of the 22nd byte of the GAT in RAM (pointed to by Special Index Register Pair IX+15H).

584E

AND 0F0H

MASK the 22nd byte of the GAT against 0FCH (1111 1100). This has the effect of turning off bits 1, 0.

5850

LD (IX+15H),A

Free the system parts on track 21 by storing a the masked byte into the 22nd byte of the GAT in RAM (pointed to by Special Index Register Pair IX+15H).

5853

CALL 4A9BH
[4A9BH]

GOSUB to 4A9BH.
NOTE: 4A9BH is the SYS00/SYS routine to to write the GAT sector from RAM to diskette.

5856

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

We now need to write out the DUMMY system (to display the need for a SYSTEM disk).

5859

LD DE,0002H

Let Register Pair DE equal 0002H since a call to 47F7H requires DE point to the TRACK and SECTOR to be written.

585C

LD HL,5F00H

Let Register Pair HL equal 5F00H since a call to 47F7H requires HL point to a buffer.

585F

CALL 45F7H
[45F7H]

GOSUB to 45F7H which is the SYS00/SYS routine to WRITE A SECTOR TO DISK.

5862

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

5865

RET

RETurn to the caller.

5866H - "PURGE" Command Message and Byte Storage.

5866

DEFM 'Master Password? ' + 03H

5878

DEFM 'System Files' + 03H

5885

DEFM 'Insert a SYSTEM disk' + 0DH

589A

DEFM ' (Y/N/Q) ? ' + 03H

5866H - "PURGE" Command Parameter Table.

58A6

DEFM 'SYS '

58AE

DEFM 'INV '

58B6

DEFM 'ALL '

58BE

DEFB 00H

End of table delimeter

58BFH - "PURGE" Command Message and Byte Storage.

58BF

DEFW 0000H

Flag for SYS Option

58C1

DEFW 0000H

Flag for INV Option

58C3

DEFW 0000H

Flag for ALL Option

58C5

DEFB 00H

Flag for DELETE ALL DOS SYSTEM Files

58C6

DEFM ":N" + 0DH

58C9

DEFB 00H

Drive Number for the PURGE Command

58CA

DEFW 0000H

Hashed Master Password Supplied by the User

58CCH - "LIST" Command.

58CC

LD DE,5BA2H

Let Register Pair DE equal 5BA2H, which will be a buffer to hold a file control block.

58CF

CALL 441CH
[441CH]

GOSUB to 441CH.
NOTE: 441CH is the SYS00/SYS routine to CHECK THE SYNTAX OF A FILESPEC before for use. This RST 28H's with a value of C1H so as to call ROUTINE 4 in OVERLAY 1.

58D2

JP NZ,521DH
[521DH]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 521DH.

58D5

PUSH HL

Save the pointer to the current character of the COMMAND LINE (Register Pair HL) to the top of the stack.

58D6

LD HL,0000H

Let Register Pair HL equal 0000H to zero the current record number.

58D9

LD (5B04H),HL

Store the 0000H (held in Register Pair HL) into memory location 5B04H to zer the current record number.

58DC

LD DE,5BA2H

Let Register Pair DE equal 5BA2H, which will be a buffer to hold a file control block.

58DF

LD HL,5B13H

Let Register Pair HL equal 5B13H which will be a buffer to hold a filename.

58E2

LD B,19H

Prepare for a loop of 25 characters by setting Register B to 19H.

58E4

LD A,(DE)

Fetch a character from the FCB (which will be the filename portion of the FCB) held in the memory location pointed to by Register Pair DE and store it into Register A.

58E5

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results:

If Register A equals SPACE, the Z FLAG is set.
If A < SPACE, the CARRY FLAG will be set.
if A >= SPACE, the NO CARRY FLAG will be set.

58E7

JR C,58EEH
[58EEH]

If the current character of the filename held in the FCB < SPACE then we have run out of valid characters to process and the C FLAG (Carry) will have been set, JUMP to 58EEH.

58E9

LD (HL),A

Store the validated character from the filename from the FCB (held in Register A) into the filename buffer (i.e., the memory location pointed to by Register Pair HL).

58EA

INC HL

INCrement the filename buffer pointer (stored in Register Pair HL) by 1.

58EB

INC DE

INCrement the pointer to the filename in the FCB (stored in Register Pair DE) by 1.

58EC

DJNZ 58E4H
[58E4H]

LOOP back to 58E4H, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

We are here either because of a pass through completion of 25 characters or because we hit a character which was not valid.

58EE

LD (HL),09H

Store an ASCII TAB into the filename buffer pointed to by Register Pair HL.

58F0

INC HL

INCrement the filename buffer pointer (stored in Register Pair HL) by 1.

58F1

LD (HL),03H

Store an 03H terminator into the filename buffer pointed to by Register Pair HL.

58F3

POP HL

Save the pointer to the current character of the COMMAND LINE (held at the top of the stack) into Register Pair HL.

58F4

LD DE,5B89H

Let Register Pair DE equal 5B89H to point to the valid parameter table for LIST command parameters.

58F7

CALL 4454H
[4454H]

GOSUB to 4454H.
NOTE: 4454H is the DOS PARAMETER STRING PARSE routine. It decodes DOS LIBRARY parameters.

58FA

JP NZ,5219H
[5219H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 5219H to display an ILLEGAL PARAMETER error and exit via a JUMP to 5223H.

58FD

LD DE,5BA2H

Let Register Pair DE equal 5BA2H, which will be a buffer to hold a file control block.

5900

LD HL,5D00H

Let Register Pair HL equal 5D00H for a FILE BUFFER.

5903

LD B,00H

Let Register B equal 00H so that the next routine will set for FULL SECTOR I/O.

5905

CALL 4424H
[4424H]

GOSUB to 4424H.
NOTE: 4424H is the SYS00/SYS routine to OPEN A DISK FILE for use. This RST 28H's with a value of 92H so as to call ROUTINE 2 in OVERLAY 3.

5908

JP NZ,4409H
[4409H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

590B

LD A,(5BABH)

Fetch the LOGICAL RECORD LENGTH of the selected file (held in memory location 5BABH) and store it into Register A.

590E

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

590F

JR NZ,591EH
[591EH]

If we were NOT set for FULL SECTOR I/O the the NZ FLAG (Not Zero) will have been set, skip the next few instrutions which prepare for a 256 byte LRL by JUMPing over them to 591EH.

5911

LD HL,5B42H

Let Register Pair HL equal 5B42H to point to the text "256".

5914

LD DE,5B32H

Let Register Pair DE equal 5B32H to point to the middle of the "LRL = nnn" message.

5917

LD BC,0003H

Let Register Pair BC equal 0003H to loop for the 3 characters of "256".

591A

LDIR

591C

JR 5938H
[5938H]

JUMP to 5938H to continue.

591EH - Continuation "LIST" Command; jumped here if the LRL is not 256.

591E

LD HL,5B32H

Let Register Pair DE equal 5B32H to point to the middle of the "LRL = nnn" message.

5921

CP 0C8H

Compare the value held in Register A against C8H (Decimal: 200). Results:

If Register A equals a LRL of 200, the Z FLAG is set.
If A < a LRL of 200, the CARRY FLAG will be set.
if A >= a LRL of 200, the NO CARRY FLAG will be set.

5923

JR C,592CH
[592CH]

If the LRL is less than 200, JUMP to 592CH.

5925

LD (HL),32H

Since the LRL is at least 200, fill the first slot of the "nnn" with a "2".

5927

INC HL

INCrement HL to point to the 2nd n character in the "LRL = nnn" message.

5928

SUB 0C8H

SUBtract 200 from Register A so that any additional routine processing the LRL is working with a number less than 200.

592A

JR 5935H
[5935H]

JUMP to 5935H.

592CH - Continuation "LIST" Command; jumped here if the LRL is less than 200.

592C

CP 64H

Compare the value held in Register A against 64H (Decimal: 100). Results:

If the LRL (held in Register A) equals 100, the Z FLAG is set.
If the LRL (held in Register A) < 100, the CARRY FLAG will be set.
if If the LRL (held in Register A) >= 100 the NO CARRY FLAG will be set.

592E

JR C,5935H
[5935H]

If the LRL is less than 100, JUMP to 5935H.

5930

LD (HL),31H

Since the LRL is at least 100, fill the first slot of the "nnn" with a "1".

5932

INC HL

INCrement HL to point to the 2nd n character in the "LRL = nnn" message.

5933

SUB 64H

SUBtract 100 from Register A so that any additional routine processing the LRL is working with a number less than 100.

5935H - Continuation "LIST" Command; jumped here if first digit of the LRL was "1" or "2".

5935

CALL 529DH
[529DH]

Store the remaining 2 digits of the LRL via a GOSUB to 529DH.

5938H - Continuation "LIST" Command; jumped here to deal with the tens and ones position number of the LRL.

5938

LD BC,(5B06H)

Fetch the value held in memory location 5B06H and 5B07H to see if the LIST command is to be output in ASCII and store it into Register Pair BC.

593C
593C

LD A,B
OR C

Since the Z-80 cannot test Register Pair BC against zero, the common trick is to set Register A to equal to Register B, and then OR A against Register C. Only if both Register B and Register C were zero can the Z FLAG be set.

593E

JR Z,594BH
[594BH]

If the Z FLAG (Zero) has been set, then we are not outputting in ASCII FORMAT, so JUMP to 594BH.

5940

LD HL,5B89H

Let Register Pair HL equal 5B89H, to point to the word "ASCII".

5943

LD DE,5B3CH

Let Register Pair DE equal 5B3CH, to point to the message "REC = 00000".

5946

LD BC,0005H

Since there are 5 0's to replace, set Register Pair BC equal 0005H.

5949

LDIR

Replace the "00000" with "ASCII" via a LDIR which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

594B

CALL 01C9H
[01C9H]

GOSUB to 01C9H.
NOTE: 01C9H is the Model III ROM routine to to CLEAR THE SCREEN and RETurn.

594E

CALL 5AA5H
[5AA5H]

Generate the LIST header via a GOSUB to 5AA5H.

5951

LD A,02H

We will want to protect the top 2 lines of the screen during the LIST so set Register A equal 02H.

5953

LD (4214H),A

Scroll protect the top 2 lines of the screen by storing a 2 (held in Register A) into memory location 4214H.

5956

LD BC,(5B06H)

Fetch the value held in memory location 5B06H and 5B07H to see if the LIST command is to be output in ASCII and store it into Register Pair BC.

595A
595A

LD A,B
OR C

595C

JR Z,59B5H
[59B5H]

If the Z FLAG (Zero) has been set, then we are not outputting in ASCII FORMAT, so JUMP to 59B5H.

If we are here then we are outputting in ASCII Format.

595E

LD HL,5B49H

Prepare the LIST to go to a new line by first setting Register Pair HL equal 5B49H.

5961

CALL 5286H
[5286H]

Move to the new line via a GOSUB to 5286H which outputs a text string pointed to by Register Pair HL to the Screen and, if 5277H is set to 0000H, to the Printer as well.

5964

LD DE,5BA2H

Let Register Pair DE equal 5BA2H, which will be a buffer to hold a file control block.

5967

CALL 0013H
[0013H]

596A

JP NZ,5998H
[5998H]

If the NZ FLAG (Not Zero) has been set, meaning that the prior CALL routine returned with an ERROR, then JUMP to 5998H.

596D

AND 7FH

Turn off the highest bit in Register A by MASKing the value of Register A against 7FH (0111 1111).

596F

CP 09H

Compare the value held in Register A against 09H (ASCII: TAB). Results: If Register A equals TAB, the Z FLAG is set; otherwise the NZ FLAG is set.

5971

JR Z,597FH
[597FH]

If the character is a TAB then display it and skip to the next via a JUMP to 597FH.

5973

CP 20H

Compare the value held in Register A against 20H (ASCII: SPACE). Results:

If Register A equals SPACE, the Z FLAG is set.
If A < SPACE, the CARRY FLAG will be set.
if A >= SPACE, the NO CARRY FLAG will be set.

5975

JR NC,597FH
[597FH]

If A >= SPACE then display it and skip to the next via a JUMP to 597FH.

5977

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5979

JR Z,597FH
[597FH]

If the character is a CARRIAGE RETURN then display it and skip to the next via a JUMP to 597FH.

597B

CP 0AH

Compare the value held in Register A against 0AH (ASCII: LINE FEED). Results: If Register A equals LINE FEED, the Z FLAG is set; otherwise the NZ FLAG is set.

597D

JR NZ,598FH
[598FH]

If the character is a LINE FEED skip (and do not display it) via a JUMP to 598FH.

597F

CALL 526FH
[526FH]

Output the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

5982

CP 0DH

Compare the value held in Register A against 0DH (ASCII: CARRIAGE RETURN). Results: If Register A equals CARRIAGE RETURN, the Z FLAG is set; otherwise the NZ FLAG is set.

5984

JR NZ,598FH
[598FH]

If the character is NOT a CARRIAGE RETURN then JUMP to 598FH.

5986

LD BC,(5B08H)

Fetch the value held in memory location 5B08H-5B09H (which indicate if a SLOW display was requested) and store it into Register Pair BC.

598A
598A

LD A,B
OR C

598C

CALL NZ,0060H
[0060H]

If 5B08H does not equal 0, meaning that the user requested a SLOW display, trigger a delay via a GOSUB to 0060H.

598F

CALL 028DH
[028DH]

GOSUB to 028DH.
NOTE: 028DH is the Model III ROM routine to CHECK FOR BREAK. On exit, the NZ FLAG will be set if BREAK was detected.

5992

RET NZ

If the BREAK was hit (and the NZ FLAG (Not Zero) has been set), RETurn to the caller.

5993

CALL 525FH
[525FH]

Check for a shift-"@" PAUSE via a GOSUB to 525FH.

5996

JR 5964H
[5964H]

LOOP BACK to 5964H to process more data.

5998H - Continuation "LIST" Command; jumped here if we got an error retrieving the file from disk. Register A will contain the error code.

5998

CP 1CH

Compare the value held in Register A against 1CH (END OF FILE ERROR). Results: If the error (held in Register A) equals 1CH (for END OF FILE ERROR), the Z FLAG is set; otherwise the NZ FLAG is set.

599A

JR Z,59A3H
[59A3H]

If the Z FLAG (Zero) has been set, handle the ERROR CODE held in Register A via a JUMP to 59A3H.

599C

CP 1DH

Compare the value held in Register A against 1DH (END OF FILE ERROR). Results: If the error (held in Register A) equals 1CH (for END OF FILE ERROR), the Z FLAG is set; otherwise the NZ FLAG is set.

599E

JR Z,59A3H
[59A3H]

If the Z FLAG (Zero) has been set, handle the ERROR CODE held in Register A via a JUMP to 59A3H.

59A0

JP 4409H
[4409H]

JUMP to 4409H.
NOTE: 4409H is the SYS00/SYS routine to process DOS errors.

59A3H - Continuation "LIST" Command; jumped here if the error we got error retrieving the file from disk was 1CH or 1DH.

59A3

LD A,(4020H)

Fetch the value held in memory location 4020H and store it into Register A.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

59A6

AND 3FH

Isolate the column number of where the cursor is on screen by MASKing the value of Register A against 3FH (0011 1111), turning off bits 7 and 6.

59A8

JR Z,59AFH
[59AFH]

If masked cursor position is at the left margin, the Z FLAG (Zero) will have been set, skip the next instructions which move to the left margin via a JUMP to 59AFH.

59AA

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

59AC

CALL 526FH
[526FH]

Move to a new line by outputting the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

59AF

LD HL,5B45H

Let Register Pair HL equal 5B45H which points to the message "EOF".

59B2

JP 5286H
[5286H]

Display the "EOF" and exit via a JUMP to 5286H which outputs a text string pointed to by Register Pair HL to the Screen and, if 5277H is set to 0000H, to the Printer as well.

59B5H - Continuation "LIST" Command; jumped here if the file is to be listed in hex.

59B5

LD HL,5B4BH

Let Register Pair HL equal 5B4BH to point to the message "1...5....10...15...20 ..."

59B8

CALL 5286H
[5286H]

Display that message via a GOSUB to 5286H which outputs a text string pointed to by Register Pair HL to the Screen and, if 5277H is set to 0000H, to the Printer as well.

59BB

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

59BD

CALL 526FH
[526FH]

Move to a new line by outputting the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

59C0

LD A,03H

We need to scroll protect three lines at the top of the screen so set Register A to equal 03H.

59C2

LD (4214H),A

Scroll protect the top 3 lines of the display by storing a 3 into memory location 4214H.

59C5

LD DE,5BA2H

Let Register Pair DE equal 5BA2H, which will be a buffer to hold a file control block.

59C8

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

59CB

CALL 4436H
[4436H]

GOSUB to 4436H.
NOTE: 4436H is the SYS00/SYS vector for 'READ', which reads the record that the disk drive is positioned over.

59CE

JR NZ,5998H
[5998H]

If the NZ FLAG (Not Zero) has been set, JUMP to 5998H.

59D0

CALL 5AA5H
[5AA5H]

Generate the LIST header via a GOSUB to 5AA5H.

59D3

LD HL,(5B04H)

Fetch the record number (held in memory location 5B04H) and store it into Register Pair HL.

59D6

INC HL

INCrement the record number (stored in Register Pair HL) by 1.

59D7

LD (5B04H),HL

Store the bumped record number (held in Register Pair HL) into memory location 5B04H.

59DA

LD A,(5BABH)

Fetch the LRL (held in memory location 5BABH) and store it into Register A.

59DD

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

59DE

JR NZ,59F0H
[59F0H]

If we are not looking at a FULL SECTOR I/O because the LRL was not 0, JUMP to 59F0H.

59E0

LD HL,5D00H

Let Register Pair HL equal 5D00H for a FILE BUFFER.

59E3

LD B,3CH

Since a data line is 60 characters, set Register B to 3CH (Decimal: 60).

59E5

CALL 5A18H
[5A18H]

Output Register B number of characters from the FILE BUFFER via a GOSUB to 5A18H.

59E8

JR Z,59C5H
[59C5H]

If the Z FLAG (Zero) has been set the we need to move to a new disk sector, so JUMP to 59C5H.

59EA

LD DE,003CH

Let Register Pair DE equal 003CH for the next block of 60 characters.

59ED

ADD HL,DE

Position HL to the next 60 character block in the 5D00H file buffer.

59EE

JR 59E3H
[59E3H]

Loop back to 59E3H.

59F0H - Continuation "LIST" Command; jumped here if the file is to be listed in hex BUT we are not in FULL SECTOR I/O mode because the LRL was not 256.

59F0

CP 3DH

Compare the value held in Register A against 3DH (Decimal: 61). Results:

If Register A equals 61, the Z FLAG is set.
If A < 61, the CARRY FLAG will be set.
if A >= 61, the NO CARRY FLAG will be set.

59F2

JR NC,59FDH
[59FDH]

If the LRL is at least 61 (meaning, at least one more line), JUMP to 59FDH.

59F4

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

59F7

LD B,A

Let Register B = the number of bytes left in the LRL (which we know is 60 or less).

59F8

CALL 5A18H
[5A18H]

Output Register B number of characters via a GOSUB to 5A18H.

59FB

JR 59C5H
[59C5H]

Loop Back to 59C5H for the next record.

59FDH - Continuation "LIST" Command; jumped here if the file is to be listed in hex BUT we are not in FULL SECTOR I/O mode AND the LRL is at least 61 characters.

59FD

LD HL,5E00H

Let Register Pair HL equal 5E00H for a FILE BUFFER / DATA STORAGE BUFFER.

5A00

PUSH AF

Save the remaining byte count (held in Register A) to the top of the stack.

5A01

LD B,3CH

Let Register B equal 3CH (Decimal: 60).

5A03

CALL 5A18H
[5A18H]

Output Register B number of characters via a GOSUB to 5A18H.

5A06

POP AF

Restore the remaining byte count from the top of the STACK back into Register Pair AF, and then remove the entry from the stack.

5A07

SUB 3CH

SUBtract the value 3CH from Register A.

5A09

JP C,59C5H
[59C5H]

If the C FLAG (Carry) has been set, JUMP to 59C5H.

5A0C

PUSH AF

Save the remaining byte count (held in Register A) to the top of the stack.

5A0D
5A0F
5A10

LD A,3CH
ADD A,L
LD L,A

Let the location in the file buffer (held in HL) = HL + 60 bytes.

5A11

POP AF

Restore the remaining byte count from the top of the STACK back into Register Pair AF, and then remove the entry from the stack.

5A12

CP 3DH

Compare the remaining byte count (held in Register A) against 3DH (Decimal: 61). Results:

If Register A equals 61, the Z FLAG is set.
If A < 61, the CARRY FLAG will be set.
if A >= 61, the NO CARRY FLAG will be set.

5A14

JR C,59F7H
[59F7H]

If there is 61 bytes or less left, the C FLAG (Carry) will have been set, JUMP to 59F7H to deal with that.

5A16

JR 5A00H
[5A00H]

If there are at least 61 bytes, LOOP back to to 5A00H to keep processing bytes.

5A18H - Output Register B number of characters in ALPHA and HEX. On Entry: HL = the position in the FILE BUFFER to display, B = the number of characters to output

5A18
LD C,03H
We are going to need to make 3 passes so set Register C equal 03H.

5A1A
PUSH BC
Save the number of characters to output (held in Register B) to the top of the stack.

5A1B
PUSH HL
Save the position in the FILE BUFFER to display (held in Register Pair HL) to the top of the stack.

5A1C
LD A,C
Copy the pass counter (held in Register C) into Register A.

5A1D
CP 03H
Check to see if this is the FIRST pass by compare the pass counter (held in Register A) against 03H. Results: If Register A equals 03H, the Z FLAG is set; otherwise the NZ FLAG is set.

5A1F
JR NZ,5A36H
      [5A36H]
If this is NOT the first pass, JUMP to 5A36H.

5A21
LD A,(HL)
Fetch the character to output from (HL) into Register A.

5A22
CP 20H
Test if this is a control character by comparing it against 20H. If the character is < 20H, the CARRY FLAG will be set ...

5A24
JR C,5A2AH
     [5A2AH]
... and we will JUMP to 5A2AH to display a ".".

5A26
CP 7BH
Test if this is a regular character by comparing it against 7BH. If the character is < 7BH, the CARRY FLAG will be set ...

5A28
JR C,5A2CH
     [5A2CH]
... and we will JUMP to 5A2AH to display the character held in Register A.

5A2A
LD A,2EH
Let Register A equal to a ..

5A2C
CALL 526FH
     [526FH]
Outputting the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

5A2F
INC L
Move to the next character by INCrementing the value stored in Register L by 1.

5A30
JR Z,5A56H
     [5A56H]
Did we move past the end of the sector? If Register L hit 0 then we did, and so we must jump to 5A56H.

5A32
DJNZ 5A21H
     [5A21H]
LOOP back to 5A21H for "B" characters, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5A34
JR 5A56H
   [5A56H]
Continue the routine by JUMPing to 5A56H.

5A36H - Output Register B number of characters in ALPHA and HEX; SECOND PASS.

5A36

CP 02H

Check to see if this is the FIRST pass by compare the pass counter (held in Register A) against 02H. Results: If Register A equals 02H, the Z FLAG is set; otherwise the NZ FLAG is set.

5A38

JR NZ,5A4DH
[5A4DH]

If this is NOT the second pass, JUMP to 5A4DH.

5A3A

LD A,(HL)

Fetch the character to output from (HL) into Register A.

5A3B
5A3D
5A3F
5A41

SRL A
SRL A
SRL A
SRL A

Shift the LEFT NYBBLE (xxxx nnnn) to the RIGHT NYBBLE (0000 xxxx).

5A43

CALL 5293H
[5293H]

Output Register A (which will be the prior LEFT NYBBLE) in HEX via a GOSUB to 5293H.

5A46

INC L

Move to the next character by INCrementing the value stored in Register L by 1.

5A47

JR Z,5A56H
[5A56H]

Did we move past the end of the sector? If Register L hit 0 then we did, and so we must jump to 5A56H.

5A49

DJNZ 5A3AH
[5A3AH]

LOOP back to 5A3AH for "B" characters, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5A4B

JR 5A56H
[5A56H]

Continue the routine by JUMPing to 5A56H.

5A4DH - Output Register B number of characters in ALPHA and HEX; THIRD PASS.

5A4D

LD A,(HL)

Fetch the character to output from (HL) into Register A.

5A4E

CALL 5293H
[5293H]

Output Register A (which will be the RIGHT NYBBLE) in HEX via a GOSUB to 5293H.

5A51

INC L

Move to the next character by INCrementing the value stored in Register L by 1.

5A52

JR Z,5A56H
[5A56H]

Did we move past the end of the sector? If Register L hit 0 then we did, and so we must jump to 5A56H.

5A54

DJNZ 5A4DH
[5A4DH]

LOOP back to 5A4DH for "B" characters, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

We have done the 3 passes - the letter, the left nybble, and the right nybble.

5A56

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

5A58

CALL 526FH
[526FH]

Output the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

5A5B

POP DE

Put the DATA ADDRESS (held at the top of the STACK) into Register Pair DE, and then remove the entry from the stack.

5A5C

POP BC

Put the BYTE TO DISPLAY COUNT and PASS COUNTER (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

5A5D

DEC C

DECrement the pass counter (stored in Register C) by 1.

5A5E

JR Z,5A63H
[5A63H]

If we have done all passes, JUMP to 5A63H.

5A60

EX DE,HL

Put the DATA ADDRESS into Register Pair HL.

5A61

JR 5A1AH
[5A1AH]

LOOP back to 5A1AH for another pass.

5A63H - Output Register B number of characters in ALPHA and HEX; after 3 passes.

5A63

LD A,L

Copy the position in the DATA RECORD (held in Register L) into Register A.

5A64

EX DE,HL

Reset the DATA RECORD address.

5A65

OR A

Determine if we are at the end of the sector by setting the FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5A66

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5A67

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

5A68

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

5A69

PUSH AF

Save the contents of Register Pair AF to the top of the stack.

5A6A

LD B,3CH

We want to output 60 "-"'s so Let Register B equal 3CH (Decimal: 60).

5A6C

LD A,2DH

Let Register A equal 2DH (ASCII: -).

5A6E

PUSH BC

Save the dash counter (held in Register B) to the top of the stack.

5A6F

CALL 526FH
[526FH]

Output the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

5A72

POP BC

Put the dash counter (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

5A73

DJNZ 5A6CH
[5A6CH]

LOOP back to 5A6CH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5A75

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

5A77

CALL 526FH
[526FH]

Output the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

5A7A

LD BC,(5B08H)

Fetch the value held in memory location 5B08H-5B09H (which indicate if a SLOW display was requested) and store it into Register Pair BC.

5A7E
5A7E

LD A,B
OR C

5A80

CALL NZ,0060H
[0060H]

If 5B08H does not equal 0, meaning that the user requested a SLOW display, trigger a delay via a GOSUB to 0060H.

5A83

CALL 525FH
[525FH]

Check for a shift-"@" PAUSE via a GOSUB to 525FH.

5A86

CALL 028DH
[028DH]

GOSUB to 028DH.
NOTE: 028DH is the Model III ROM routine to CHECK FOR BREAK. On exit, the NZ FLAG will be set if BREAK was detected.

5A89

JP NZ,4030H
[4030H]

If the BREAK was hit then the NZ FLAG (Not Zero) will have been set, JUMP to 4030H.
NOTE: 4030H is the OPERATION ABORTED routine. Routine runs, displays an error, and returns to the DOS PROMPT.

5A8C

POP AF

Put the value held at the top of the STACK into Register Pair AF, and then remove the entry from the stack.

5A8D

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5A8E

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5A8F

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

5A90

RET

RETurn to the caller.

5A91H - Part of the routine to output a Byte held in Register A to the Screen and, if 5277H is set to 0000H, to the Printer; JUMPED to if we have a TAB character.

5A91

LD A,(4020H)

Fetch the value held in memory location 4020H and store it into Register A.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

The next 3 instructions are fancy math to take a screen position and determine how many spaces are needed to get to the next tab stop.

5A94

CPL

Reverse each bit in Register A (which is the same as NOT).

5A95

AND 07H

Isolate the lowest 3 bits by MASKing the value of Register A against 07H (0000 0111).

5A97

INC A

INCrement the value stored in Register A by 1.

5A98

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5A99

LD B,A

Set the tab counter by copying the contents of Register A into Register B.

5A9A

PUSH BC

Save the counter (held in Register Pair BC) to the top of the stack.

5A9B

LD A,20H

Let Register A equal 20H (ASCII: SPACE).

5A9D

CALL 526FH
[526FH]

Output the character held in Register A to the screen and, if applicable, the printer, via a GOSUB to 526FH.

5AA0

POP BC

Restore the counter (held at the top of the STACK) into Register Pair BC, and then remove the entry from the stack.

5AA1

DJNZ 5A9AH
[5A9AH]

LOOP back to 5A9AH, reducing Register B each time, and continue to LOOP until Register B has been reduced to ZERO, in which case, continue with the next instruction.

5AA3

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

5AA4

RET

RETurn to the caller.

5AA5H - Generate the LIST header.

5AA5

PUSH BC

Save the contents of Register Pair BC to the top of the stack.

5AA6

PUSH DE

Save the contents of Register Pair DE to the top of the stack.

5AA7

PUSH HL

Save the contents of Register Pair HL to the top of the stack.

5AA8

LD HL,(4020H)

Fetch the value held in memory location 4020H and store it into Register Pair HL.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

5AAB

LD A,H

Copy the MSB of the cursor position (held in Register H) into Register A.

5AAC

CP 3CH

Check to see if the cursor is in the first quarter of the screen by comparing the value held in Register A against 3CH. NZ will be set if NOT ...

5AAE

JR NZ,5AB9H
[5AB9H]

... at which point we skip the next instructions and JUMP to 5AB9H.

5AB0

LD A,L

Copy the line number that the cursor is on (held in the LSB of the cursor position) into Register A.

5AB1

CP 30H

See if the cursor is after column 48 by comparing the value held in Register A against 30H (Decimal: 48). NC will be set if the column >= 48 ...

5AB3

JR NC,5AB9H
[5AB9H]

... and we will skip the next instructions and also JUMP to 5AB9H.

5AB5

LD DE,0040H

Set Register Pair DE to a full screen line by setting to 0040H (Decimal: 64).

5AB8

ADD HL,DE

Move the cursor one line down by adding a full screen line (held in DE) to the cursor position (held in HL).

5AB9

PUSH HL

Save the new cursor position (held in Register Pair HL) to the top of the stack.

5ABA

LD HL,3C00H

Home the cursor by letting Register Pair HL equal 3C00H.

5ABD

LD (4020H),HL

Store the value held in Register Pair HL into memory location 4020H.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

5AC0

LD BC,(5B06H)

Fetch the value held in memory location 5B06H and 5B07H to see if the LIST command is to be output in ASCII and store it into Register Pair BC.

5AC3
5AC4

LD A,B
OR C

5AC5

JR NZ,5AE1H
[5AE1H]

If ASCII was requested, skip the next instructions and JUMP to 5AE1H.

5AC7

LD HL,(5B04H)

Fetch the record number (held in memory location 5B04H) and store it into Register Pair HL.

5ACA

INC HL

INCrement the value stored in Register Pair HL by 1.

5ACB

CALL 0A9AH
[0A9AH]

GOSUB to 0A9AH.
NOTE: 0A9AH is the Model III ROM routine to STORE AN INTEGER. The value in HL is put into the single precision number storage area of 4121H and is flagged as an INTEGER.

5ACE

XOR A

Set Register A to ZERO and clear all Flags.

5ACF

CALL 1034H
[1034H]

GOSUB to 1034H.
NOTE: 0A9AH is the Model III ROM routine to initializes the input buffer for an ASCII conversion.

5AD2

OR (HL)

Set the NZ Flag.

5AD3

CALL 0FD9H
[0FD9H]

GOSUB to 0FD9H..
NOTE: 0A9AH is the Model III ROM routine to convert the integer value in REG 1 to an ASCII string. Return with register pair HL pointing to the result.

5AD6

LD HL,4131H

Let Register Pair HL equal 4131H which is where the ASCII converted text is stored.

5AD9

LD DE,5B3CH

Let Register Pair DE equal 5B3CH, to point to the message "REC = 00000".

5ADC

LD BC,0005H

Since there are 5 0's to replace, set Register Pair BC equal 0005H.

5ADF

LDIR

Replace the "00000" with the ASCII converted text via a LDIR which transfers a byte of data from the memory location pointed to by HL to the memory location pointed to by DE. Then HL and DE are incremented and BC is decremented. If BC is not zero, this operation is repeated. Interrupts can trigger while this instruction is processing.

5AE1

LD HL,5B0CH

Let Register Pair HL equal 5B0CH to point to the filename and a TAB.

5AE4

CALL 5286H
[5286H]

GOSUB to 5286H which outputs a text string pointed to by Register Pair HL to the Screen and, if 5277H is set to 0000H, to the Printer as well.

5AE7

LD HL,3C20H

Position the cursor to position 32 by setting Register Pair HL equal 3C20H.

5AEA

LD (4020H),HL

Store the value held in Register Pair HL into memory location 4020H.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

5AED

LD HL,5B2CH

Let Register Pair HL equal 5B2CH to point to "LRL = NNNN REC = NNNNN".

5AF0

CALL 5286H
[5286H]

GOSUB to 5286H which outputs a text string pointed to by Register Pair HL to the Screen and, if 5277H is set to 0000H, to the Printer as well.

5AF3

LD A,(5277H)

Fetch the send-List-to-printer-too flag (held in memory location 5277H) and store it into Register A.

5AF6

OR A

Since a LD command does not set any FLAGS, Set FLAGS based on the contents of Register A (and, in all events, clear the CARRY FLAG).

5AF7

LD A,0DH

Let Register A equal 0DH (ASCII: CARRIAGE RETURN).

5AF9

CALL NZ,003BH
[003BH]

If the NZ FLAG (Not Zero) has been set, GOSUB to 003BH.
NOTE: 003BH is the Model III ROM routine to write the byte held in Register A to the printer, including waiting for the printer to be available OR getting a BREAK. Uses Register Pair DE.

5AFC

POP HL

Restore the cursor position (held at the top of the STACK) into Register Pair HL, and then remove the entry from the stack.

5AFD

LD (4020H),HL

Store the value held in Register Pair HL into memory location 4020H.
NOTE: 4020H is the storage location for the CURSOR POSITION ON SCREEN.

5B00

POP HL

Put the value held at the top of the STACK into Register Pair HL, and then remove the entry from the stack.

5B01

POP DE

Put the value held at the top of the STACK into Register Pair DE, and then remove the entry from the stack.

5B02

POP BC

Put the value held at the top of the STACK into Register Pair BC, and then remove the entry from the stack.

5B03

RET

RETurn to the caller.

5B04H - "LIST" command MESSAGE and BYTE STORAGE.

5B04

DEFW 0000H

Record Number storage space during a HEX dump.

5B06

DEFW 0000H

ASCII Format Flag

5B08

DEFW 0000H

Slow List Flag

5B0A

DEFW 0000H

Doesn't seem to be used.

5B0C

DEFM "FILE = FILENAME/EXT:D" + 09H + 03H

5B2C

DEFM "LRL = 00 " + 09H + "REC = 00000" + 03H

5B42

DEFM "256"

Full Sector LRL

5B45

DEFM "EOF" + 0DH

End of Text File Message

5B49

DEFW 0AH 0DH

Line Feed / Carriage Return.

5B4C

DEFM "1...5....10...15...20...25...30 ... 60" + 0DH

5B89H - "LIST" command PARAMETER TABLE.

5B89

DEFM "ASCII "

5B91

DEFM "SLOW "

5B99

DEFM "PRT "

5BA1

DEFB 00H

End of Table

5BA2H - General BYTE STORAGE.

5BA2

DEFS 60H

97 byte storage location, used mostly for File Control Block storage.

5D00

DEFS FFH

256 byte storage location, used mostly as a Disk I/O Buffer for SYSTEM Use.

5E00

DEFS FFH

256 byte storage location, used mostly as a Disk I/O Buffer for Program Use.

5F00H - Dummy image for a system if PURGE killed all the system files.

5F00

LD BC,0021H

Set up for a code block of 33 bytes

5F02

ORG 4D00H

Loading address will be 4D00H

5F04

(4D00H) LD A,17H

Prepare to LARGE CHARACTERS

5F06

(4D02H) CALL 0033H

Display the 17H held in Register A

5F09

(4D05H) LD HL, 4D0DH

Point to "NOT A SYSTEM DISK" message

5F0C

(4D08H) CALL 021BH

Display "NOT A SYSTEM DISK" message

5F0F

(4D0BH) JR 4D0FH

Infinite Loop

5F11

(4D0DH) DEFM "NOT A SYSTEM DISK" + 0DH

5F23

02H 02H

EXECUTION ADDRESS of 2 BYTES follows

5F25

00 4DH

Execute at 4D00H