RAM Addresses and Routines

Page Customization

Note:

This page needs some love. There are duplicate lines which may say the same thing. Anyone who is willing to help clean up any part of this page, please speak up! Thanks!

The following keys for DOSes apply:

T1 - Model 1 TRSDOST3 - Model 3 TRSDOS
N1 - Model 1 NEWDOSN3 - Model 3 NEWDOS
L1 - Model 1 LDOSL3 - Model 3 LDOS
M1 - Model 1 MULTIDOSM3 - Model 3 MULTIDOS
D1 - Model 1 DOSPLUSD3 - Model 3 DOSPLUS
All - All DOSes, Model I and Model 3.

RAM Addresses and Routines:

Address
(Hex/Dec/Label)		Model
Code		Description
3000H-37DDH
↳12288-14301		Model 1Reserved. Unused in Model I.
3000H
↳12288		3Write 500 baud cassette leader and sync byte.
3003H
↳12291		3Write 1500 baud cassette leader and sync byte.
3006H
↳12294		3Search for 500 baud cassette leader and sync byte.
3009H
↳12297		3Search for 1500 baud cassette leader and sync byte.
300CH
↳12300		3Turn off cassette.
300FH
↳12303		3Turn on cassette.
3012H
↳12306		3Disk bootstrap routine.
3015H
↳12309		3Power-up routine (jump here from 0002H).
3018H
↳12312		3Maskable interrupt handler.
301BH
↳12315		3RS-232-C initialization driver routine.
301EH
↳12318		3RS-232-C input driver routine.
3021H
↳12321		3RS-232-C output driver routine.
3024H
↳12324		3Keyboard driver routine.
3027H
↳12327		3I/O Route driver routine (not available on Model 4).
3029H
↳12329		3/4To determine if a computer is a Model 3 or Model 4, peek this location.
  • 0 = Model 4
302AH
↳12330		3Part of routine to search for cassette leader and sync byte (jumps here from 0229H).
302DH
↳12333		3Part of LIST command (jumps here from 2B91H).
3030H
↳12336		3BASIC TIME$ function routine.
3033H
↳12339		3$DATE routine (date to 8-character buffer pointed to by HL).
3036H
↳12342		3$TIME routine (time to 8-character buffer pointed to by HL).
3039H
↳12345		3Non-maskable interrupt handler.
3042H
↳12354		3$SETCAS routine (prompt user to set cassette baud rate)
37DEH
↳14302		Model 1Communication Status Address
37DFH
↳14303		Model 1Communication Data Address
37E0H
↳14304		Model 1Interrupt Latch Address
37E1H
↳14305
↳DSEL$		Model 1Disk Drive Select Latch Address.
  • 01H = Drive :0
37E4H
↳14308		Model 1Cassette Select Latch Address
  • 0 = Tape Drive #1
  • 1 = Tape Drive #2
37E8H
↳14312
↳PRTAD$		1/3$PRSTAT: Printer Status Byte a/k/a Line Printer Address. If a parallel line printer is in use, it is mapped to this address. Writing a byte to this address sends it to the printer, while reading this address determines printer status as follows:
  • Bit 7 = 0 if NOT BUSY
  • Bit 6 = 0 if NOT OUT OF PAPER
  • Bit 5 = 1 if DEVICE SELECTED
  • Bit 4 = 1 if NO PRINTER FAULT
  • Bits 0-3 are NOT USED
  • 63 [00111111] = Printer On (i.e., no printer fault, device selected)
  • 143 [10001111] = Printer Off (i.e., printer fault, device not selected, busy)
37E9H
↳14313		1/3$PROUT: Output a Byte to the Printer.
37EAH
↳14314		Model 1Contains the byte from 37E8H (PRTAD)
37EBH
↳14315		Model 1Contains the byte from 37E8H (PRTAD)
37ECH
↳14316
↳FDCAD$		Model 1Floppy Disk Controller COMMAND/STATUS. This location is tested during the power-up sequence to determine if a floppy disk controller is online, and if so, the TRS-80 will jump to the disk bootstrap routine (unless the BREAK key is held).
  • 00H or FFH = No disk controller found, TRS-80 will jump to Level II BASIC
  • Bit 1 from this memory location is DIM READY
  • 1BH = Command to SEEK
  • 88H = Command to READ SECTOR
  • D0H = Command to FORCE INTERRUPT
37EDH
↳14317		Model 1DISK TRACK SELECT
37EEH
↳14318
↳FDCAD$+2		Model 1DISK SECTOR SELECT
37EFH
↳14319
↳FDCAD$+3		Model 1Byte read from disk (DISK DATA)
3800H-3840H
↳14336-14400
↳KEYAD$		1/3Keyboard Memory / Address Matrix
3B80H
↳15232		1/3Keyboard Memory / Address Matrix for SHIFT Keys
3C00H-3FFFH
↳15360-16383
↳DSPAD$		1/3$VIDRAM: The beginning of video ram or VIDRAM. It ends at 3FFFH or 16383.
3FFFH
↳16383		3END OF VIDEO MEMORY
4000H
↳16384
↳RST1$		1/3RST 08 (Syntax Check): Compare value pointed to by HL to that immediately following RST instruction.
4000H
↳16384		Model 1Start of Level II BASIC Fixed RAM.
4003H-4005H
↳16387-16389		TDRST 10H (Get Next Character): Jump Vector.
4003H
↳16387		RST 10 Examine next symbol pointed to by HL.
4003HModel 1The next 3 bytes are used to hold the length and address of a string when it is moved to the string area.
4006HModel 1RST 18 vector
4006H
↳16390		RST 18H (Cp HL, DE) Jump Vector.
4006H
↳16390		RST 18 Compare DE and HL.
4009H
↳16393		RST 20 Test the type of current variable.
4009HModel 1RST 20 vector
4009H
↳16393		RST 20H (Get Current Type) Jump Vector.
400CH-400EH
↳16396-16398
↳RST5$		1/3RST 28H (Break Key Vector). By default, it contains C9 00 00 (201 00 00) which is RET in NON-DOS BASIC. Any 3 byte instruction code put here will execute on hitting the BREAK key. On a Model I, to disable the BREAK key, Radio Shack recommends filling 16396 with 23 (17H) which is RLA (which just messes with Register A), and with 201 (C9H) RET to re-enable it. On a Model 3, to disable the BREAK key, Radio Shack recommends filling the area with AF C9 00 (175 and 201) which is XOR A / RET. Other methods include filling the area with C3 9A 0A (195 154 10) which is JP 0A9AH.
400CH
↳RST5$		Model 1RST 28 DOS request processing
400CH
↳16396		RST 28 3 byte BREAK key vector (cass. BASIC & TRSDOS1.3) and normal DOS function call.
400FH
↳16399		RST 30 Reserved for DOS; normally for invoking Debug
400FH
↳RST6$		Model 1Load debug (ld a,xx/RST 28)
400FH
↳16399
↳RST6$		Model 3RST 30H Jump Vector.
4012H-4014H
↳16402-16404
↳RST7$ or INTERP		1/3RST 38H Jump Vector.
4012H
↳RST7$ or INTERP		Model 1RST 38 interrupt service call
4012H
↳16402		RST 38 Maskable interrupt vector.

4015H-401CH - Keyboard Device Control Block

Address
(Hex/Dec/Label)		Model
Code		Description
4015H
↳16405
↳KDCB$		Model 1/3Beginning of Keyboard DCB. One byte device type.
  • Value = 1
4016H
↳16406		Model 3Two byte keyboard driver vector. Model 3 it's 3024H, which JUMPs to 338EH which then processes the keyboard)
4016H-4017H
↳16406-16407		Model IKeyboard Device Control Block. Two byte keyboard driver vector. To Disable The Model I Keyboard:
N1=PEEK(16406)
N2=PEEK(16407)
POKE 16406,154
POKE 16407, 10
To Enable The Model I Keyboard:
POKE 16406,N1
POKE 16407,N2
4015H
↳16405
↳KDCB$		Model IKeyboard DCB+0: This address holds the DCB Type
4016H
↳16406		Model IKeyboard DCB+1: This address holds byte 1 of the 2 byte Driver Address
4016H
↳16406		Two byte keyboard driver vector.
4017H
↳16407		Model IKeyboard DCB+2: This address holds byte 2 of the 2 byte Driver Address
4018H
↳16408		Model IKeyboard DCB+3: This address holds
  • Value = 0
4018H
↳16408		1/3Keyboard DCB: Right Shift Toggle
4019H
↳16409		Model IKeyboard DCB+4: This address holds
  • Value = 0
4019H
↳16409		Caps lock switch
  • Not 0 = Caps only
4019H
↳16409		Model 3Caps Lock Toggle
  • 0 = Off (i.e., upper and lower case)
  • Anything else = ALL CAPS
Note: A DOS driver might take over this function.
401AH
↳16410		Model IKeyboard DCB+5: This address holds
  • Value = 0
401AH
↳16410		Model 3Cursor Blink Count.
401BH
↳16411		Model IKeyboard DCB+6: This address holds K
401BH
↳16411		Model 3Cursor Blink Status.
  • 0 = Off
  • NZ = On
401CH
↳16412		Model IKeyboard DCB+7: This address holds I
401CH
↳16412		1/3Cursor Blink Switch.
  • 0 = Blink
  • Anything else = No blink

401DH-4024H - Video Display Control Block

Address
(Hex/Dec/Label)		Model
Code		Description
401DH-4024H
↳16413-16420
↳DDCB$		1/3Beginning of Video Display Control Block (DCB). DCB is Number 7. Classification is both Input and Output.
401DH
↳16413		Beginning of Video DCB. One byte device type.
  • Value = 7
401EH-401FH
↳16414-16415
↳IX+1, IX+2		1/3Two byte video driver address in LSB / MSB order
401EH
↳16414		Two byte video driver vector.
4020H-4021H
↳16416-16417
↳CURSOR, IX+3, IX+4		1/3Cursor Position On Screen. 2 Bytes in LSB/MSB Order.
4020H
↳16416		Two byte cursor position.
4022H
↳16418
↳IX+5		Model 1Cursor Character:
  • 0 = Cursor Off
  • Not 0 = Cursor Character
4022H
↳16418		Model 3Cursor On/Off Flag:
  • Z = Off
  • NZ = Character Under Cursor
4023H
↳16419		1/3Cursor Character (in ASCII). Defaults to 176. Must be between 32 and 255.
4024H
↳16420		FLAG:
  • 0 = Space compression
  • Not 0 = Special character
4024H
↳16420		3Character Set To Use
  • 0 = Regular
  • 1 = Alternate
4024H
↳16420		Model 3Tape RAM - Video DCB: Tabs/Special Characters Switch
  • Z = Tabs

4025H-402CH - Printer Control Block

Address
(Hex/Dec/Label)		Model
Code		Description
4025H
↳16421
↳PDCB$, IX+0		1/3Beginning of Printer DCB. This location, IX+0, is the DCB Type which is set for 6. Classification = Write Only
4026H-4027H
↳16422-16423
↳IX+1, IX+2		1/3Two byte Print Driver Address (stored in LSB/MSB Order).
4028H
↳16424
↳IX+3		1/3Printer: Maximum Number of Lines which can be Printed per Page plus 1. The default is 67.
  • 0 = Top-of-page
4029H
↳16425
↳IX+4		1/3Printer: Number of lines already printed +1. To reset the counter

POKE 16425,1
402AH
↳16426		Model 1Model 1: Not Used
402AH
↳16426		Model 3Number of characters printed already + 1
402BH
↳16427		Model 3Line printer maximum characters (width) per line less 2. Set at 255 for no maximum.
402CH
↳16428		R
402DH
↳16429
↳SYS1IN		 EXIT: Normal program exit back to DOS. (Disk systems only).
402DH
↳16429
↳SYS1IN		Model 3Tape RAM - Printer DCB: JP 5000H Unused DOS Vector
4030H
↳16432
↳ABORT		Model 1DOS request code for SYS1
4030H
↳16432
↳ABORT		 For all DOSes except TRSDOS, jumping here is for an abnormal return to DOS ready, such as after an unsuccessful program exit.
4030H
↳16432		Model 3Tape RAM - Printer DCB: RST 0
4032H
↳16434		Model 1Write 'DOS ready' message
4033H
↳16435
↳CIO$		Model 1Call device driver ala DOS
4033H
↳16435		Model 3Tape RAM - Printer DCB: XOR A and RET
4036H-403CH
↳16438-16444
↳KYBT$		1/3Keyboard Bit Image (7 Byte Buffer). This is the work area for keyboard input routine. The contents of the keyboard rows are stored here so that when the keyboard routine is called, it can determine whether the key has just been depressed (or is still being held down).
  • 4036H = keyboard row address 3801H: @ABCDEFG keys
  • 4037H = keyboard row address 3802H: HIJKLMNO keys
  • 4038H = keyboard row address 3804H: PQRSTUVW keys
  • 4039H = keyboard row address 3808H: XYZ keys
  • 403AH = keyboard row address 3810H: 01234567 keys
  • 403BH = keyboard row address 3820H: 89:;,-./ keys
  • 403CH = keyboard row address 3840H: Enter, Clear, Break, Up, Down, Left, Right, and Space keys
4036H
↳16438		Keyboard buffer (7 bytes).
403DH
↳16445		Level 2Cassette port and print size flag (bit 3) copy (For Model 3, see 4210H).
  • Bit 3: Select video 32 character mode if set
  • Bit 2: Turn the cassette tape relay on if set
  • Bits 1 and 0: Positive and negative audio pulses to the AUX plug
  • Value 0: Video is in 64 characters per line
  • Value 8: Video is in 32 characters per line
403DH
↳16445
↳CAST$		M1 DOS / Model 3Tape RAM - Interrupt Vector 3 - JP 35FAH. This MAY be the routine to add a task to the interrupt chain.
403DH
↳16445
↳CAST$		M3 DOSUsed primarily by the Disk Operating System, vectors at 403DH, 4040H, and 4043H service interrupt vectors 3, 6, and 7 respectively (under non-disk systems all contain a jump to 35FAH, which in turn contains a "RET" instruction). 4046H is an interrupt vector servicing the clock (interrupt vector 2) and contains a jump to 35A9H in a non-disk system. 4049H is the Non-Maskable Interrupt vector and normally contains a RST 0 instruction. The remainder of this area is unused in non-disk systems.
403DH
↳16445		Cassette port and print size flag (bit 3) copy (For Model 3, see 4210H). L3: location of routine to add task to interrupt chain.
403EH-407FH
↳16446-16511
↳CURDOS		M1Unused in non-Disk systems. Real time clock storage locations are kept here. For the Model 3 this would be 4216H-421CH.
403EH
↳16446
↳CURDOS		Model 1Used by DOS
403EH
↳16446
↳CURDOS		D1OSVER$: Holds the DOS Version Number. Stored in DCB format. Note: on a M3 this is stored in 441FH and on the M4 in 0085H
403EH
↳16446		For Model I DOSPLUS, holds DOS version in DCB format.
403FH
↳16447		Model 1Used by DOS
4040H
↳16448		Model 1System bits
4040H
↳16448		Model I25 ms heartbeat counter.
4040H
↳16448		Model 3Interrupt Vector 6 - JP 35FAH. Vector 6 may be "remove task from interrupt chain".
4040H
↳16448		For L1 & M125 ms heartbeat counter. For L3, used to remove task from interrupt chain.
4041H-4043H
↳16449-16451
↳XTIME		L1, D1, and M1TIME$, time of day: Seconds, Minutes, Hours
4041H
↳16449
↳XTIME		Model 1Seconds
4041H
↳16449		Beginning of Time and Date bytes: seconds, minutes, hours, year, day, month. Ends at 4046H or 16454. L1, D1, and M1
4042H
↳16450		Model 1Minutes
4043H
↳16451		Model 1Hours
4043H
↳16451		Model 3Tape RAM - Interrupt Vector 7 - JP 35FAH
4043H
↳16451		L3Change address of interrupt task.
4044H-4046H
↳16452-16454		L1, D1, and M1DATE$, date: Year, Day, Month. Stored in BCD.
4044H
↳16452		Model 1Year
4044H
↳16452		L1, D1, & M1Contains date in binary format.
4045H
↳16453		Model 1Day
4046H
↳16454		Model 1Month
4046H
↳16454		L3Remove task from interrupt chain.
4046H
↳16454		Model 3Tape RAM - Interrupt Vector 2 - JP 35A9H
4047H
↳16455		Model 1Load address for system utilities 2 bytes, initialized to 5200 by sys0/sys
4047H
↳16455		L1Current day in coded form.
4048H
↳16456		Model 1Current interrupt status word
4049H-404AH
↳16457-16458
↳MEMEND		Model 1DOS MEMORY SIZE. Highest available memory location (On a Model 3 it is stored at 4411H)
4049H
↳16457
↳MEMEND		Model 3Tape RAM - RST 0 NMI Vector (Reset If So)
4049H
↳16457		For the Model 3 disk is non-maskable interrupt vector, for Model I disk is highest available memory location (Model 3 = 4411H)
404BH
↳16459		L1Contains image of interrupt latch.
404CH
↳16460		Model 1Interrupt subroutine mask
404DH-404EH
↳16461-16462		T1Address of interrupt service routine for interrupt bit 0
404DH
↳16461		Model 1Reserved (interrupt bit 0)
404FH-4050H
↳16463-16464		T1Address of interrupt service routine for interrupt bit 1
404FH
↳16463		Model 1Reserved (interrupt bit 1)
4050H-4051H
↳16464-16465		Model IFDC Interrupt Vector
4050H
↳16464		Model 1Stack during IPL
4051H-4052H
↳16465-16466		T1Address of interrupt service routine for interrupt bit 2
4051H
↳16465		Model 1Communications interrupt subroutine
4052H-4053H
↳16466-16467		Model ICommunications Interrupt Vector
4053H-4054H
↳16467-16468		T1Address of interrupt service routine for interrupt bit 3
4055H-4056H
↳16469-16470		T1Address of interrupt service routine for interrupt bit 4
4057H-4058H
↳16471-16472		T1Address of interrupt service routine for interrupt bit 5
4058H
↳16472		Model 1Address of clock interrupt routine
4059H-405AH
↳16473-16474		T1Address of interrupt service routine for interrupt bit 6 (which is the DISK interrupt routine)
405BH-405CH
↳16475-16476		T1Address of interrupt service routine for interrupt bit 7
405EH
↳16478		Model I25 MSec Heartbeat Interrupt
4070H
↳16496		Model 1Start of stack during ROM IPL
407DH
↳16509
↳TSTK$		DOSStack pointer for DOS, set by the ROM bootstrap routine
407EH
↳16510		Model 1Reserved
407FH
↳16511		Model 1Reserved
4080H
↳16512
↳FDIVC or RAMLOW		Model 1Subtraction routine used by division code. Code is moved from 18F7H - 1904H during non-disk IPL or by BASIC UTILITY FOR DISK SYSTEMS
4081H
↳16513
↳FDIVC+1		Model 1/3Used in the single precision division routine (stores the LSB). On power up, this routine is moved from 18F7H-1904H to here.
4084H
↳16516
↳FDIVB		Model 1/3Used in the single precision division routine.
4085H
↳16517
↳FDIVB+1		Model 1/3Used in the single precision division routine (stores the NMSB).
4088H
↳16520
↳FDIVA		Model 1/3Used in the single precision division routine.
4089H
↳16521
↳FDIVA+1		Model 1/3Used in the single precision division routine (stores the MSB).
408BH
↳16523
↳FDIVG		Model 1/3Used in the single precision division routine
408CH
↳16524
↳FDIVG+1		Model 1/3Used in the single precision division routine (stores the High Order).

USR and Random Number Routines

Address
(Hex/Dec/Label)		Model
Code		Description
408EH-408FH
↳16526-16527
↳USRTAB		I/III Tape RAMEntry point to the USR subroutine. If you poke the starting addresses correctly, then X=USR(0) will run that routine. 16526 gets the LSB and 16527 gets the MSB.
408EH
↳16526
↳MAXFIL		T1TRSDOS 2.3 stores the answer to the FILES? Question
408FH
↳16527
↳VARREC		T1TRSDOS 2.3 Flag for whether Variable Files were permitted on Entry into BASIC
4090H
↳16528
↳MULTR		I/IIIRandom number seed
4093H-4098H
↳16531-16536
↳STAINP		Model 1/3Input and output port routines
4096H
↳16534
↳OUTWRD		Model 1/3Tape RAM - Tape RAM: Out Support
4099H
↳16537
↳CHARC		Model 1/3INKEY$ storage. This holds the most recently typed keyboard character, stored in ASCII.
409AH
↳16538
↳ERRFLG		Model 1/3Current Error Code is stored at this address (for BASIC only). It would be returned by the ERR function.
409BH
↳16539
↳LPTPOS		Level 2 / Model 3Number of characters already printed in the current line. This would also make it the printer carriage position. It may be used to simulate a TAB function that works correctly past the 63 or 127 character limit of the BASIC TAB function, as TAB cannot be greater than 63 for an old Model I or 127 for a new Model I or any Model 3.
409CH
↳16540
↳PRTFLG, OUTSEL		Model 1/3This is the device output flag.
  • -1 (or 129) = Cassette Output
  • 0 = Video Output
  • 1 = Printer Output
409DH
↳16541
↳LINLEN		Level 2Maximum number of characters on video display line. Used by PRINT command routine when printing numeric variables or constants so that a number does not overflow the end of a video display line. This location is set to 64 at power-up and is not changed by the BASIC interpreter once set. However, a POKE to this location may be used to prevent the PRINTing of numerics beyond a certain point on a line. Also, if you are operating in 32-character display mode it may be necessary to POKE 16541, 32 to prevent numeric printouts from overflowing the end of the line. The setting of this location does not affect the printout of strings (variables or constants).
409EH
↳16542
↳CLMLST		Model 1Size of print line
409EH
↳16542
↳CLMLST		Model 3The value in this location specifies the maximum number of 16-character print zones on a line (used when items in a PRINT statement are separated by commas). Value stored here is decoded as follows:
  • 0 = One print zone
  • 16 = Two print zones
  • 32 = Three print zones
  • 48 = Four print zones per line
When a comma separator is found in a PRINT statement, BASIC checks the cursor line position byte at 40A6H and if it is greater than or equal to the value stored here, a carriage return is output to the video display driver. This location is set to 48 (four print zones) at power-up and is not changed by the BASIC interpreter once set.
409FH
↳16543		Model 1Reserved
409FH
↳16543		Model 3Tape RAM - Data flag. Will indicate if the parser is in a QUOTED STRING (Bit 0 high), REM (Bit 2 high), or DATA (Bit 1 high).

BASIC Memory Management

Address
(Hex/Dec/Label)		Model
Code		Description
40A0H-40A1H
↳16544-16545
↳STKTOP		Model 1/3String Storage Area: 2 Bytes point to the lowest address available for string storage. This is ALSO the top of free memory. Start of string storage area, set to 50 less than top of memory pointer (at 40B1H) at power-up to provide 50 bytes of string storage area. Changed by use of CLEAR n command (with argument).
40A2H-40A3H
↳16546-16547
↳CURLIN		Model 1/3Holds the Last executed (or current) line number in a BASIC Program in 2 Bytes (LSB/MSB) or FFFFH if in direct mode.
40A4H-40A5H
↳16548-16549
↳TXTTAB		Model 1/3Points to the beginning of the BASIC program in RAM, stored in 2 bytes (LSB/MSB). It is the start of the BASIC program in RAM (referred to sometimes as the PST). Normal values for: (L2)=42E9; (Disk BASIC)=varies with version of DOS/BASIC. TO APPEND:
POKE 16548,PEEK(16633)-2 : POKE 16549,PEEK(16634)
CLOAD
POKE 16548,233 : POKE 16549,66
.
What this does is trick the NEW command, which is called as part of CLOAD, into clearing everything AFTER your current program and then restoring where the beginning of the program is afterwards).
This is NOT a MERGE, it will APPEND, and leave line numbers out of order.
40A6H
↳16550
↳TTYPOS		Model 1/3Holds the current cursor position (column number) on the video display line (as returned by the POS function).
40A7H-40A8H
↳16551-16552
↳BUFPNT		Model 1/3Input Buffer Pointer (in BASIC). The address of the BASIC keyboard buffer. Note: Also used by BASIC while encoding and decoding BASIC lines (as during LIST, etc.)
40A9H
↳16553
↳CASFLG		Model 1/3Used by INPUT command routine, contains zero byte if (and only if) input is from cassette. A bug in the first release of the Model I Level II BASIC ROM required that this location be POKEd with a non-zero value prior to reading program DIM statements. This bug was corrected soon after Level II BASIC was released, so that this POKE is required only for older TRS-80 Model I machines.
40AAH-40ACH
↳16554-16556
↳RNDX		Model 1/3Seed Number 1 for Random Number
40ABH
↳16555
↳RNDX+1		Model 1/3Value from refresh register. When a RANDOM is executed in BASIC, this is the byte that gets changed (it is loaded with current value of Refresh register whenever RANDOM statement is executed).
40ACH
↳16556
↳RNDX+2		Model 1Last random number (2 bytes)
40ADH
↳16557		Model 1/3Unused in non-disk systems.
40AEH
↳16558
↳DIMFLG		Model 1Flag:
  • 0 = Locate named variable
  • -1 = Create entry for named variable
40AEH
↳16558
↳DIMFLG		Model 1/3This flag is used by the BASIC locate or create variable routine. If location contains zero, variable is to be created or located (if already created). If byte is not zero, variable is to be created only and an error exists if the variable is found to be already created. The latter situation exists when an array is being created using the DIM statement.
40AFH
↳16559
↳VALTYP, SAFLAG		Model 1/3Contains the variable type flag for the number sitting in the software accumulator (also known as the Work-Register-Area-1).
  • 2 = Integer
  • 3 = String
  • 4 = Single-precision
  • 8 = Double precision
40B0H
↳16560
↳DORES		Model 1Holds intermediate value during expression evaluation
40B0H
↳16560
↳DORES		Model 1/3Used to flag DIM statements while encoding BASIC lines, and to store operator number during expression evaluation.
40B1H-40B2H
↳16561-16562
↳MEMSIZ, MEMTOP		Model 1/3Top of memory pointer. Last usable location for BASIC. This pointer is set by one of the following: If the user answers Memory Size? question with a value, it will be used. However, if only ENTER is pressed in response to Memory Size?, then on a non-disk system the highest available memory location will be used, but under Disk BASIC the DOS top of memory pointer will be copied into this location. If one is programming in BASIC and attempting to change this pointer by POKEing in new values, a CLEAR n statement (with a mandatory numeric argument) should be used immediately following the POKEs, in order to adjust other system pointers to the new memory size. Also, temporarily changing this pointer will allow a short BASIC program to CLEAR more than 32767 bytes of string space on a 48K system, provided that enough free memory is available (BASIC normally does not permit this).
40B1H
↳16561		Two byte MEMTOP (for BASIC).
40B3H-40B4H
↳16563-16564
↳TEMPPT		Level 2Pointer to the next available location for storage of a three-byte string variable VARPTR in the string VARPTR storage area that begins at 40B5H.
40B5H-40D2H
↳16565-16597
↳TEMPST		Level 2String variable VARPTR storage area. Holds three-byte string descriptors (first byte contains length, second and third bytes contain address of string) for strings currently being used in BASIC string operations (such as "temporary" strings).
40D3H-40D5H
↳16595-16597
↳DSCTMP		 VARPTR storage area for string currently being created by BASIC. (first byte contains length, second and third bytes contain address of string).
40D3H
↳16595		Saves length ASCII representation of binary integer.
40D4H
↳16596		Two byte address. Points to buffer where ASCII decimal representation written.
40D6H-40D7H
↳16598-16599
↳FRETOP		Model 1/3Pointer to next free byte in string storage area. Strings build downward from the top of memory, therefore at power-up (or when a CLEAR command is executed) this pointer will contain the same address as the top of memory pointer (40B1H-40B2H). If a ten byte long string is then created, this pointer will point to the top of memory minus ten, and so on. When there is not enough room left to insert a new string (the difference between this pointer and the one at 40A0H-40A1H is less than the length of a string to be stored), a "garbage collection" is performed, and if that does not free enough string space an Out of String Space error occurs. Under some circumstances, we may be able to manipulate this pointer in order to forestall a "garbage collection" (which may appear to "lock up" the computer for as much as several MINUTES). For example, if we are performing some operation that will create many "temporary" strings (but none that we want to save after a certain point), we could PEEK at the values in these pointer locations and store them in numeric variables. At the completion of our string operation, we could then re-POKE the original pointer values, thus abandoning the unneeded strings without performing a "garbage collection". Under certain circumstances this technique could cut program execution time considerably.
40D6H
↳16598		String pointer. Keeps track within CLEARed area as to where last string data was put.
40D8H-40D9H
↳16600-16601
↳TEMP3		Level 2This pair (two byte) of locations is used as temporary storage location by more than one routine. Uses include program pointer during expression evaluation, pointer to data while processing DIM statement, pointer to end of array while packing strings, and within the PRINT USING routine the byte at 40D8H is used to temporarily store the PRINT USING format flag bits.
40D8H
↳16600
↳TEMP3		Model 1
  • Index of last byte executed in current statement
  • Edit flag during print using
40D8H
↳16600		Two byte location of where BASIC is currently reading program.
40DAH-40DBH
↳16602-16603
↳DATLIN		Level 2Line number of last DATA item read. Line number is saved so that in the event of a syntax error in a DATA statement, the proper error line number will be displayed and the EDIT mode will function on the correct line.
40DCH
↳16604
↳SUBFLG		Model 1FOR command flag:
  • 1 = FOR loop is in progress
  • 0 = No FOR loop in progress
40DCH
↳16604
↳SUBFLG		Level 2If this byte contains 64 a FOR-NEXT loop is being processed, otherwise byte will contain zero. Used to prevent an array variable from being used as the index counter in a FOR-NEXT loop (for example, the statement FOR X(0) = 1 TO 10 will cause a syntax error, because X(0) is an array variable and cannot be used as the counter variable).
40DDH
↳16605
↳BFKLFL		Model 1
  • 0 = During input phase
  • Zero otherwise
40DDH
↳16605
↳BFKLFL		Level 2Flag indicates whether inputting text. Used by RETURN and RESUME NEXT commands.
40DEH
↳16606
↳FLGINP		Model 1Read flag:
  • 0 = READ statement active
  • 1 = INPUT statement active
Also used in print using to hold separator between string and variable
40DEH
↳16606
↳FLGINP		Level 2Used for two different purposes: Flags whether READ or INPUT statement when processing those commands (zero represents INPUT). Also used to store delimiter character during processing of PRINT USING statement.
40DFH-40E0H
↳16607-16608
↳TEMP		Model 1/3Used by several routines, as a pointer to variable receiving new value during evaluation of a LET expression, execution address of BASIC program, etc. Also, after a SYSTEM tape is loaded these locations contain the entry point address of the program (which is used if only a / is typed in response to the next SYSTEM command prompt). Is in LSB, MSB order.
40DFH
↳16607
↳TEMP		Model 1Holds execution address for program loaded with DOS request
40DFH
↳16607		Default entry point for SYSTEM tapes.
40E1H
↳16609
↳AUTFLG		 AUTO command.
  • 0 = AUTO numbering is off
  • Any non-zero entry = Next line number
40E2H-40E3H
↳16610-16611
↳AUTLIN		Level 2Line Number: Current line number for the AUTO command. This number is stored in binary during the input phase.
40E4H
↳16612
↳AUTINC		 AUTO command increment value
40E6H-40E7H
↳16614-16615
↳SAVTXT		Model 1/3Pointer to terminator (end of line 00H byte or ":") of the last executed BASIC statement is at this address.
40E6H
↳16614
↳SAVTXT		Model 1During input: address of code string for current statement. During execution: line number for current statement
40E6H
↳16614		Pointer to terminator (end of line 00H byte or ":") of last executed BASIC statement is at this address.
40E8H-40E9H
↳16616-16617
↳SAVSTK		Model 1/3Pointer to the beginning of the STACK POINTER.
40E8H
↳16616
↳SAVSTK		Model 1During execution: holds stack pointer value when statement execution begins
40E8H
↳16616		Beginning of BASIC's stack.
40EAH-40EBH
↳16618-16619
↳ERRLIN		Model 1/3Line Number: The line number which generated an error. This is used for RESUME. If it is 65535, the error originated in command mode instead of in a program.
40EAH
↳16618
↳ERRLIN		Model 1Line number in which error occurred
40EAH
↳16618		Two byte address. Contains line number with error.
40ECH-40EDH
↳16620-16621
↳DOT		Level 2Stores the current line number. Can also be the Line Number for the EDIT command.
40ECH
↳16620		Two byte address. "." line number.
40EEH-40EFH
↳16622-16623
↳ERRTXT		Level 2Pointer to last byte executed when error occurred. Used by RESUME command.
40EEH
↳16622		Pointer to I/O buffer.
40F0H-40F1H
↳16624-16625
↳ONELIN		Level 2Line Number: ON ERROR location for ON ERROR GOTO. That means it is the line number which the error will jump to.
40F2H
↳16626
↳ONEFLG		 Flag to indicate whether an error has occurred. Set to -1 (FFH) on error, otherwise set to zero (such as after RESUME statement has been executed). POKEing the appropriate values into this location will allow you to do many things that BASIC normally does not permit, such as exiting an error trap without using a RESUME statement, or redefining the error trap (by using an ON ERROR GOTO statement) from within a previously defined error trap.
40F3H-40F4H
↳16627-16628
↳TEMP2		Model 1Address of decimal point in pbuff
40F5H-40F6H
↳16629-16630
↳OLDLIN		Level 2Last line number executed prior to execution of STOP or END statement or termination using the BREAK key.
40F7H-40F8H
↳16631-16632
↳OLDTXT		Level 2Pointer to end of last statement executed (points to the colon or zero byte terminator). Used by CONT command.
40F9H-40FAH
↳16633-16634
↳VARTAB		Level 2Starting address of the simple variables list table. This is also one higher than the last of the three zero bytes marking the end of the BASIC program. Used to determine end of BASIC program when saving the program. Note that by taking the address stored here, subtracting 2, and POKEing the resulting address into the start of BASIC program pointer at 40A4H-40A5H, then loading a program with higher line numbers than the one presently in memory, and finally re-POKEing the original values of 40A4H-40A5H back into those locations, it is possible to append a program to a program already in memory.
40FBH-40FCH
↳16635-16636
↳ARYTAB		Model 1/3Starting address of the ARRAY VARIABLE TABLE (end of simple variables)
40FDH-40FEH
↳16637-16638
↳STREND		Model 1/3Pointer to the END of array variables a/k/a start of free memory pointer in LSB, MSB order
40F0H
↳16624		Pointer to line of BASIC error handling.
40F2H
↳16626		Error flag.
40F5H
↳16629		Current line number.
40F9H
↳16633		End of BASIC program/ start of simple variable list pointer.
40FBH
↳16635		Start of arrays variables pointer.
40FDH
↳16637		End of arrays variables/ start of free memory pointer.
40FFH
↳16639		Two byte address. Current location of BASIC's DATA pointer.
40FFH-4100H
↳16639-16640
↳DATPTR		Model 1/3DATA Pointer (2 Byte Address; LSB, MSB). Points to comma or other terminator at end of last item read - search for next DATA item to be read will begin here. RESTORE changes this pointer to point to one byte prior to beginning of BASIC program. A selective RESTORE to some data item past the first can be accomplished by manipulating this pointer. For example, suppose that at some point in your program you will want to RESTORE to the 51st DATA item. At the start of your program you could insert a line similar to this:
FOR X=1 TO 50 : READ X$ : NEXT
R1=PEEK(16639): R2=PEEK(16640) : RESTORE
Then, whenever you wanted to RESTORE to the 51st DATA item, you would simply execute the following statements:
POKE 16639,R1: POKE 16640,R2
The next READ instruction would then get the 51st DATA item.
4101H-411AH
↳16641-16666
↳DEFTBL		Model 1/3Variable declaration list. There are 26 entries (1 for each letter of the alphabet). The location at 4101H applies to variables starting with the letter A, 4102H applies to variables starting with B, 4103H to variables starting with C and so on up to 411AH, which contains the default type for all variables starting with the letter Z. Each location contains one of the following values:
  • 2 = Integer
  • 3 = String
  • 4 = Single precision
  • 8 = Double precision
When a variable name is used in a BASIC program and does not have a specific type declaration character (%, $, !, or #) following, its type defaults to the type specified in this table. All defaults are set to single-precision when a program is RUN, and may be changed through use of the DEFINT, DEFSTR, DEFSNG, or DEFDBL statements.
4101H
↳16641		Beginning of variable type table.
411AH
↳16666		End of variable type table.
411BH
↳16667		Trace flag.
411BH
↳16667
↳TRCFLG		Model 1TRON Trace flag
  • 0 = Off (TROFF)
  • Non-zero = On
411CH
↳16668
↳DFACLO-1		Model 1Temporary storage used by numeric routines when unpacking a floating point number. Usually it holds the last byte shifted out of the LSB position
411DH-4124H
↳16669-16676
↳DFACLO		Model 1/3Software Accumulator (SA) - 2 Bytes
411DH
↳16669
↳DFACLO		Model 1Work-Register-Area-1 - LSB of double precision value
411DH
↳16669		First byte of SA.
4124H
↳16676		Last byte of SA.
4127H
↳16679		First byte of SA1.
412EH
↳16686		Last byte of SA1.
4120H
↳16672
↳FACLO-1		Model 1Work-Register-Area-1 - double precision value
4121H-4122H
↳16673-16674
↳FACLO		Model 1/3Single precision number storage area for single precision math routines - 2 Bytes (4121H=MSB)
4123H-4124H
↳16675-16676
↳FAC-1		Model 3Single precision number storage area for single precision math routines - 2 Bytes (4123H=MSB)
4123H
↳16675
↳FAC-1		Model 1Work-Register-Area-1 - MSB for single precision
4124H
↳16676
↳FAC		Model 1Work-Register-Area-1 - exponent for single precision
4125H
↳16677
↳FAC+1		Model 1Sign of result during math & arithmetic operations
4126H
↳16678
↳ARGLO-1		Model 1Bit bucket used during double precision addition
4127H-412EH
↳16679-16686
↳ARGLO a/k/a ARG-7		Model 1/3Alternate Software Accumulator (SA1 or REG2) - 2 Bytes
4127H
↳16679
↳ARGLO		Model 1Work-Register-Area-2 - LSB
4128H
↳16680		Model 1Work-Register-Area-2
4129H
↳16681		Model 1Work-Register-Area-2
412AH
↳16682		Model 1Work-Register-Area-2
412CH
↳16684		Model 1Work-Register-Area-2
412DH
↳16685
↳ARG-1		Model 1Work-Register-Area-2 - MSB
412EH
↳16686
↳ARG		Model 1Alternate Software Accumulator - exponent
412FH
↳16687
↳FBUFFR		Level 2 (Non-Disk)Unused.
4130H-4149H
↳16688-16713
↳FBUFFR+1		Level 2Multipurpose Storage/Work Area. Buffer used to store result of conversion of numbers to displayable ASCII characters. When positive integers (BASIC line numbers, etc.) are converted, the area from 4130H to 4136H is used, and the string is stored right justified with leading spaces in locations 4130H to 4135H (4130H always contains a space character), while 4136H always contains a zero byte to terminate the string. Other routines (such as PRINT USING) may use more of this area.
414AH
↳16714
↳FBUFFR+27		Model 3Tape RAM - Workspace For Double Precision Division (8 Bytes). Basically, a temporary ACCUM sometimes used by arithmetic routines (such as to hold divisor used by double precision division routine).
414FH
↳16719
↳FMLTT1		Model 1Temporary Storage
4150H
↳16720
↳FMLTT2		Model 1Temporary Storage
4151H
↳16721
↳FBUFFR+34		Model 1End of temporary area. Locations 4152H through 41E2H contain DOS exits and disk BASIC exits. On non-disk systems these locations are initialized to RETurns (RET'S) while on disk based systems they will be initialized as shown.

4152H-41A6H - DISK BASIC entry points

Address
(Hex/Dec/Label)		Model
Code		Description
4152H
↳16722
↳ERCALL		Model 1/3Disk BASIC Vector: CVI vector (3 byte jump command to handler)
4155H
↳16725		Model 1/3Disk BASIC Vector: FN vector (3 byte jump command to handler)
4158H
↳16728		Model 1/3Disk BASIC Vector: CVS vector (3 byte jump command to handler)
415BH
↳16731		Model 1/3Disk BASIC Vector: DEF vector (3 byte jump command to handler)
415EH
↳16734		Model 1/3Disk BASIC Vector: CVD vector (3 byte jump command to handler)
415FH
↳16735		Model 1Work-Register-Area-1 - double precision value
4160H
↳16736		Model 1Disk basic exit (MKS$)
4161H
↳16737		Model 1/3Disk BASIC Vector: EOF vector (3 byte jump command to handler)
4164H
↳16740		Model 1/3Disk BASIC Vector: LOC vector (3 byte jump command to handler)
4167H
↳16743		Model 1/3Disk BASIC Vector: LOF vector (3 byte jump command to handler)
416AH
↳16746		Model 3Disk BASIC Vector: MKI$ vector (3 byte jump command to handler)
416DH
↳16749		Model 3Disk BASIC Vector: MKS$ vector (3 byte jump command to handler)
4170H
↳16752		Model 1/3Disk BASIC Vector: MKD$ vector (3 byte jump command to handler)
4173H
↳16755		Model 1/3Disk BASIC Vector: CMD vector (3 byte jump command to handler)
4176H
↳16758		Model 1/3Disk BASIC Vector: TIMES$ vector (3 byte jump command to handler)
4179H
↳16761		Model 1/3Disk BASIC Vector: OPEN vector (3 byte jump command to handler)
417CH
↳16764		Model 1/3Disk BASIC Vector: FIELD vector (3 byte jump command to handler)
417FH
↳16767		Model 1/3Disk BASIC Vector: GET vector (3 byte jump command to handler)
4182H
↳16770		Model 1/3Disk BASIC Vector: PUT vector (3 byte jump command to handler)
4185H
↳16773		Model 1/3Disk BASIC Vector: CLOSE vector (3 byte jump command to handler)
4188H
↳16776		Model 1/3Disk BASIC Vector: LOAD vector (3 byte jump command to handler)
418BH
↳16779		Model 1/3Disk BASIC Vector: MERGE vector (3 byte jump command to handler)
418EH
↳16782		Model 1/3Disk BASIC Vector: NAME vector (3 byte jump command to handler)
4191H
↳16785		Model 1/3Disk BASIC Vector: KILL vector (3 byte jump command to handler)
4194H
↳16788		Model 1/3Disk BASIC Vector: & vector (3 byte jump command to handler)
4197H
↳16791		Model 1/3Disk BASIC Vector: LSET vector (3 byte jump command to handler)
419AH
↳16794		Model 1/3Disk BASIC Vector: RSET vector (3 byte jump command to handler)
419DH
↳16797		Model 1/3Disk BASIC Vector: INSTR vector (3 byte jump command to handler)
41A0H
↳16800		Model 1/3Disk BASIC Vector: SAVE vector (3 byte jump command to handler)
41A3H
↳16803		Model 1/3Disk BASIC Vector: LINE vector (3 byte jump command to handler)
41A6H
↳16806
↳RETCNT		 ERROR Error processing jumps to this three byte vector. In cassette BASIC it contains RET instruction, in Disk BASIC, contains a jump (through RST) to display long error messages.
41A6H
↳16806		 ERROR Error processing jumps to this 3-byte vector. In cassette BASIC it contains RET instruction; in Disk BASIC, contains a jump (through RST) to long error message
41A6H
↳16806
↳RETCNT		Model 1Disk basic exit (USR) the following addresses are the DOS exit addresses.
41A9H
↳16809		 USR 3 byte vector.
41A9H
↳16809		Model 1/3DOS Link For USR N (3 byte vector) which is used to expand function to provide up to ten USR calls.
If you want to knock out all uses of USR in a BASIC program, POKE 16809,215:POKE 16810,216:POKE 16811,43:POKE 16812,201 to load this with RST 10, RET C, DEC HL, RET. To be super sure, also then POKE 16527,65:POKE 16526,171 which will point to the RET.
41ACH
↳16812		 Ready prompt
41ACH
↳16812		Model 1DOS exit from 1A1C
41ACH
↳16812		 Ready prompt
41ACH
↳16812		Model 3Tape RAM - DOS Links: Link For Ready
41AFH
↳16815		 Called from 0368H to input line from keyboard to I/O buffer.
41AFH
↳16815		Model 1DOS exit from 0368
41AFH
↳16815		 Called from 0368H to input line from keyboard to I/O buffer.
Inputs a line from the keyboard into the I/O buffer (zeroes INKEY$ buffer and video tab position indicator prior to call).
41AFH
↳16815		Model 3Tape RAM - DOS Links: Link For INKEY$
41B2H
↳16818		 Called from 1AA1H immediately after BASIC line is tokenized. HL points to tokenized line.
41B2H
↳16818		Model 1DOS exit from ROM address 1AA1
41B2H
↳16818		Model 3Called from 1AA1H immediately after BASIC line is tokenized. HL points to tokenized line.
41B5H
↳16821		 Called from 1AECH immediately after BASIC's table of program lines are updated. After call to 41B5H, BASIC calls CLEAR routine at 1B5DH then calls this DOS exit from 1AF2H
41B5H
↳16821		Model 1DOS exit from ROM address 1AEC
41B5H
↳16821		Model 3Called from 1AECH immediately after BASIC's table of program lines are updated (insertion or replacement of a BASIC line). After call to 41B5H, BASIC calls CLEAR routine at 1B5DH then calls this DOS exit from 1AF2H
41B8H
↳16824		Model 1DOS exit from ROM address 1AF2
41B8H
↳16824		Model 3Called at 1AF2H, after above call followed by call to 1B5DH (CLEAR command, leaves HL pointing to start of BASIC program -1).
41BBH
↳16827		Model 1DOS exit from ROM address 1B8C
41BBH
↳16827		Model 3Called from 1B8CH and 1DB0H during NEW and END processing to allow Disk Basic to close any open files.
41BBH
↳16827		 Called from 1B8CH and 1DB0H during NEW and END processing to allow Disk Basic to close open files.
41BEH
↳16830		 PRINT# processing called from 2174H
41BEH-41C0H
↳16830-16832		Level 2(L2 only) Jumps here on RESET button hit. You can put your own 3 byte instruction here to jump to your own routine.
41BEH
↳16830		Model 1DOS exit from ROM address 2174
41BEH
↳16830		Model 3Called at 2174H, at termination of PRINT statement (used to terminate output to disk using PRINT# statement).
41C1H
↳16833		 Byte output to any device. Called from 032CH so output to disk can be handled as to other devices.
41C1H
↳16833		Model 1DOS exit from ROM address 032C
41C1H
↳16833		Model 3Byte output to any device. Called from 032CH so output to disk can be handled as to other devices.
41C4H
↳16836		 ROM KB scan (0358H) calls this exit. BASIC processes INKEY$ here and also after each command when system searches for BREAK or SHIFT+@.
41C4H
↳16836		Model 1DOS exit from ROM address 0358
41C4H
↳16836		Model 3ROM KB scan (0358H) calls this exit. BASIC processes INKEY$ here and also after each command when system searches for BREAK or SHIFT+@.
41C7H
↳16839		 Called from 1EA6H when RUN is followed by filename or line number
41C7H
↳16839		Model 1DOS exit from ROM address 1EA6
41C7H
↳16839		Model 3Called from 1EA6H when RUN is followed by filename or line number
41CAH
↳16842		 Related to 41BEH above. Called at Beginning of print processing from 206FH to check for possible disk output.
41CAH
↳16842		Model 1DOS exit from ROM address 206F
41CAH
↳16842		Model 3Related to 41BEH above. Called at Beginning of print processing from 206FH to check for possible disk output (i.e., PRINT# ).
41CDH
↳16845		 Called from 20C6H. Call made during print processing after number is in ASCII and just before printing. Could be used for Hex and Binary printing.
41CDH
↳16845		Model 1DOS exit from ROM address 2103
41CDH
↳16845		Model 3Called from 20C6H. Call is made during print processing after number is in ASCII and just before printing. Could be used for Hex and Binary printing.
41D0H
↳16848		 Called from 2103H (from PRINT routine after code that send CR.) Could be used for screen wrap-around.
41D0H
↳16848		Model 1DOS exit from ROM address 2103
41D0H
↳16848		Model 3Called from 2103H (from PRINT routine after code that send CR.) Could be used for screen wrap-around.
41D3H
↳16851		 Called from 2108H and 2141H. First is for printing with comma tabs, second is for printing with TAB statement. Could be used to increase length of original tabs from 63 or 127 up to 255.
41D3H
↳16851		Model 1DOS exit from ROM address 2108
41D3H
↳16851		Model 3Called at 2108H (from PRINT command when a comma is used to separate items to be printed) and at 2141H (from PRINT command routine when the TAB function is used, after the TAB argument has been evaluated and placed in the E register. It is worth noting that the original argument (if within the range 0-255) is still stored as an integer in ACCUM, with the NTF set to 2, indicating an integer (when this vector is called from the comma separator routine the NTF will normally be set to 3, indicating a string).
41D6H
↳16854		Model 1DOS exit from ROM address 219E
41D6H
↳16854		Model 3INPUT# processing. Called from 219EH to check for INPUT# command and to provide input from disk.
41D6H
↳16854		 INPUT# processing. Called from 219EH to check for INPUT# command and to provide input from disk.
41D9H
↳16857		 Left side of MID$ processing. Only DOS exit BASIC jumps to instead of calls. Used to allow MID$ on left side of equals sign.
41D9H
↳16857		Model 3The Disk BASIC routine that permits MID$ to be on the left side of an "=". FTI this is the only DOS exit BASIC jumps to instead of calls.
41DCH
↳16860		 Variables assignment. During processing of READ & INPUT statements, after computer receives value and before assigned to variable, BASIC calls this exit from 222DH.
41DCH
↳16860		Model 1DOS exit from ROM address 222D
41DCH
↳16860		Model 3Called at 222DH. Part of READ / INPUT command routine, called just prior to assigning data that has been read or INPUT to variable. After computer receives value and before assigned to variable, BASIC calls this exit from 222DH.
41DFH
↳16863		 Called twice from BASIC: From 2278H after BASIC assigns input value to variable and just before BASIC searches for extra data that will generate "Extra ignored" message, and from 2B44H from the midst of list processing. Could be used to alter list command.
41DFH
↳16863		Model 1DOS exit from ROM address 2278
41DFH
↳16863		 Called twice from BASIC: From 2278H after BASIC assigns input value to variable and just before BASIC searches for extra data that will generate "Extra ignored" message, and from 2B44H from the midst of list processing. Could be used to alter list command.
41E2H
↳16866		 SYSTEM command processing. Called from 02B2 just before "*?" prompt. A system tape will automatically start if a jump to its starting address is placed here. Keep in mind this is a 3 byte location. The first byte should be C3H which is the code for "JP" and should be followed by the starting address of your program.
41E2H
↳16866		Model 1DOS exit from ROM address 0282
41E2H
↳16866		Model 3SYSTEM command processing. Called from 02B2 just before "*?" prompt. A system tape will automatically start if a jump to its starting address is placed here. Keep in mind this is a 3 byte location. The first byte should be C3H which is the code for "JP" and should be followed by the starting address of your program.
41E5H-41FCH
↳16869-16892
↳BUFINI-3		Model 3 ONLYDevice Control Blocks for RS-232-C Input, Output, and Initialization.
41E5H-42E8H
↳16869-17128
↳BUFINI-3		Model I ONLY Addresses 41E5H-41E7H are initialized by ROM code at 0080H-0089H to contain the bytes 3AH, 0, and 2CH (a colon, zero byte, and comma). The BASIC input/output buffer (also used while encoding and decoding BASIC lines) begins one byte higher (41E8H) and is defined by a continuation of the above mentioned ROM code (008AH - 008DH), which initializes the buffer pointer at 40A7H-40A8H. The buffer is exactly 256 (100H) bytes long, and is immediately followed by a byte that is always zero, and marks the end of reserved RAM (42E8H).
41E5H
↳16869
↳BUFINI-3		Model 3Tape RAM - RS-232 Input DCB: Type = 1 = Read Only
41E6H-41E7H
↳16870-16871		Model 3Tape RAM - RS-232 Input DCB: 2 Byte Driver Address (301EH)
41E8H
↳16872		 $RSRCV input buffer (1 byte)
41E8H
↳16872
↳BUFINI		Model 1/3Tape RAM - RS-232 Input DCB: RS-232 Input Buffer (1 Character)
41E9H
↳16873		Model 3Tape RAM - RS-232 Input DCB: Bit 2 = Driver On/off Bit 1 = Wait/no Wait
41EAH
↳16874		Model 3This sits in the RS-232 INPUT DCB, but I have no idea what it does and what uses it
41EBH, 41ECH, and 41F3H
↳16875, 16876 and 16883		4 in 3 ModeASCII character that will be returned when F1, F2, or F3 key is depressed. Normally set to 60H ( SHIFT+@) during BASIC initialization, but the character stored at this location may be changed, so that any desired character may be returned when the appropriate function key is pressed.
41EBH-41ECH
↳16875-16876		Model 3The "RI" device name.
41EDH
↳16877		Model 3Tape RAM - RS-232 Output DCB: Type = 2 = Write Only
41EEH
↳16878		Model 3Tape RAM - RS-232 Output DCB: 2 Byte Driver Address (3021H)
41F0H
↳16880
↳RSTX		Model 1/3RS-232 Output DCB: Output Buffer (1 Character)
41F0H
↳16880		 $RSTX output buffer (1 byte)
41F1H
↳16881		Model 3Tape RAM - RS-232 Output DCB: Bit 2 = Driver On/off Bit 1 = Wait/no Wait
41F2H
↳16882		Model 3This sits in the RS-232 OUTPUT DCB, but I have no idea what it does and what uses it
41F3H-41F4H
↳16883-16884		Model 3The "RO" device name.
41F4H
↳16884		Model 1/3Value 103
 – 1st of 2 to Change LINE keyword to act as LPRINT
41F4H
↳16884		4 in 3 ModeStorage location for keyboard scan routine. The contents of the keyboard "row" at 3880H is stored here.
Bit 0: LEFT SHIFT
Bit 1: RIGHT SHIFT:
Bit 2: CONTROL
Bit 3: Caps
Bit 4: F1
Bit 4: F1
Bit 5: F2
Bit 6: F3
Bit 7: Unused
41F5H
↳16885		Model 1/3Value 32
2nd of 2 to Change LINE keyword to act as LPRINT
41F5H
↳16885		Model 3Tape RAM - RS-232 Initialization DCB: Type = 2 = Write Only
41F6H-41F7H
↳16886-16887		Model 3Tape RAM - RS-232 Initialization DCB: 2 Byte Driver Address (301BH)
41F8H
↳16888
↳BUFINI+20		Model 1/3, Model 3$RSINIT: Baud Rate Code. Bits 7-4=Transmit Baud, Bits 3-0=Received Baud. These two tend to be the same so they range from 00H-EEH for 50 (00H), 75 (11H), 110 (22H), 134.5 (33H), 150 (44H), 300 (55H), 600 (66H), 1200 (77H), 1800 (88H), 2000 (99H), 2400 (AAH), 3600 (BBH), 4800 (CCH), 7200 (DDH), 9600 (EEH)
41F8H
↳16888		 $RSINIT baud rate code. TX code = most sig. nibble, RCV code = least significant nibble.
41F9H
↳16889		Model 1/3Tape RAM - RS-232 Initialization DCB - $RSINIT: Parity/Word Length/Stop-Bit code. Default is 108.
41F9H
↳16889		Model 3RS-232 Configuration Byte.
Bit 0=Data Transmit Ready (always 0), Bit 1=Ready to Send (always 0), Bit 2=Transmit Enable/Disable (1=Enable, 0=Disable), Bit 3=Parity Enable (1=Parity Enable, 0=No Parity), Bit 4=Stop Bits (1=2 Stop Bits, 0=1 Stop Bit), Bits 6-5=Word Length (00=5, 01=6, 10=7, 11=8), Bit 7=Parity Odd/Even (1=Odd, 0=Even)
41F9H
↳16889		 $RSINIT parity/word/length stop-bit code
41FAH
↳16890		Model 1/3$RSINIT: Wait Switch
  • 0 = wait
  • Not 0 = no wait
41FAH
↳16890		 $RSINIT wait switch (0 = wait, Not 0 = no wait)
41FBH-41FCH
↳16891-16892		Model 3The "RN" device name.
41FDH
↳16893		Model 3 OnlyUsed by repeating key routine. Saves LSB of keyboard buffer pointer (buffer at 4036H-403CH) when key is found depressed.
41FEH
↳16894		Model 3 OnlyUsed by repeating key routine. Saves contents of current keyboard "row" when key is found depressed.
41FFH-4200H
↳16895-16896		Model 3 ONLYUsed by repeating key routine. Holds maximum repeat delay count (1500 decimal or 5DCH for first repeat delay, 150 decimal or 96H for subsequent repeats of same character).
4200H-51FFH
↳16896-20991
↳MEM$		Level 2TRSDOS v2.3
  • 4200H-42FFH - This is where the LEVEL II ROM dumps Drive 0, Track 0, Sector 0. The ROM routine which does this is located at 06B6H-06CBH.
  • 4D00H-4DFFH - This is where BOOT/SYS loads SYS0/SYS.
  • 4E00H, TRSDOS v2.3 disables interrupts, selects Interrupt Mode 1, and sets the utility load address to 5200H.
  • 4E0FH-4E1BH - Calculate how much RAM is present and puts that in 4049H.
  • 4E20H-4E55H - Initialize the device address table (43B8-43BF) and the device mnemonic table (43C0-43CC). These tables are used by the DEVICE command.
4200H-42FFH
↳16896-17151		Model 1System Sector Buffer Area
4201H-4202H
↳16897-16898		Model 3 ONLYUsed by repeating key routine. Holds current repeat delay count, which is compared with value at 41FFH-4200H to determine if it is time to repeat the character.
4203H-4205H
↳16899-16901		Model 3 ONLYThree byte BREAK key vector used when BREAK is pressed during cassette tape or RS-232-C operations. Initialized to contain a jump to 022EH, which in turn contains EI and JP 1A19H instructions.
4206H-4208H
↳16902-16904		Model 3 ONLYThree byte vector services interrupt # 4. Under non-disk systems contains a jump to 35FAH, which in turn contains a "RET" instruction.
4209H
↳16905		L3Checks for drive and mounted disk.
4209H-420BH
↳16905-16907		Model 3 ONLYThree byte vector services interrupt # 5. Under non-disk systems contains a jump to 35FAH, which in turn contains a "RET" instruction.
420CH-420DH
↳16908-16909		Model 3 ONLYPointer to "write byte to cassette" routine. Initialized by "write cassette leader" routine, normally contains address of either 500 baud (3241H) or 1500 baud (32BAH) byte output routine.
420EH-420FH
↳16910-16911		Model 3 ONLYPointer to "read byte from cassette" routine. Initialized by "read cassette leader" routine, normally contains address of either 500 baud (3203H) or 1500 baud (32CAH) byte input routine.
4210H
↳16912		Model 3 ONLYA flag byte used by the BASIC interpreter, this location contains the CURRENT PORT 0ECH OUTPUT BITS, which are organized as follows:
BIT 6: Enables fast clock speed if set on Model 4 ONLY
BIT 5: Disables video wait states if set (not used on Model 4).
BIT 4: Enables I/O bus if set
BIT 3: Japanese Kana character set used as "special" characters if set
BIT 2: Select video 32 character mode if set
BIT 1: Turns on cassette tape relay if set
BIT 0: Enables clock display on video if set
Programmers that attempt to output to port ECH should be aware that at various points in the BASIC interpreter ( such as when returning to BASIC "READY", doing tape I/O, etc.) some or all of the bits stored here may be output to port ECH, thereby canceling the previous status of port ECH. Also, it must once again be noted that in all current editions of the Model 3 ROM, an error exists in that the test for double-width characters at 0348H has not been changed to test the flag at 4210H rather than the flag at 403DH. This can cause serious problems when attempting to make use of the 32-character mode on the Models III and 4.
4210H
↳16912		Model 3 ONLYPort ECH Bit Mask:
  • Bit 1: Cass motor [0 = on, 1 = off]
  • Bit 2: Double width [0 = normal, 1 = double]
  • Bit 3: Alt. char. [0 = disable, 1 = enable]
  • Bit 4: I/O bus [0 = disable, 1 = enable] - Model 4 ONLY
  • Bit 5: Video waits [0 = disable, 1 = enable] - Model 4 ONLY
  • Bit 6: CPU clock speed [0 = 2 MHz, 1 = 4 MHz] - Model 4 ONLY
  • Bit 7: not used
4211H
↳16913		Model 3 ONLYCassette Info: Cassette Baud Rate Select (0 = 500 baud, Not 0 = 1500 baud)
4212H
↳16914		Model 3 ONLYCassette Info: Cassette Blinker Counter.
Each time a byte is read from tape, this counter is incremented and ANDed with 5FH. If the result is zero, the status of the asterisk in the upper right corner of the video display is reversed (turned on if it was off, or off if it was on).
4213H
↳16915		Model 3 ONLYCassette Info: Default Interrupt Vector Setting.
This byte is output to port E0H (the maskable interrupt latch) whenever the "turn off cassette" routine is executed.
4214H
↳16916		Model 3 ONLYVideo display scroll protect: # Video Lines To Protect (0-7). Default is 0. Only the lowest three bits are used (byte is ANDed with 7 to determine number of protected lines).
4214H
↳16916		 Video display scroll protect (range = 0 - 7)
4215H
↳16917		Model 3 ONLYUnused In non-Disk System
4216H
↳16918		Model 3 ONLYTape RAM - Clock Data: Heartbeat Counter
4217H
↳16919		Model 3 ONLYTape RAM - Clock Data: Seconds (Value: 00-59). You can POKE to change.
4217H
↳16919		 Model 3 time. Contains time in binary format.
4218H
↳16920		Model 3 ONLYTape RAM - Clock Data: Minutes (Value: 00-59). You can POKE to change.
4219H
↳16921		Model 3 ONLYTape RAM - Clock Data: Hours (Value: 00-23). You can POKE to change.
421AH
↳16922		Model 3 ONLYTape RAM - Clock Data: Year (Value: 00-99). You can POKE to change.
421AH
↳16922		 Model 3 date. Contains date in binary format.
421BH
↳16923		Model 3 ONLYTape RAM - Clock Data: Day (Value: 01-31). You can POKE to change.
421CH
↳16924		Model 3 ONLYTape RAM - Clock Data: Month (Value: 01-12). You can POKE to change.
421DH
↳16925		Model 3Tape RAM - I/O Router DCB: Type = 2 = Write Only
421EH
↳16926		Model 3Tape RAM - I/O Router DCB: Driver Address (3739H)
4220H-4221H
↳16928-16929		Model 1/3$ROUTE: Destination Device Name for ROUTE Routine. 2 Bytes
4220H
↳16928		 $ROUTE destination device (two bytes)
4222H-4223H
↳16930-16931		Model 3Tape RAM - I/O Router DCB: Source Device Name. 2 Bytes.
4222H
↳16930		 $ROUTE source device (two bytes)
4224H
↳16932		Model 3 ONLYControl key flag used by keyboard driver routine. Contains 1FH if control key sequence (LEFT SHIFT and DOWN-ARROW keys was pressed), else contains FFH. Can be tested to determine how certain control codes were produced ( for example, whether a carriage return character was produced by pressing the ENTER key, or through the use of the Control-M sequence).
4225H
↳16933		Model 3 CassetteUndefined, except that the SYSTEM command places its Stack Pointer within this area, at 4288H.
4225H
↳16933		Model 3, L3, Model 3DOS command buffer.
4271H
↳17009		Model 3 TRSDOSASCII-coded drive number "0," "1," "2," or "3" for use with the Display Short Directory routine.
4288H
↳17032		L333.33 ms heartbeat counter.
4288H
↳17032
↳BUFINI+160		Model 3 CassettePresumed starting location for a SYSTEM command.
428AH
↳17034		L3Send message to Job Log and CRT.
428DH
↳17037		Model 3, Model 3Find drive and file number for open file. For L3, send message to Job Log.
4290H
↳17040		Model 3, L3, Model 3Copy directory to RAM buffer.
4293H
↳17043		 Get file name from directory.
4296H
↳17046		L3Execute DOS command and return to DOS ready.
4299H
↳17049		Model 3Do DOS command and return to DOS ready. L3: returns to caller is @EXIT and @ABORT vectors change to jump to return address.
429CH
↳17052		Model 3Do DOS command and return to caller.
42ADH
↳17069		Model 3Contains address of break key routine.
42B3H
↳17075		Model 3Which disk drive is the master drive number.
42B4H
↳17076		Model 3This is the CLEAR RAM flag.
42E5H-43E8H
↳17125-17384		Model 3 ONLY Addresses 42E5H-42E7H are initialized by ROM code at 0080H-0089H to contain the bytes 3AH, 0, and 2CH (a colon, zero byte, and comma). The BASIC input/output buffer (also used while encoding and decoding BASIC lines) begins one byte higher (42E8H) and is defined by a continuation of the above mentioned ROM code (008AH - 008DH), which initializes the buffer pointer at 40A7H-40A8H. The buffer is exactly 256 (100H) bytes long, and is immediately followed by a byte that is always zero, and marks the end of reserved RAM (43E8H).
42E8H
↳17128
↳ENBINI, TSTACK		Model 1Always Zero
42E9H
↳17129		Model 1/3 (Non-DOS)Start of user RAM for program storage. Fills down from this memory address in the following order: Program Text, Simple Variables, Arrays, String Variable Names and Overhead, Free Memory.
42FFH
↳17151		Model 3Protection Override Flag (If Bit 0 is set, password checking is disabled).
4300H
↳17152		Model 1Used by TRSDOS 2.3 to store the last track addressed on Drive 0
4301H
↳17153		Model 1Used by TRSDOS 2.3 to store the last track addressed on Drive 1
4302H
↳17154		Model 1Used by TRSDOS 2.3 to store the last track addressed on Drive 2
4303H
↳17155		Model 1Used by TRSDOS 2.3 to store the last track addressed on Drive 3
4304H
↳17156		Model 1Used by TRSDOS 2.3 to store the directory Track for Drive 0
4305H
↳17157		Model 1Used by TRSDOS 2.3 to store the directory Track for Drive 1
4306H
↳17158		Model 1Used by TRSDOS 2.3 to store the directory Track for Drive 2
4307H
↳17159		Model 1Used by TRSDOS 2.3 to store the directory Track for Drive 3
4308H
↳17160		Model 1Used by TRSDOS 2.3 to store the last disk drive accessed
4309H
↳17161		Model 1Used by TRSDOS 2.3 to store the last unit mask for the last drive selected
430AH-430CH
↳17162-17164		Model 1Used by TRSDOS 2.3 to store the DCB/Buffer address, current operation
430CH-430DH
↳17164-17165		Model 1Used by TRSDOS 2.3 to store the DCB address for the current operation
430EH
↳17166		Model 1Used by TRSDOS 2.3 to store the last Overlay Load Request
430FH
↳17167
↳XMODE		Model 1Used by TRSDOS 2.3 to track certain system conditions.
  • If Bit 4 is set, then SYS6/SYS is loaded in RAM (and can be called by RST 28H).
  • If Bit 5 is set, then CHAINING is in effect.
  • If Bit 7 is set, then DEBUG was set to active.
4312H
↳17170		ND1, Model 1Break Key Vector
  • 195=Off
  • 201=On
4313H
↳17171
↳XFCN		ND1, Model 1This is in the middle of a JP nnnn command and the Jump Vector will be put here
4315H
↳17173
↳XPROT		ND1, Model 1, Model 1This is an OPCODE and can be swapped to RET or JUMP based on a CMD"S" or CMD"A" command
4318H
↳17176		Model 1, L1, Model 1DOS command buffer. Contains the last DOS command entered. Maximum of 64 Characters.
4396H
↳17302		L1Read directory into memory.
43E9H-
↳17385-		Model 3RAM - BASIC PROGRAM IN A CASSETTE SYSTEM
4400H
↳17408		 CMD is a routine that accepts a new command to be evaluated. To Use:
CALL 4400H
4400H
↳17408		L1, Model 1/3, N1, N3, Model 1/3Same as 402D: return to DOS ready.
4402H
↳17410		 Send text to file or device.
4405H
↳17413		 CMNDI is the entry into the command interpreter. To use, the following 3 lines are necessary only if this is called at the end of BASIC program.
LD HL,402D ;DOS return address
LD (41FAH),HL
LD SP,41FAH ;reset stack pointer for DOS
Your ASCII DOS command should be in the command buffer terminated by a carriage return. To Use:
LD HL,4318H ;DOS command buffer
JP 4405H ;if from BASIC
CALL 4405H ;else this way
4405H
↳17413		L1, Model 1/3, N1, N3, Model 1/3Do DOS command and return to DOS ready.
4409H
↳17417		 Display error message on CRT.
440DH
↳17421		L1, L3, Model 1/3, N1, N3, Model 1/3Enter Debug.
4410H
↳17424		L1, Model 1, N1, Model 1Add task to interrupt chain.
4411H-4412H
↳17425-17426		Model 3MEMORY SIZE Model 3 DISK BASIC
4411H
↳17425		 Address of highest available memory location (Model 3 disk only - Model 1 disk = 4049H)
4413H
↳17427		L1, Model 1, N1, N3, Model 1Remove task from interrupt chain. For Model 3, add task to interrupt chain.
4413H
↳17427		Model 3Highest Disk Drive attached to the system.
4414H
↳17428
↳TSTACK+300		Model 3System OVERLAY number Currently in RAM.
4415H
↳17429		Model 3Second copy of high memory address. Copied to 4411H in case of I/O error during DO processing.
4416H
↳17430		L1, Model 1Change entry address of task in interrupt chain. Model 3: Remove task from interrupt chain. N1, N3: Keep drives rotating and reselect current drive.
4417H
↳17431		L3Contains current day in coded format.
4419H
↳17433		Model 3, L3Write disk directory to screen or buffer. N1, N3: Execute DOS command and return to caller.
441CH
↳17436		 FSPEC fetches a file specification in TRSDOS standard format. To Use:
CALL 441CH
441CH
↳17436		Model 3, L1, L3, Model 1/3, N1, N3, Model 1/3Move filespec to FCB.
441FH
↳17439		Model 3 DiskOSVER$: Holds the DOS Version Number. Stored in DCB format. Note on a Model 1 this is stored in 403EH and on the Model 4 at 0085H
4420H
↳17440		 INIT creates a new file in the directory and opens the DCB for this file. If the filespec name is found then the file is simply opened for use, else a new file is created first. To Use:
LD HL,BUFFER
LD DE,DCB
LD B,LRL
CALL 4420H
JP Z,OK ;no error
JP C,NEWFIL ;no error, but new file was created
;A= TRSDOS error code
4420H
↳17440		AllOpen or create a file.
4424H
↳17444		AllOPEN opens the DCB of an existing file. To Use:
LD HL,BUFFER
LD DE,DCB
LD B,LRL
CALL 4424H
JP Z,OK ;no error
JP NZ,NOFILE ;file does not exist
;A= TRSDOS error code
4428H
↳17448		AllCLOSE: Closes a file. Updates the directory and then closes the file from any more processing. To Use:
LD DE,DCB
CALL 4428H
JP Z,OK ;no error
;A= TRSDOS error code
442CH
↳17452		AllKILL: Remove a file from a directory. Deletes the directory for an open file and then closes the DCB. To Use:
LD DE,DCB
CALL 442CH
JP Z,OK ;no error
;A= TRSDOS error code
442FH
↳17455		Model 3DUAL/ROUTE Flag. 80H=ROUTE is ACTIVE, FFH=DUAL is ACTIVE, 00H=Neither is active.
4430H
↳17456		All(undocumented in Model 1) Load and Execute a Model I Program into Memory. Can be used with CALL 4430H.
4433H
↳17459		All(undocumented in Model 1) Load and Execute a Model I Program. Can be used with JP 4433H.
4436H
↳17462		AllRead logical record into memory. This will transfer one logical or physical disk record into memory. To access:
LD HL,urec
LD DE,dcb
CALL 4436H
JP Z,ok ;No error
If there is an error, Register A will contain the TRSDOS Error Code.
4439H
↳17465		AllWrite logical record to disk. This will transfer one logical or physical disk record from memory. To access:
LD HL,UREC
LD DE,DCB
CALL 4439H
JP Z,ok ;No error
If there is an error, Register A will contain the TRSDOS Error Code.
443CH
↳17468		 VERF is the same as WRITE except that it verifies what was written to disk. To use:
LD HL,UREC
LD DE,DCB
CALL 443C
BP Z,OK ;No error
If there is an error, Register A will contain the TRSDOS Error Code.
443CH
↳17468		AllWrite record and verify.
443FH
↳17471		Model 3, L1, L3, Model 1/3, N1, N3, Model 1/3Point to first record in file.
4442H
↳17474		 POSN positions a file to read or WRITE a randomly selected logical record. To use:
LD DE,DCB
LD BC,nnnn ;logical rec'd # to position for
CALL 4442H
JP Z,OK ;no error
;A= TRSDOS error code
4442H
↳17474		AllPosition file to specified record.
4445H
↳17477		Model 3, L1, L3, Model 1/3, N1, N3, Model 1/3Backspace file one record.
4448H
↳17480		Model 3, L1, L3, Model 1/3, N1, N3, Model 1/3Position to end of file.
444BH
↳17483		Model 3, L3, Model 3, Model 3Add extension to filespec in FCB (see also 4473). L1: Check for end of file. Model 1: Multiply 16 bit by 8 bit integer. N1, N3: Allocate disk space to file.
444DH
↳17485		Model 3[This is the start of RAM for a Model 3 as far as the memory test goes].
444EH
↳17486		Model 3, L3, Model 3Multiply 16 bit by 8 bit integer. L1: Update directory with current record as end of file. Model 1: Divide 16 bit by 8 bit integer. N1, N3: Position file to specified byte record.
4451H
↳17489		Model 3, L3, Model 3Divide 16 bit by 8 bit integer. Model 1: Check for end of file. N1, N3: Update directory with record as end of file.
4454H
↳17492		L1Read current sector. L3, Model 3, Model 3: Parse parameters in command line. Model 1: Find drive and file number of a file.
4457H
↳17495		L1Rewrite current sector. Model 3: Check for end of file. Model 1: Read directory to user buffer.
4458H
↳17496		L3Check for end of file.
445AH
↳17498		L1Calculate current logical record number. Model 1/3: Display directory on CRT.
445BH
↳17499		L3Update directory with current record as end of file. N1, N3: Select and power up specified drive.
445DH
↳17501		L1Calculate EOF record number.
445EH
↳17502		L3Reread current sector. N1, N3: Test drive and disk.
4460H
↳17504		L1Skip next logical record.
4461H
↳17505		L3Rewrite current sector. N1, N3: Add user routine to DOS library chain.
4462H
↳17506		Model 1/3Send text to printer.
4463H
↳17507		L1Read directory to buffer or CRT.
4464H
↳17508		L3Skip next logical record. N1, N3: Remove user routine from DOS library chain.
4467H
↳17511		L1, L3, Model 1/3, N1, N3, Model 1/3Display text on CRT.
446AH
↳17514		L1, L3, N1, N3, Model 1/3Send text to printer.
446DH
↳17517		 TIME will return the current time in ASCII. To use:
LD HL,nnnn ;address of 8 byte buffer
CALL 446DH ;put time in buffer
446DH
↳17517		Model 1, L1, Model 1/3, N1, N3, Model 1Get time in ASCII format. L3: Calculate current logical record number.
4470H
↳17520		 DATE will return the current date in ASCII. To use:
LD HL,nnnn ;address of 8 byte buffer
CALL 4470H ;put date in buffer
4470H
↳17520		L3Calculate end of file record number.
4473H
↳17523		L3Holds image of interrupt latch. Model 1, L1, Model 1/3, N1, N3, Model 1/3: Add default extension to filespec in FCB. (See also 444BH)
4476H
↳17526		L1, Model 1, Model 1/3Parse parameters in command line.
4478H
↳17528		 NewDOS/80 v2.0 for Model 3 Break Vector (195=Off, 201=On).
4478H
↳17528		Model 1MODEL 3 NEWDOS/80 V2.0 BREAK VECTOR
 – 195=OFF, 201=ON
447BH
↳17531		L1Send text to job log and CRT. N3: Add task interrupt chain.
447CH
↳17532		Model 1/3Compare filespec to wildcard mask.
447EH
↳17534		L1Send text to joblog.
447FH
↳17535		Model 1/3Get device number for file or I/O device.
4480H
↳17536		Model 1System DCB Address for TRSDOS v2.3
4482H
↳17538		Model 1/3Sort block of memory.
4485H
↳17541		Model 110 disk I/O functions depending on value in A.
4488H
↳17544		Model 310 disk I/O functions depending on value in A. Model 1: Locate device control block for any device.
448BH
↳17547		Model 1Locate drive control table for any drive.
44A0H
↳17568		Model 3Locate device control block for any device.
44A3H
↳17571		Model 3Locate drive control table for any drive.
44B8H
↳17592		L1Check drive and disk.
44BBH
↳17595		L1Get file name from directory.
44C1H
↳17601		L1Multiply 16 bit by 8 bit integer.
44C4H
↳17604		L1Divide 16 bit by 8 bit integer.
44D2H
↳17618		Model 3Add task to interrupt chain.
44D5H
↳17621		Model 3Remove task from interrupt chain.
44D8H
↳17624		Model 3Change execution address of task in interrupt chain.
44DBH
↳17627		Model 3Set task pointer to default of RET.
44DEH
↳17630		Model 1/3Verify a sector without reading to RAM.
44E1H
↳17633		Model 1/3Read sector.
44E4H
↳17636		Model 1/3Write sector.
44E8H
↳17640		Model 1/3Read directory sector.
44EBH
↳17643		Model 1/3Write directory sector.
44EEH
↳17646		Model 1/3Read directory.
44F1H
↳17649		Model 1/3Write directory.
44F4H
↳17652		Model 1/3User function.
44F7H
↳17655		Model 1/3Get directory track number.
4500H-4517H
↳17664-17687		Level 2DOS interrupt table contains address pairs for interrupt routines (i.e. CLOCK, TRACE, etc.). You can place your own routine addresses in this table. An example is below:
DI ;disable interrupts
LD HL,4510H ;address of table link
LD (HL),myrout ;address of interrupt routine
EI ;enable interrupts
45F8H
↳17912		Model 3Part of the WP (write protect) code. This byte is checked before doing a write.
46DDH
↳18141		 RDSECT. On Model I, allows you to read a disk sector. Register C contains the drive selected, D contains the track, E contains the sector number, HL points at data buffer. On return, Z is set if successful; otherwise A contains error code.
46E6H
↳18150		 WTSECT. On Model I, allows you to write a disk sector. Same conditions as RDSECT at 46DDH.
4754H
↳18260		L1, L3Select drive.
4759H
↳18265		L1, L3Continually reselect drive until it is ready.
475EH
↳18270		L1, L3Seek specified cylinder (track).
4763H
↳18275		L1, L3Write sector to disk.
4768H
↳18280		L1, L3Write system (directory) sector.
476DH
↳18285		L1, L3Write track to disk (used for formatting).
4772H
↳18290		L1, L3Verify sector without transferring data to memory.
4777H
↳18295		L1, L3Read sector to buffer.
4779H
↳18297		L1Send text to file or device. Model 1/3: Scan and evaluate command line.
478FH
↳18319		L1, L3Get address of drive code table for specified drive.
479CH
↳18332		L1, L3Get byte field from drive code table.
4AC1H
↳19137		 This routine will read sectors 2 - 9 of the disk directory track (11H) into your designated buffer. It is just like the DOS routine at 5CC8 which is overlaid by BASIC/CMD. (not for Newdos 80). To Use:
LD B,0
LD DE,BUFFER ;256*8 bytes
read CALL 4AC1H ;read sector
LD L,0
PUSH BC
LD BC,256
LDIR
POP BC
INC B
LD A,B
CP 8
JR NZ,read
RET
4B10H
↳19216		L1, L3Read directory sector with specified entry code.
4B1FH
↳19231		L1, L3Write system buffer to specified directory sector.
4B45H
↳19269		L1, L3Read directory sector to user buffer.
4B64H
↳19300		L3Get cylinder (track) number of directory.
4B65H
↳19301		L1Get cylinder (track) number of directory.
4B6BH
↳19307		L3Multiply 8 bit by 8 bit integers.
4B6CH
↳19308		L1Multiply 8 bit by 8 bit integers.
4B7AH
↳19322		L3Divide 8 bit by 8 bit integers.
4B7BH
↳19323		L1Divide 8 bit by 8 bit integers.
4CE7H
↳19687		Model 3Storage Location for Video Driver. Used when invoking DUAL.
4CF8H
↳19704		Model 3Storage Location for Printer Driver. Used when invoking DUAL.
4D00H-4DFFH
↳19712-19967		Model 1BOOT/SYS Resides Here in Memory
4E00H-50A7H
↳19968-20647		Model 1SYS1/SYS Resides Here in Memory
4FFFH
↳20479		Model 1/34K System Top of Memory
5200H-6FFFH
↳20992-28671		Level 2Disk BASIC or DOS utilities when loaded, or user memory
5203H
↳20995
↳ERRTAB		Model 1TRSDOS BASIC Extended Error Messages. These get used instead of the L2 built-in messages.
54C3H
↳21699		Model 1DOS Vector - CVI Command
57F0H
↳22512		Level 261 character ASCII copyright notice (DOS)
582CH
↳22572
↳SCRMBL		Model 1The copyright message "THIS BASIC WAS AUTHORED AND IS COPYRIGHTED BY MICROSOFT, 1978"
586BH
↳22635
↳PROTMS		Model 1The message "PROTECTION HAS CLEARED MEMORY"
5A77H
↳23159
↳DIRTMP		Model 1The status of FILE 0 (open or closed) in TRSDOS v2.3 BASIC
5B77H
↳23415
↳USRTAB		Model 1The start of the USR(0)...USR(15) Jump Table
5B8BH
↳23435
↳MAXTRK		Model 1A Byte which toggles whether the command being processed was a GET or a PUT
5B8CH
↳23436
↳DSKERR		Model 1Storage location for the DOS error code
5B8DH-5B8EH
↳23437-23438
↳PTRFIL		 The address in RAM of the file being used
5B8FH
↳23439
↳FILPTR		Model 1Start of the File Block Pointer Table for Files 01 to 15 (i.e., OPEN "I",n,"FILENAME")
5BAFH
↳23471
↳FILPT1		Model 1Copy of the FILPTR for File 0
5BB1H
↳23473
↳LSTFRE		Model 1A flag as to whether to run a BASIC program or not once the current operation is done
5C98H
↳23704
↳PTCMD		Model 1A flag to see if TRSDOS v2.3 was restarted or cold booted
5C99H
↳23705
↳SVTXTT		Model 1BASIC Program Beginning Pointer
5C9BH
↳23707
↳FILSVS		Model 1The answer to the FILES? question entered by the user when entering BASIC
5C9DH
↳23709
↳OLSTTP		Model 1Pointer to the lowest address available for string storage a/k/a top of free memory
5D51H
↳23889
↳NXTFCN+1		Model 1Exit JUMP Address Storage location for a CMD"S" or CMD"A" return to DOS from BASIC
5E57H
↳24151
↳BADMVS		Model 1Pointer to the message "USE TRSDOS 2.2 OR LATER"
5E70H
↳24176
↳FILMES		Model 1Pointer to the message "HOW MANY FILES"
5E7FH
↳24191
↳MESG		Model 1Pointer to the message "RADIO SHACK DISK BASIC VERSION 2.2"
5EA3H
↳24227
↳FILNAM		Model 132 character buffer to store the current filename
651EH
↳25886
↳FLRL		Model 1Storage for the record size used in a FIELD command
651FH
↳25887
↳DOPROT		Model 1Flag as to whether an action is permitted based on the protection level of the file in the directory
6520H
↳25888
↳PROTFL		Model 1A different format of the protection level flag for the current file
6574H
↳25972
↳DERTAB-1		Model 1The byte before the table of DOS specific error message table that uses SYS4 to process the error instead of BASIC
6575H
↳25973
↳DERTAB		Model 1Table of DOS specific error message table that uses SYS4 to process the error instead of BASIC
68D9H
↳26841		Model 3RAM - BASIC PROGRAM IN TRS-DOS 1.3
7A00H
↳31232		Model 3Network 4 Read Buffer
7FFFH
↳32767		Model 1/316K SYSTEM TOP OF PHYSICAL MEMORY
BFFFH
↳49151		Model 332K System Top of Memory
FFFFH
↳65535		Model 348K System Top of Memory

RAM Addresses and Routines for Level 1

Address
(Hex/Dec)		Description
3C00H
↳15360		Start of screen memory
3FFFH
↳16383		End of screen memory
4000H
↳16384		A value
4004H
↳16388		B value
4008H
↳16392		C value
400CH
↳16396		D value
4010H
↳16400		E value
4014H
↳16404		F value
4018H
↳16408		G value
401CH
↳16412		H value
4020H
↳16416		I value
4024H
↳16420		J value
4028H
↳16424		K value
402CH
↳16428		L value
4030H
↳16432		M value
4034H
↳16436		N value
4038H
↳16440		O value
403CH
↳16444		P value
4040H
↳16448		Q value
4044H
↳16452		R value
4048H
↳16456		S value
404CH
↳16460		T value
4050H
↳16464		U value
4054H
↳16468		V value
4058H
↳16472		W value
405CH
↳16476		X value
4060H
↳16480		Y value
4064H
↳16484		Z value
4068H
↳16488		Pointer to cursor position
406AH
↳16490		Points to top of physical memory
406CH
↳16492		Pointer to top of used memory
406EH
↳16494		Current FOR end value
4070H
↳16496		A$ Value (16 bytes)
4080H
↳16512		B$ Value (16 bytes)
4090H
↳16528		Cassette port status cache (byte)
4091H
↳16529		Current FOR step value
4093H
↳16531		Pointer to top of current FOR statement
4095H
↳16533		Pointer to current FOR statement
4097H
↳16535		Save for pointer to current line
4099H
↳16537		Pointer to print buffer
409BH
↳16539		Pointer to NEXT variable
409DH
↳16541		Parse pointer saved at a STOP
409FH
↳16543		Pointer to current line being executed
40A1H
↳16545		READ pointer
40A3H
↳16547		Saved SP for this BASIC frame
40A5H
↳16549		Pointer to current FOR variable
40A7H
↳16551		Three bytes of RNG state
40AAH
↳16554		Unused
40ACH
↳16556		Buffer for command input, print output to cassette
40F3H
↳16627		End of buffer
40F4H
↳16628		Bottom of floating point stack. Each entry is 5 bytes consisting of LSB, Middle, MSB (with Bit 7 set), Exponent and Sign (in Bit 7)
4180H
↳16768		Bottom of system stack pointer
4200H
↳16896		Top of system stack pointer
4201H
↳16897		Start of BASIC Program Storage. 16 bit line number followed by line text, terminated with a 0DH