TRS-80 DOS - NEWDOS/80 v2.0 for the Model I - SYS6/SYS Disassembled

SYS6/SYS

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NEWDOS/80 v2.0 SYS6/SYS Disassembly - FORMAT, COPY and APPEND (Model I)

SYS6/SYS is the overlay that carries out the library commands FORMAT, COPY and APPEND (manual sections 2.22, 2.14 and 2.2). NEWDOS/80 has no BACKUP program: a diskette is backed up with COPY format 5 (sector by sector) or format 6 (file by file, CBF). SYS6 is far larger than the overlay area. Its 37 load records fill four address ranges, 4D00H-5185H, 5200H-6484H, 64A3H-65A7H and 65B7H-6FF9H (8,787 bytes), and its transfer address is 4D00H. SYS1 loads it with RST 28H code 28H (FORMAT), 48H (COPY) or 68H (APPEND), and 4D00H sends each code to its command.

The file on the system diskette has the mandatory zaps up to zap 085 applied (see Zaps). The page shows every byte once, in address order; bytes that are not in the file are shown as DEFS rows without a byte column.

Commands and Program Flow

Memory Use

Diskette Control Blocks and Swapping

PDRIVE Records

Diskettes with TI Flag M

Option Flags

Zaps

SYS0 routines: 4409H (error exit), 4420H/4424H (open), 4428H (close), 4436H (read), 4439H (write), 443CH (write with verify), 4448H (position to EOF), 4467H (display a message), 4470H (date), 45B5H (upper case), 46BDH (inside the FDC routine, from the track writing code), 4745H/4747H (FDC Type I commands), 4750H, 4767H, 4773H/4776H/476EH (select a drive), 47E3H (delay), 47ECH (wait for a diskette), 490AH/491FH/4922H/492FH/4936H/494BH (directory sectors), 4980H, 4C92H/4C94H (multiply), 4CB2H/4CB4H (divide), 4CC5H/4CD5H/4CD9H (command line), 4CEDH (delay). The routines at 5C0BH run as part of SYS0 and jump back into it (4813H, 4838H, 4947H, 48B8H, 49DDH). ROM routines: 0013H, 001BH (byte I/O), 002BH (keyboard), 0033H (display).

SYS2 (loaded by 568BH): 4E21H, 4F2EH (build an FCB from a directory entry) and 50CFH (make a directory entry). SYS3: 4E3DH (free the space past the EOF). SYS17 (loaded by 62ADH) is entered at 501CH and calls SYS6 at 5535H, 5784H, 56F9H, 5762H, 552DH and 54CBH when it finishes a diskette COPY.

4D00H - SYS6 Entry: Command Dispatcher

SYS0 loads SYS6 into 4D00H-6FF9H and enters it at 4D00H when SYS1 runs the FORMAT, COPY or APPEND command. Register A holds the RST 28H code from SYS1's command table (bits 5-7 = function number, bits 0-4 = 08H for SYS6): 28H = FORMAT (function 1), 48H = COPY (function 2), 68H = APPEND (function 3). Register Pair HL points to the command line just past the command name.

4D1EH - COPY: Memory Limit and First Drive Number

Entered with Register Pair HL pointing to the COPY parameters. The manual lists six formats. Formats 1 and 2 start with a filespec (2 has a leading $). Formats 3 and 4 start with a drive number and copy one file between two diskettes on that drive. Formats 5 and 6 name two drives and copy a whole diskette (sector by sector, or file by file with CBF). This part sets the memory limit and decides which kind of COPY it is.

4D8BH - COPY Formats 3 and 4: One Drive, Two Diskettes

The source and destination files are on different diskettes in the same drive. 5940H is the set of diskettes that have to be swapped (bit 0 = system, bit 1 = source, bit 2 = destination) and 5941H the set that is mounted now.

4D98H - COPY Formats 1 to 4: Parse the Two Filespecs

Formats 1 and 2 arrive here from 4D36H and formats 3 and 4 from 4D97H, with the command line pointer on the stack.

4DF3H - Build the Destination PDRIVE Sector and the Swap Flags

Called from 4D85H (COPY formats 5 and 6) and 663CH (FORMAT). Reads sector 2 of the system diskette in drive 0 (the PDRIVE sector, 16 bytes for each of drives 0-9) and builds from it at 6EB5H the PDRIVE sector that will be written to the new diskette, then works out which diskettes share a drive.

4E68H - Ask Whether the System Diskette Is Also the Source or Destination

Entered with Register A = 03H (source) or 05H (destination), Register B = the SPDN or DPDN bit and Register Pair HL pointing to the word SOURCE or DESTINATION. If the operator says the system diskette is that diskette, nothing has to be swapped.

4E86H - Unreferenced Code

Nothing jumps or calls to 4E86H. The four bytes would OR Register C into Register D and return.

4E8AH - Copy a Filespec from the Command Line into an FCB

Enter at 4E8AH for the destination FCB at 5B17H, or at 4E8DH with Register Pair DE pointing to any FCB (4DB3H and 6F4EH pass the source FCB at 5AE5H). Register Pair HL points to the filespec in the command line. Up to 32 characters are copied into the FCB, followed by 03H. On return Register Pair DE again points to the FCB and Register Pair HL to the separator that ended the filespec; the Z FLAG is set when the line ended there.

4EA7H - Parse the Options and Check Their Combinations

Entered with Register Pair HL pointing to the command line and Register B holding the command's bit in the option table's attribute bytes (08H = COPY formats 1 to 4 from 4DEBH, 20H = COPY formats 5 and 6 from 4D61H, 40H = FORMAT from 6621H). Each option is looked up at 4F1DH, which records it in the flag bytes 5994H-5997H and jumps back here. At the end of the line the combinations are checked: options that select files need CBF, options that change the diskette's name, date or password cannot be used when CBF copies onto an existing diskette, and the FORMAT DISKETTE? question decides between FMT and NFMT when neither was given.

4F1DH - Look Up One Option in the Option Table

Entered from 4EAAH with Register Pair HL pointing to an option word and Register B holding the command's bit. The table at 505CH is searched for a keyword that matches the start of the word. Each entry holds the keyword, an attribute byte (bit 7 always set; bit 3 allowed in COPY formats 1 to 4, bit 5 in COPY formats 5 and 6, bit 6 in FORMAT; bit 4 a handler address follows; bit 2 four exclusion bytes follow; bits 0-1 the flag byte 5994H-5997H), a flag mask, the optional exclusion bytes and the optional handler address. The option's bit is set, the exclusion bytes are checked against the options already given, the handler (if any) parses the option's value, and the search goes back to 4EA7H.

4F8BH - Option Value Handlers

Called from 4F84H with Register Pair HL pointing to the value that follows the option keyword (and its =). Each one stores the value where the command will use it and returns with Register Pair HL past it. A missing or bad value ends the command with error 2FH at 4F49H. FORMAT also calls 4F95H and 4FE5H for its name and password parameters.

5025H - Encode a Password

Entered with Register Pair HL pointing to a password in the command line. The password (up to 8 letters and digits) is copied to 5960H-5967H, padded with spaces, and turned into the 16-bit code that NEWDOS/80 keeps in the GAT and the directory. Each character is mixed in from the last to the first, and each is set back to a space as it is used, so the buffer is all spaces again at the end. On return Register Pair DE holds the code and Register Pair HL points past the password. A blank password gives 4296H.

505CH - Option Keyword Table (Data)

Searched by 4F1DH. One row for each option: the keyword (including the = of options that take a value), the attribute byte, the flag mask, the four exclusion bytes if attribute bit 2 is set, and the handler address if attribute bit 4 is set. Attribute bits: 7 always set (marks the end of the keyword), 6 allowed in FORMAT, 5 in COPY formats 5 and 6, 3 in COPY formats 1 to 4, 4 handler follows, 2 exclusion bytes follow, 1-0 the flag byte (0 = 5994H, 1 = 5995H, 2 = 5996H, 3 = 5997H). Longer keywords come before shorter ones that start the same way (NDMW, NFMT and NDN= before N). The flag bits are: 5994H bit 7 N, 6 Y, 5 DDND, 4 ODN, 3 KDN, 2 NDN, 1 BDU, 0 KDD; 5995H bit 7 NDMW, 6 CFWO, 5 NDPW, 4 USD, 3 DFO, 2 DDSL, 1 DDGA, 0 ODPW; 5996H bit 7 SN (COPY) or RWF (FORMAT), 6 SPW, 5 UBB, 4 USR, 3 CBF, 2 single file COPY (4DE5H), 1 /ext, 0 UPD; 5997H bit 7 SPDN, 6 DPDN, 5 XLF, 4 ILF, 3 NFMT, 2 FMT, 1 PFST, 0 PFTC.

5186H - End of the Overlay Area (Not in the File)

SYS6's first load block ends at 5185H. These 122 bytes of the DOS overlay area are not loaded. From 4DA6H on the whole overlay area is reused: the command line is copied to 4D3EH, and SYS2, SYS3 or SYS17 is loaded into 4D00H-51FFH (568DH) when SYS6 needs its code.

5200H - Error Exits

Each entry loads a DOS error code into Register A and joins the common exit at 521AH. 5210H is a check used by APPEND: nothing may follow the last parameter.

521AH - Common Exit

521AH ends the command with the error code in Register A: it starts a new line and continues at 521EH, which is also entered directly (with the error code on the stack) when the cursor is already at the start of a line. 5222H is entered with Register Pair HL holding the SYS0 exit to use: 4409H displays the error in Register A, 4030H (error already displayed) and 402DH (no error) go to DOS READY. Every exit switches back to the system diskette in drive 0, puts back the drives' own PDRIVE data if COPY or FORMAT changed it, and clears the FORMAT/COPY bit of 4369H.

5240H - Display a Message and Exit

5240H reports DISKETTE/GAT OVERFLOW. 5243H is entered with Register Pair HL pointing to any message. Either way the message is shown on a new line and the command ends through 4030H (error already displayed), with the clean-up at 5222H.

524EH - COPY by File: Compact the File List and Start Copying

Reached by the JP 524EH at 615FH, in the code at 6157H whose address 60F1H pushes as a return address, once the destination directory entries have been made. The list of files to copy (three bytes for each file, from (5D12H) to (5D14H)) is moved down to 5D16H, so that all memory after it can be used for sector buffers, the source diskette is selected and the first file to copy is opened.

5273H - COPY Engine: Read a Batch of Source Sectors

Used by the diskette COPY (format 5), the COPY by file (format 6, from 5270H) and the single file COPY (formats 1 to 4, from 638FH, entering at 5279H). The free memory from (5D14H) to (593CH) is divided into entries of 258 bytes: a marker byte, a record type byte and the 256 bytes of a sector. As many source sectors as fit are read, then 5324H writes and verifies them. The marker byte is FFH, or in a COPY by file the destination DEC of the file the sector belongs to; the record type is 00H for a normal sector and 06H for a sector written with the directory mark. In a diskette COPY the boot sectors and the drive 0 record of the system data sector are replaced on the way (52DBH).

5324H - COPY Engine: Write the Batch

Writes the entries read by 5291H-5321H (their number is at 5314H) to the destination, then verifies them at 53FBH. In a single file COPY and a COPY by file the whole destination file is first allocated by writing its last sector (5367H), so that it gets its space in one piece. In a COPY by file a change of the marker byte means that the sector belongs to the next file: the sectors written so far are verified and the next destination file is opened.

53FBH - COPY Engine: Verify the Sectors Just Written

Reads back every sector written in this pass into the buffer at (5D10H) (4200H) and compares the record type and the 256 data bytes with the entry it was written from. A sector that does not match is reported with the C, R or P question: R on a read error or wrong record type writes the sector again and checks it again, R on a data mismatch reads it again.

546DH - Write One Sector from a Buffer Entry

Entered with Register Pair HL pointing to an entry (marker byte, record type byte, 256 data bytes) and Index Register IX to the destination FCB. The sector is written at the FCB's NEXT, with the directory mark if its record type is 06H. On a write error C, R or P is asked. Returns the Z FLAG if the sector was written, or the NZ FLAG and Register A = FFH for P. Register Pair HL is kept.

5492H - Step the Destination NEXT Back One Sector

DECrements the destination FCB's NEXT (5B21H), which the last read or write moved on. Register Pair HL is kept.

549CH - COPY Engine: End of the Source

Reached from 52C4H when the source file, the last file to copy, or the source diskette has ended. The last batch is written and verified, then each kind of COPY finishes in its own way: a COPY by file displays DONE, a single file COPY closes the destination file with the source's EOF, and a diskette COPY continues in SYS17.

54D7H - Radio Shack Doubler: Opposite Density for Track 0

Added by zap 076. Called from 68F1H while track 0 of a drive with PDRIVE TI flag K (track 0 in the other density) is formatted, with Index Register IX pointing to the drive's in-memory PDRIVE entry (from 4399H). 54D7H returns the entry's sectors per track in Register D and its drive select byte in Register C, and on a Radio Shack doubler (interface letter D) flips the select byte's density bit. 54ECH (from 6909H) puts the select byte and the disk I/O flags back from Registers C and E.

54F3H - Unreachable Remains of the Old Diskette COPY Ending

Zap 057 moved the code that ended a diskette COPY to SYS17 (501CH-508EH) and zap 076 reused the start of the space. These bytes are the rest of the old code; the same instructions are at SYS17 5051H-508AH. Nothing jumps or calls into 54F3H-552CH, so none of these rows ever runs; the comments say what each instruction would do.

552DH - Display DONE and Exit

Reached when a COPY by file or a FORMAT has finished, and from SYS17 (508CH) at the end of a diskette COPY.

5535H - Switch to a Diskette and Open Its FCB

Enter at 5535H for the destination, or at 5538H with Register Pair HL pointing to a diskette control block. A control block is 10 bytes: +0 the drive number (FFH = not used), +1 the role bit (01H system, 02H source, 04H destination), +2/+3 the FCB address, +4/+5 the address of the working PDRIVE record, +6/+7 the address of the saved original record, +8/+9 the address of the diskette's name for the mount prompt. The diskette is switched in (5585H), Index Register IX is pointed to its FCB, and the FCB is opened if it is not open yet. An open sets the control block's drive number to the drive the file was found on.

5578H - Switch to the Source, Destination or System Diskette

5578H selects the source (594CH), 557DH the destination (5956H), 5582H the system diskette (5942H) and 5585H the control block at Register Pair HL. The drive gets the PDRIVE data needed for that diskette (once 63BDH has saved the drives' own data), the diskette is asked for if another one shares its drive, and the TI flag M patches in SYS0, SYS2 and SYS3 are put in or taken out to match the diskette now in use. Register Pairs HL, DE and BC are kept.

5646H - Save or Restore the PDRIVE Data of All Three Diskettes

5646H calls 5658H for the system, source and destination control blocks that have a drive, with Register B unchanged. 5658H works on the control block at Register Pair HL, with Register B saying what to do: bit 0 clear = the working record (control block +4), set = the saved original (+6); bit 1 clear = copy that record into the drive's PDRIVE entry, set = copy the drive's entry into it; bit 2 set = ignore errors. After the copy SYS0 reselects the drive so that 430AH-4311H follow the entry.

568BH - Load an Overlay into the Overlay Area

568BH loads SYS2. 568DH loads the overlay whose number is in Register A (04H SYS2, 05H SYS3, the code E5H for SYS3 or F3H for SYS17; 00H = none, only switch to the system diskette). The system diskette is switched in first, so that SYS0 can read the overlay from drive 0. The overlay is called as function 7 with Register C = FFH, a sub-function that SYS2, SYS3 and SYS17 do not have: each returns at once with error 2AH, and its code stays in 4D00H-51FFH for SYS6 to call into and patch. The SYS0 dispatcher discards the RST 28H's own return address, so the overlay's RETurn goes straight back to the caller of 568DH.

5699H - Step Through the COPY-by-File List

The file list (from (5D12H) to (5D14H)) holds three bytes for each source file: flags (bit 7 entry used, bit 6 system file, bit 5 to be copied, bit 4 already in the destination directory), the source DEC and the destination DEC. 5699H moves Register Pair HL to the next entry and returns the Z FLAG at the end of the list. 56A2H moves on to the next entry marked to be copied (56A6H tests the current one first) and opens its source file; it returns the Z FLAG when there are no more. 56B9H opens a file from its DEC through SYS2's FCB building code, which 568BH has loaded into the overlay area.

56D4H - Unreferenced Code

Nothing jumps or calls to 56D4H. The four instructions would multiply Register A by the sectors per track at 430EH (IY-72H, with Index Register IY = 4380H from 4D00H) using the SYS0 routine at 4C94H.

56DDH - Directory Sector Helpers

Each routine ends the command at 56FEH on an error. 56DDH reads the directory entry of the file open in the FCB at Index Register IX (Register Pair HL = the entry). 56E2H points Register Pair HL to the entry of the DEC in Register A, reading its sector unless it is already in 4200H and first writing back a changed sector. 56F4H always reads the sector of the DEC in Register A. 56F9H reads the GAT (56FAH: directory sector A). 5701H writes directory sector A from 4200H. 5706H marks the sector in 4200H as changed, 570DH writes it back if one was marked and 5711H writes it back now. Directory sector 0 is the GAT, 1 the HIT and 2 onward the FDE sectors; a DEC's entry is in sector (DEC AND 1FH) + 2, entry DEC / 32.

571BH - Progress Asterisk and Operator Keys

571BH blinks an asterisk in the top right corner of the screen (3C3FH) once for each sector. 572BH reads a key (00H if none) and changes it to upper case. Both then check the keyboard unless NDMW was given: holding the right arrow pauses until ENTER (continue) or the up arrow (cancel) is pressed, and the up arrow cancels the command with error 39H. Register Pair AF is returned as it was (572BH: the key); Register Pairs BC, DE and HL are not changed.

5751H - Free Granules in the GAT

Entered at 5762H with Register Pair HL pointing to a lump's byte in the GAT sector at 4200H, Register C holding the first granule's number in the lump and Register Pair DE the number of granules. The bit of each granule is cleared (free) from there on, lump after lump. If the destination has no more than 96 lumps, the same bits are then cleared in the lockout table 60H bytes further on (5751H, zap 023). Used by FORMAT (6684H) and by SYS17 (5083H) at the end of a diskette COPY. Register Pairs HL, DE and BC are kept.

5784H - Verify the Whole Destination Diskette

Entered with Register Pair DE = the first sector to read and Index Register IX pointing to the destination FCB (5B17H). Every sector from there to the end of the destination diskette is read into 4200H; a sector with the directory mark (error 06H) is correct, any other read error is reported with the C, R or P question. Zap 044 replaced the test of SYSTEM option BM at 5784H with six NOPs, so the verify is always done. Called by FORMAT (6655H) and by SYS17 (5023H) after a diskette COPY.

57C8H - Read, Write and Verify Through the FCB at IX

57C8H reads the sector at the FCB's NEXT (SYS0 4436H), 57CEH writes it (through 5CE4H, zap 032) and 57D4H writes it and reads it back (SYS0 443CH). Register Pair DE is set to Index Register IX, the FCB. Each returns the Z FLAG, or the NZ FLAG with the error code in Register A.

57DAH - Report a Disk Error and Ask C, R or P

Called from 585AH with the error code in Register A. The line ERROR WHILE READING/WRITING/VERIFYING SOURCE/DESTINATION SECTOR n is displayed (n = the FCB's NEXT), and in a COPY by file the file's name. A single file COPY ends here with the error. Otherwise the system diskette is switched in so that SYS4 can display the DOS error message, the operator is asked, the overlay that was in the overlay area is loaded again and the diskette that was in use is switched back. Returns Register A = 1 and the Z FLAG for P, Register A = 2 and the NZ FLAG for R; C ends the command. Register Pairs HL, DE and BC are kept.

584AH - Display the DOS Error and Ask C, R or P

Entered with the error code in Register A. With NDMW the command ends with the error. Otherwise SYS4 displays the error message and returns here, and the operator is asked.

585AH - Disk Error: Retry, Proceed or Cancel

Entered with the error code in Register A and Index Register IX pointing to the FCB. Returns the NZ FLAG if the operator chose R (retry). For P (proceed) the FCB's NEXT is moved past the bad sector and the Z FLAG is returned with Register A = 0. 585EH only moves NEXT on.

5868H - Display the Name of the File Being Copied

Only in a COPY by file (the OR operand at 586AH is set to FFH by 615CH): WITHIN FILE and the name of the file open in the FCB at Index Register IX are displayed and the NZ FLAG is returned. 586FH displays the message at Register Pair HL followed by the file's name.

587EH - Display Routines

587EH displays the message at Register Pair HL and starts a new line; 5881H only starts a new line. 5886H displays Register B characters from Register Pair HL, showing a space for control codes and graphics. 5898H displays Register B spaces. 58A0H displays the NAME/EXT of the directory entry at Register Pair HL. 58BDH displays the character in Register A through the ROM routine at 0033H, keeping Register Pairs DE and AF.

58C5H - Operator Questions

58C5H (not called) would display the message at Register Pair HL before 58C8H. 58C8H asks REPLY C (CANCEL), R (RETRY) OR P (PROCEED): C ends the command with error 39H, P returns Register A = 1 with the Z FLAG, R returns Register A = 2 with the NZ FLAG. With NDMW the command ends at once. 58DEH displays the question at Register Pair HL and asks (Y OR N), returning the Z FLAG for N. 58E4H is the general routine: Register Pair HL points to a list of allowed replies ending with 00H, followed by the prompt text; it returns Register A = the reply's position in the list, with the Z FLAG for the first one.

5909H - Display a Number in Decimal

Displays Register Pair DE (0-65535) without leading zeros, using the table of negative powers of ten at 5933H. The last digit is always shown.

5933H - Variables, Control Blocks and Messages (Data)

The values shown are the ones in the file; the comments give their use at run time. The Variables section of the introduction lists them with their sizes.

5C0BH - Routines Patched into SYS0, SYS2 and SYS3 for TI Flag M

The patch lists at 5B64H-5C09H put jumps to these routines into SYS0, SYS2 and SYS3 while a TI flag M diskette in double density is in use. They run as part of those modules, so their jumps go back into them. 5C0BH replaces the end of SYS0's error code routine at 4737H for the read and write commands: a read that ends without an error now reports error 06H and a read that reports error 06H (the other mark) now has no error, so the meaning of the two data address marks is reversed.

5C80H - Boot Sector Length and Directory Lump (Zap 015)

Called from 52F9H while a diskette COPY replaces sector 0 or 1 with SYS6's boot sector. Register A = the sector number and Register Pair DE = the source sector's data. Returns Register Pair BC = 0100H for the LDIR. For sector 0 the source's directory starting lump (byte 2 of its boot sector) is first copied into the boot sector image, so that the copy finds its directory where the source had it.

5C8EH - Set the Destination Buffer (Zap 024)

Called from 5479H with Register Pair HL pointing to the sector data to write. Makes it the destination FCB's buffer and sets bit 6 of the FCB's second byte, so that SYS0 moves the EOF only when a write goes past it. This stops a rewrite after a verify error from moving the EOF back.

5C96H - Load the Drive Data and Prepare the TI Flag M Patches (Zap 031)

Called from 4D79H and 6389H. After 63B3H has loaded the source and destination PDRIVE data, the TI flag M bit (bit 5 of the flags, +2) and the density bit (bit 0 of the disk I/O flags, +7) of each are checked. Two TI flag M diskettes of different density cannot be used together. If a TI flag M diskette is single density, only a few of the patches are used: the SYS0 set is left out, the SYS2 and SYS3 lists are shortened, and three instructions of the COPY by file code are changed (612DH, 617FH, 61BFH).

5CE4H - Write a Sector (Zap 032)

Reached from 57D1H with Register Pair DE = Index Register IX = the FCB. When the current drive's PDRIVE flags have TI flag M (bit 5 of 430CH), bit 5 of the FCB's third byte is set first, so that SYS0's write does not mark the file updated in its directory entry.

5CF2H - Sectors to Granules (Zap 056)

Called from 6727H with Register Pair HL = a number of sectors and Index Register IX pointing to a working PDRIVE record. Divides by 3 for a diskette with TI flag M in double density, otherwise by 5, the NEWDOS/80 granule size. Returns Register Pair HL = the granules, Register A = the sectors left over.

5D04H - Pointers for the Sector Buffers and File List

Three words that move as COPY runs, with 12 unused bytes before them.

5D16H - COPY by File (Format 6): Format, Read the Include/Exclude List

Reached from 6336H when CBF was given. The destination is formatted first if required (6643H). The source and destination FCBs are then used for real files, so bit 1 of their first bytes is cleared. With ILF= or XLF= the list file (whose filespec 4FACH put into the DOS FCB at 4480H and which 629CH opened) is read into 6491H: one name/ext per line ended by 0DH, lines starting with a semicolon are comments, spaces and empty lines are skipped, each byte is taken modulo 128, and a 0DH on its own ends the list.

5D86H - COPY by File: Choose the Source Files

The source directory's HIT sector (one byte per DEC: 00H free, otherwise the hash code of the file's name) is copied to 6291H and used as the table of candidates. ILF starts from an empty table and puts back the hash code of each listed file; XLF clears each listed file's byte. Then every directory entry is looked at in DEC order; the files that pass the USR, UPD, /ext and system file tests (and the operator's answer with CFWO) get a 3-byte entry in the file list from 6491H: flags (80H, plus bit 6 for a system file that must keep its DEC), the source DEC and the hash code.

5EB3H - COPY by File: Collect the Source Directory Entries

For each file in the list the first 24 bytes of its source directory entry are copied into memory after the list, 24 bytes per file (61D6H), and bit 4 of its list flags is set. When memory runs out the files collected so far are handled on the destination (5EE4H), and the collecting starts again in the same spaces. After the last file 5EE4H is entered once more with 60BFH as its return address.

5EE4H - COPY by File: Make the Destination Directory Entries

Handles the files of the current group (list flag bit 4 set, their 24 source directory bytes collected after the list). With NFMT the destination directory is searched first, entry by entry, for files with the same name: such a file gets the source's EOF and record length and keeps its place, and its space past the new EOF is freed through SYS3 (60A9H). Then, unless DFO was given, the remaining files of the group that are system files kept in place (list flag bit 6) get the same DEC as on the source and their granules at the same distance from the directory; the other files get their entries at 60BFH. The HIT and GAT copies are written back at 6092H.

60A9H - Free the Space Past a File's New EOF

Called from 5F7BH with Register Pair HL pointing to the destination directory entry and Register Pair DE to the destination FCB. SYS0's routine at 4980H saves the registers and runs the code after the CALL (60ACH) as a DOS function with Index Register IX = the FCB. That code hands the entry's EOF to SYS3, whose CLOSE code (still in the overlay area) works out the granules the EOF needs and releases the rest.

60BFH - COPY by File: Give the Remaining Files New Entries

Reached when 5EE4H returns for the last group (5EE0H pushed 60BFH as its return address). Files that did not get a destination entry at 5EE4H get a new one from SYS2 (50CFH), in groups as memory allows: their bytes 0-21 are collected from the source directory (60C8H) and copied into the new entries (60F5H). When only one of the two diskettes has TI flag M, the entry's bytes 1-2 and both password codes are set for the destination's kind and the EOF is adjusted. Then the copying starts (6157H).

6162H - COPY by File Helpers

6162H reads the HIT sector of the current diskette and copies it to 6291H (Register Pair HL = 4200H on return). 616FH copies 256 bytes from Register Pair HL to 4200H, 6172H from Register Pair HL to Register Pair DE. 6178H returns Register A = the number of FDE sectors in the directory and Register C = the directory's granules. 6190H prepares a walk through the file list and the 24-byte spaces.

619DH - Look at a Directory Entry

Entered with Register C = a DEC. The HIT copy at 6291H is checked first: a free entry returns the CARRY FLAG and the NZ FLAG, and on a diskette without TI flag M so do DECs 0 and 1 (BOOT/SYS and DIR/SYS). Otherwise the entry is read and the Z FLAG returned if it is a primary entry in use (bit 4 set, bit 7 clear), with Register Pair HL pointing to it and Register B holding its HIT byte.

61BAH - Step to the Next DEC

Entered with Register C = the DEC and Register Pair HL pointing to the directory's FDE sector count. Steps through the entries in DEC order (the next entry position in the sector, then the next sector) and returns the CARRY FLAG after the last one. On a TI flag M diskette in double density the DECs are numbered 0-4FH one after another.

61CBH - Store a Decimal Digit

Entered with Register A = a number, Register B = 100 or 10 and Register Pair HL pointing to where the digit goes. Nothing is stored if the number is below Register B. Returns Register A = the remainder.

61D6H - Take the Next 24-Byte Space

Returns Register Pair DE = the next 24-byte space after the file list and the CARRY FLAG if it is still below the limit at 61DBH (the top of memory less 24). The pointer at 61D8H moves on by 24 either way. Register Pair HL is kept.

61EAH - TI Flag M Tests

61EAH returns the NZ FLAG if either diskette has TI flag M (bit 5 of the flags at 59B9H or 59C7H), 61F6H if the current drive has (430CH), and 61FCH if exactly one of the two has, with Register A = the destination's flags. 6209H adjusts the EOF middle and high bytes at Register Pair HL when a file with a partly used last sector moves between a diskette with TI flag M and one without.

621CH - Allocate Granules in a GAT Copy

Entered with Register Pair HL = the GAT sector (or its copy), Register E = the lump, Register B = the first granule in it and Register C = the number of granules. Each granule's bit is set. A granule past the destination's last lump, or one already allocated, ends the command with DISKETTE/GAT OVERFLOW (5240H). Used by 6080H and by FORMAT (669FH).

624FH - Compare a Diskette Name

624FH compares the 8 characters at Register Pair HL with the diskette name in the GAT sector at 42D0H; 6254H compares Register B characters at Register Pair HL and Register Pair DE. The Z FLAG is set if they are the same.

6291H - Diskette COPY (Formats 5 and 6): Check the Diskettes

Reached from 4D88H. This code runs once; afterwards 6291H-6390H and 6391H-6490H are reused as copies of the destination's HIT and GAT sectors and 6491H onward for the file list. The list file of ILF or XLF is opened, the overlay needed at the end is loaded (SYS17 for a sector by sector COPY, SYS3 for a COPY by file), the source diskette's GAT is read for its name, date and password (SN, SPW, USD), and the two diskettes are checked against each other before the COPY engine starts.

6377H - Single File COPY (Formats 1 to 4): Find the Drives

Reached from 4DF0H. The drive of each filespec is found (6437H), the drive data and TI flag M patches are set up, SYS2 is loaded for the opens, and the COPY engine is entered.

6392H - Parse the Destination Drive Number

Returns the CARRY FLAG and the drive number in Register A if the parameter at Register Pair HL is a drive number. The number is stored as the destination FCB's drive, the destination drive and at 4DFAH.

63A0H - Parse an Optional Track Count

63A0H stores the destination track count at 64A9H; 63A3H stores it where Register Pair DE points (64A6H for the source). Nothing happens unless the character at Register Pair HL is =. A count of 0 gives error 2FH.

63B3H - Save and Load the Drive Data

Called from 5C96H and 6630H. The PDRIVE entries of the drives used by the system, source and destination diskettes are saved as the originals (63B5H) and copied into each diskette's working record (63BFH). A source or destination given a PDRIVE number with SPDN= or DPDN= takes that record from the system diskette instead (63ECH), and the values typed in the command are put into the working records from the override table (63DAH). From now on each switch installs the diskette's working record.

63ECH - Take a Working Record from the System Diskette's PDRIVE Data

Entered with Register A = a PDRIVE number (FFH = none), Register C = the diskette's drive, Register B = its role bit and Register Pair HL pointing to its working record. The ten bytes of that PDRIVE number's record are copied from the system diskette's PDRIVE sector. A diskette on drive 0 with other PDRIVE data cannot be the system diskette, so it is made a swapped diskette; and when the source and destination share a drive both are swapped.

6424H - Read the System Diskette's PDRIVE Sector

Reads sector 2 of the diskette in drive 0 (the third sector of BOOT/SYS, which holds the PDRIVE records and the SYSTEM options) into 4200H through the FCB at 5B49H, whose drive byte is 00H.

6437H - Find the Drive of a Filespec

Entered with Register Pair DE pointing to a filespec in an FCB and Register Pair BC to its diskette control block. A drive number in the filespec (:d) becomes the control block's drive. In formats 3 and 4 the filespec may not have one, and the drive from the command is added to it instead. In formats 1 and 2 a filespec without a drive number is opened at once (5538H), which finds its drive; that is not allowed with $, SPDN or DPDN.

6485H - Not in the File

The second load block ends at 6484H. 6485H-64A2H is the interleave table of the track format code (6A13H, 6A28H, 6A60H, 6A96H, 6BE9H, 6C57H). From 6491H on, memory is also used for the include/exclude names and the COPY by file list.

64A3H - Override Table (Data)

Used by 63DAH after the PDRIVE data has been loaded: a count, then for each entry the address of a byte in a working PDRIVE record and the value typed in the command (00H = not given).

64B0H - Fill the Sector Buffer

Fills 4200H-42FFH with the byte in Register A. Called from 6675H (FFH, a new GAT sector) and 66C1H (00H, the other directory sectors).

64BAH - Boot Sector Image

These 256 bytes (64BAH-65B9H) are the NEWDOS/80 boot sector. 6700H writes them as sectors 0 and 1 of every diskette FORMAT makes, and a diskette COPY puts them in place of the source's boot sectors (52F6H). The Model I ROM reads sector 0 into 4200H and jumps to 4200H, so each comment starts with the address the byte has there, and the branches link to the rows by that address. FORMAT fills in the drive's values first (6759H): the directory lump (64BCH), the Percom density byte (64C2H), the drive select byte (64CAH, 65B7H), the first sector of SYS0/SYS (64CCH-64CDH), the sectors per side (651BH) and per track (656AH), the first sector number (656FH) and the PDRIVE flags (65B8H, 65B9H). The loader reads SYS0/SYS from track 0 sector 5 into memory record by record and enters it at 4D01H.

65BAH - Directory Entries for BOOT/SYS and DIR/SYS (Data)

The first two directory entries of a new diskette. 66E6H copies them into the first places of directory sectors 2 and 3 (DEC 0 and DEC 1).

65FAH - FORMAT Command

Entered from 4D13H with Register Pair HL pointing to dn2[=tc2],name2,mm/dd/yy,password3[,options]. Null name, date and password parameters give NOTNAMED, the system date and PASSWORD. N is the default when none of N, Y, DDND, ODN, KDN or KDD is given. FORMAT shares the formatting code with COPY formats 5 and 6 (6643H) and ends by displaying DONE (552DH).

6643H - Format the Destination and Write Its System Data

Called from 5D16H (COPY by file) and entered from 6642H (FORMAT). After 67C3H has checked (and with FMT formatted) the diskette, the whole diskette is read back (5784H). Unless BDU was given the system data is then written: the boot sector as sectors 0 and 1, the PDRIVE sector as sector 2, and the directory: a GAT with every granule of the diskette free except BOOT/SYS's and the directory's, a HIT with the hash codes of BOOT/SYS and DIR/SYS, and the FDE sectors with their two entries. Nothing is written after an NFMT or an RWF.

6710H - Work Out a Diskette's Size

6710H does the destination (working record at 59C5H), 6713H the record at Register Pair HL (4D7CH passes the source's at 59B7H). The total sectors (tracks times sectors per track) are stored at +10, the total granules at +12, and the number of lumps at +1. More than 192 lumps gives the PDRIVE conflict message.

674DH - A TI Flag M Diskette Needs BDU

674DH checks whether either diskette has TI flag M; 6751H goes straight to the test of BDU. Without BDU the command ends with the PDRIVE conflict message: SYS6 does not write system data for such a diskette.

6759H - Fill In the Boot Sector and DIR/SYS Entry for the Destination

Called from 67C3H. Puts the destination drive's values into the boot sector image (64BAH-65B9H) and into DIR/SYS's directory entry (65DAH).

67AAH - Write the Boot Sectors or Another Sector

67AAH writes the boot sector at 64BAH as sectors 0 and 1 of the destination. 67B1H writes it as sector Register Pair BC, 67B4H writes the 256 bytes at Register Pair DE as sector Register Pair BC. Each sector is read back (57D4H). The flags returned are those of the last write: the Z FLAG if it went well.

67C3H - Check the Destination Diskette and Format It

Called from 6368H (diskette COPY) and 6643H. Unless Y was given, the destination's first sector and GAT are read to see what is on it: N requires an unformatted diskette, ODN, ODPW and DDND look at its old name, date and password, and KDN/KDD keep them. Then, unless NFMT was given, the diskette is formatted: a partial format with PFST, or every track, with track 0 in the other density for TI flag K.

692FH - Display the Old Diskette Name and Date

692FH displays the word at Register Pair HL (SOURCE or DESTINATION) followed by DISKETTE NAME MISMATCH. 693BH displays the word followed by DISKETTE OLD NAME/DATE = and the name and date from the GAT sector in 4200H.

6959H - Format Tracks

Entered with Register A = the track to stop at, Index Register IX pointing to the destination FCB and the head over the first track (its number at 6AF4H). The drive's kind (the 8 inch and double density bits of 4311H) picks a line of the table at 6CC2H, whose values are stored into the code below. For every track (and each side of a double sided drive) the sector numbers are laid out with the line's interleave and skew (6A13H), the track is written with Write Track (6AA6H), the bytes that fit after the last sector tell whether the drive turns at the right speed (6BCCH), and every sector is read back (6BDEH). A track that fails is tried 10 times. Returns the Z FLAG, or the NZ FLAG with Register A = a DOS error code, or Register A = FFH and Register Pair HL = MOTOR FAST or MOTOR SLOW.

6CA4H - Sectors per Side

Returns Register E = the sectors per track (430EH), halved for a double sided drive.

6CAFH - Step to the Next Track

Steps the head in by one track, or by two for a drive with TI flag L (the double step bit, bit 2 of the disk I/O flags).

6CC2H - Track Format Table (Data)

One 26-byte line for each kind of drive, chosen by 6960H from the 8 inch and double density bits of the disk I/O flags. Bytes: 0 gap byte, 1 address mark lead-in (F5H writes A1H in double density), 2-3 data pattern, 4 gap before each ID field, 5 further zero bytes before the ID mark, 6 gap between the ID and data fields, 7 further zero bytes before the data mark, 8-9 bytes one sector takes on the track, 10-11 bytes a track holds at the nominal speed, 12-13 and 14-15 the tolerances for the speed check, 16 the sector skew from track to track, 17 the interleave, 18-25 not used.

6D61H - FORMAT and COPY Messages (Data)

Displayed through the SYS0 routine at 4467H: 0DH ends a line, 03H ends a message without a new line.

6EB5H - Command Line Parsing Routines

Used only while the command line is parsed: 4DF3H copies the new PDRIVE sector over 6EB5H-6FB4H afterwards. 6EB5H steps to the next parameter: it returns the Z FLAG at the end of the line, the CARRY FLAG if a parameter follows, and the NO CARRY FLAG with the NZ FLAG if the parameter is null (two separators). 6EC0H returns the Z FLAG at the end of the line and otherwise steps over a separator; 6EC4H requires a separator (error 34H).

6ECBH - Parse a Drive Number

Parses an optional colon and a drive number at Register Pair HL. Returns the CARRY FLAG with the number in Register A if the parameter starts with a digit, otherwise the NO CARRY FLAG. 6ED7H is entered with Register Pair HL on the digit (from 6448H). The drive must be available (SYS0 4776H), or the command ends with the error.

6EE2H - Parse a Number of 0-255

6EE2H accepts a decimal number or a hexadecimal one ending in H; 6EE7H a decimal number. Returns the value in Register A (and Register Pair DE) with Register Pair HL past the number. A missing number or one over 255 gives error 2FH. A number over 65535 is not detected (6F47H).

6F4BH - APPEND Command

Entered from 4D0AH (function code 68H) with Register Pair HL pointing to filespec1[,TO],filespec2. filespec2 is opened and positioned to its end, then every byte of filespec1 is read and written to it. The file is closed, which also writes its new EOF. The command returns to SYS1 through 4428H, so the SYS6 exit at 521AH is used only for errors.

6F8FH - Copy a Name

Copies up to 8 letters and digits (the first must be a letter) from Register Pair HL to Register Pair DE and pads the rest of the 8 bytes with spaces. Returns Register A = Register C = the number of characters copied, with the Z FLAG if there were none. Register Pair HL points past the name.

6FB8H - Parse the Date

Parses mm/dd/yy into 598BH, checking each digit against the highest value stored there in the file (2:/4:/::: the month's first digit below 2, the day's below 4, the others below :). A null or missing date parameter takes the system date instead.

6FE5H - Step to the Next Parameter, Skipping TO

Requires a separator (error 34H), then steps over the keyword TO and the separator after it if they are there. A word that only starts with TO (such as a file named TOM) is left alone.