RAM Addresses and Routines

The following keys for DOSes apply:

T1 – Model 1 TRSDOS

T3 – Model 3 TRSDOS

N1 – Model 1 NEWDOS

N3 – Model 3 NEWDOS

L1 – Model 1 LDOS

L3 – Model 3 LDOS

M1 – Model 1 MULTIDOS

M3 – Model 3 MULTIDOS

D1 – Model 1 DOSPLUS

D3 – Model 3 DOSPLUS

All – All DOSes, Model I and Model III.

RAM Addresses and Routines:

Address (Hex/Dec)	Official Symbol	Model Code	Description
3000H-37DDH ↳12288-14301		1	Reserved. Unused in Model I.
3000H ↳12288		3	Write 500 baud cassette leader and sync byte.
3003H ↳12291		3	Write 1500 baud cassette leader and sync byte.
3006H ↳12294		3	Search for 500 baud cassette leader and sync byte.
3009H ↳12297		3	Search for 1500 baud cassette leader and sync byte.
300CH ↳12300		3	Turn off cassette.
300FH ↳12303		3	Turn on cassette.
3012H ↳12306		3	Disk bootstrap routine.
3015H ↳12309		3	Power-up routine (jump here from 0002H).
3018H ↳12312		3	Maskable interrupt handler.
301BH ↳12315		3	RS-232-C initialization driver routine.
301EH ↳12318		3	RS-232-C input driver routine.
3021H ↳12321		3	RS-232-C output driver routine.
3024H ↳12324		3	Keyboard driver routine.
3027H ↳12327		3	I/O Route driver routine (not available on Model 4).
3029H ↳12329		3/4	To determine if a computer is a Model 3 or Model 4, peek this location. If it is 0, it is a Model 4.
302AH ↳12330		3	Part of routine to search for cassette leader and sync byte (jumps here from 0229H).
302DH ↳12333		3	Part of LIST command (jumps here from 2B91H).
3030H ↳12336		3	Basic 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		3	Non-maskable interrupt handler.
3042H ↳12354		3	$SETCAS routine (prompt user to set cassette baud rate)
37DEH ↳14302		1	Communication Status Address
37DFH ↳14303		1	Communication Data Address
37E0H ↳14304		1	Interrupt Latch Address
37E1H ↳14305	DSEL$	1	Disk Drive Select Latch Address. Value of 01H is Drive :0
37E4H ↳14308		1	Cassette Select Latch Address (Values: 0-1 – SELECT TAPE DRIVE: 0=#1 1=#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	$PROUT: Output a Byte to the Printer.
37EAH ↳14314		1	Contains the byte from 37E8H (PRTAD)
37EBH ↳14315		1	Contains the byte from 37E8H (PRTAD)
37ECH ↳14316	FDCAD$	1	Floppy 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 boostratp routine (unless the BREAK key is held). If either 00H or FFH is found, then no disk controller is found, and the TRS-80 will jump to Level II BASIC. Bit 1 from this memory location is DATA READY. Passing 1BH to this memory location is a command to SEEK. Passing 88H to this memory location is a command to READ SECTOR. Passing D0H to this memory location is a command to FORCE INTERRUPT.
37EDH ↳14317		1	DISK TRACK SELECT
37EEH ↳14318	FDCAD$+2	1	DISK SECTOR SELECT
37EFH ↳14319	FDCAD$+3	1	Byte read from disk (DISK DATA)
3800H-3840H ↳14336-14400 – 15105-15168	KEYAD$	1/3	Keyboard Memory / Address Matrix
3B80H ↳15232		1/3	Keyboard Memory / Address Matrix for SHIFT Keys
3C00H-3FFFH ↳15360-16383	DSPAD$	1/3	$VIDRAM: The beginning of video ram.
3C00H ↳15360			This is the beginning of video ram or VIDRAM. It ends at 3FFFH or 16383.
3FCDH-3FCEH ↳16333-16334			End of BASIC Program Pointer (LSB,MSB)
3FFFH ↳16383		3	END OF VIDEO MEMORY
4000H ↳16384			RST 08 Compare value pointed to by HL to that immediately following RST instruction.
4000H	RST1$	1	RST 8 vector
4000H ↳16384	RST1$	TD	RST 08 (Syntax Check): Compare value pointed to by HL to that immediately following RST instruction.
4000H ↳16384	RST1$	1	Start of Level II BASIC Fixed RAM.
4003H-4005H ↳16387-16389		TD	RST 10H (Get Next Character): Jump Vector.
4003H ↳16387			RST 10 Examine next symbol pointed to by HL.
4003H		1	RST 10 vector
4003H		1	The next 3 bytes are used to hold the length and addr of a string when it is moved to the string area.
4006H		1	RST 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 varible.
4009H		1	RST 20 vector
4009H ↳16393			RST 20H (Get Current Type) Jump Vector.
400CH-400EH ↳16396-16398	RST5$	1/3	RST 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 III, 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$	1	RST 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$	1	Load debug (ld a,xx/RST 28)
400FH ↳16399	RST6$	Model III	RST 30H Jump Vector.
4012H-4014H ↳16402-16404	RST7$ or INTERP	1/3	RST 38H Jump Vector.
4012H	RST7$ or INTERP	1	RST 38 interrupt service call
4012H ↳16402			RST 38 Maskable interupt vector.

4015H-401CH – Keyboard Device Control Block

Address (Hex/Dec)	Official Symbol	Model Code	Description
4015H-401CH ↳16405-16412	KDCB$	1/3	Keyboard Device Control Block (DCB)
4015H ↳16405	KDCB$	Model III	Tape RAM – Keyboard DCB Type = 1 = Read Only
4015H	KDCB$	1	Keyboard dcb (8 bytes)
4015H ↳16405			Beggining of Keyboard DCB. One byte device type. = 1
4016H ↳16406		Model III	Two byte keyboard driver vector. Model III its 3024H, which JUMPs to 338EH which then processes the keyboard)
4016H-4017H ↳16406-16407		Model I	Keyboard Device Control Block Two byte keyboard driver vector. To Disable The Model I Keyboard: N1=PEEK(16406) N2=PEEK(16407) POKE16406,154 POKE16407, 10 To Enable The Model I Keyboard: POKE 16406,N1 POKE 16407,N2
4015H ↳16405	KDCB$	Model I	Keyboard DCB+0: This address holds the DCB Type
4016H ↳16406		Model I	Keyboard DCB+1: This address holds byte 1 of the 2 byte Driver Address
4016H ↳16406			Two byte keyboard driver vector.
4017H ↳16407		Model I	Keyboard DCB+2: This address holds byte 2 of the 2 byte Driver Address
4018H ↳16408			Right SHIFT toggle.
4018H ↳16408		Model I	Keyboard DCB+3: This address holds “0”
4018H ↳16408		1/3	Keyboard DCB: Right Shift Toggle
4019H ↳16409		Model I	Keyboard DCB+4: This address holds “0”
4019H ↳16409			Caps lock switch (Not 0 = Caps only)
4019H ↳16409		Model III	Caps 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 I	Keyboard DCB+5: This address holds “0”
401AH ↳16410		Model III	Cursor Blink Count.
401AH ↳16410			Cursor blink count
401BH ↳16411		Model I	Keyboard DCB+6: This address holds “K”
401BH ↳16411		Model III	Cursor Blink Status. (0=Off Nz=On)
401BH ↳16411			Cursor blink status. (0=blinks)
401CH ↳16412		Model I	Keyboard DCB+7: This address holds “I”
401CH ↳16412		1/3	Cursor Blink Switch. Set to 0 for blink, and anything else for no blink.
401CH ↳16412			Cursor blink switch (0 = blink)

401DH-4024H – Video Display Control Block

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

4025H-402CH – Printer Control Block

Address (Hex/Dec)	Official Symbol	Model Code	Description
4025H ↳16421	PDCB$ IX+0	1/3	Printer DCB. IX+0 = DCB Type (6). Classification = Write Only
4025H ↳16421			Beggining of Printer DCB. One byte device type. = 6.
4026H ↳16422			Two byte printer driver vector.
4026H-4027H ↳16422-16423	IX+1 IX+2	1/3	Print Driver Address (stored in LSB/MSB Order).
4028H ↳16424	IX+3	1/3	Printer: Maximum Number of Lines which can be Printed per Page plus 1. The default is 67. 0 if top-of-page
4028H ↳16424			Maximum lines printed per page plus one. Default=67.
4029H ↳16425			Number of lines printed plus one.
4029H ↳16425	IX+4	1/3	Printer: Number of lines already printed +1. To reset the counter, POKE 16425,1.
402AH ↳16426		1/3	Model 1: Not Used
402AH ↳16426		Model III	Printer DCB: # Characters Printed+1
402AH ↳16426			Character counter + 1.
402BH ↳16427			Line printer maximum line length less two.
402BH ↳16427		Model III	Line printer maximum characters (width) per line less 2. Set at 255 for no maximum.
402CH ↳16428			“R”
402DH ↳16429			Return to Dos exit. (Disk systems only).
402DH ↳16429	SYS1IN		EXIT: Normal program exit back to DOS. (Disk systems only).
402DH ↳16429	SYS1IN	Model III	Tape RAM – Printer DCB: Jp 5000h Unused Dos Vector
4030H	ABORT	1	DOS 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			For all DOSes except TRSDOS, is abnormal return to DOS ready.
4030H ↳16432		Model III	Tape RAM – Printer DCB: RST 0
4032H		1	Write ‘DOS ready’ msg
4033H	CIO$	1	Call device driver ala DOS
4033H ↳16435		Model III	Tape RAM – Printer DCB: XOR A and RET
4036H-403CH ↳16438-16444	KYBT$	1/3	Keyboard 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 3240H: Enter, Clr, Brek, Up, Down, Left, Right, and Space keys.
4036H ↳16438			Keyboard buffer (7 bytes).
403DH ↳16445		Level 2	Cassette port and print size flag (bit 3) copy (For Model III, 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. So if the value is 0, then the video is in 64 characters per line. If the value is 8, then the video is in 32 characters per line.
403DH ↳16445	CAST$	M1 DOS / Model III	Tape RAM – Interrupt Vector 3 – JP 35FAH. This MAY be the routine to add a task to the interrupt chain.
403DH ↳16445	CAST$	M3 DOS	Used 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 4210). L3: location of routine to add task to interupt chain.
403EH-407FH ↳16446	CURDOS	M1	Unused in non-Disk systems. Real time clock storage locations are kept here. For the Model III this would be 4216H-421CH.
403EH	CURDOS	1	Used by DOS
403EH ↳16446	CURDOS	D1	OSVER$: Holds the DOS Version Number. Stored in DCB format. Note on a M3 this is stored in 441FH and on the M4 in 0085H
403EH ↳16446			For Model I DOSPLUS, hold DOS version in DCB format.
403FH		1	Used by DOS
4040H		1	System bst’s
4040H ↳16448		Model I	25 ms heartbeat counter.
4040H ↳16448		Model III	Interrupt Vector 6 – JP 35FAH. Vector 6 may be “remove task from interrupt chain”.
4040H ↳16448		For L1 & M1	25 ms heartbeat counter. For L3, used to remove task from interrupt chain.
4041H-4043H ↳16449-16451	XTIME	L1, D1, and M1	TIME$, time of day: Seconds, Minutes, Hours
4041H	XTIME	1	Seconds
4041H ↳16449			Beginning of Time and Date bytes. (seconds, min., hours, year, day, month) Ends at 4046H or 16454. L1, D1, and M1
4042H		1	Minutes
4043H		1	Hours
4043H ↳16451		L3	Change address of interupt task.
4043H ↳16451		Model III	Tape RAM – Interrupt Vector 7 – JP 35FAH
4043H ↳16451		L3	change address of interupt task.
4044H-4046H ↳16452-16454		L1, D1, and M1	DATE$, date: Year, Day, Month. Stored in BCD.
4044H		1	Year
4044H ↳16452		L1, D1, & M1	Contains date in binary format.
4045H		1	Day
4046H		1	Month
4046H ↳16454		L3	Remove task from interupt chain.
4046H ↳16454		Model III	Tape RAM – Interrupt Vector 2 – JP 35A9H
4046H ↳16454		L3	Remove task from interupt chain.
4047H		1	Load address for system utilities 2 bytes, initialized to 5200 by sys0/sys
4047H ↳16455		L1	Current day in coded form.
4047H ↳16455		L1	Current day in coded form.
4048H		1	Current interrupt status word
4049H-404AH ↳16457-16458	MEMEND	1	DOS MEMORY SIZE. Highest available memory location (On a Model III it is stored at 4411H)
4049H ↳16457	MEMEND	Model III	Tape RAM – RST 0 NMI Vector (Reset If So)
4049H ↳16457			For the Model III disk is non maskable interupt vector, for Model I disk is highest available memory location (Model III = 4411H)
404BH ↳16459		L1	Contains image of interrupt latch.
404BH ↳16459		L1	Contains image of interrupt latch.
404CH		1	Interrupt subroutine mask
404DH-404EH		T1	Address of interrupt service routine for interrupt bit 0
404DH		1	Reserved (interrupt bit 0)
408EH ↳16526			Address of USR routine (two bytes)
404FH-4050H		T1	Address of interrupt service routine for interrupt bit 1
404FH		1	Reserved (interrupt bit 1)
4050H-4051H ↳16463-16464		Model I	FDC Interrupt Vector
4050H		1	Stack during ipl
4051H-4052H		T1	Address of interrupt service routine for interrupt bit 2
4051H		1	Communications interrupt subroutine
4052H-4053H ↳16465-16466		Model I	Communications Interrupt Vector
4053H-4054H ↳16465-16466		T1	Address of interrupt service routine for interrupt bit 3
4053H		1	Reserved (interrupt bit 3)
4055H-4056H		T1	Address of interrupt service routine for interrupt bit 4
4055H		1	Reserved (interrupt bit 4)
4057H-4058H		T1	Address of interrupt service routine for interrupt bit 5
4057H		1	Reserved (interrupt bit 5)
4058H		1	Addr of clock interrupt routine
4059H-405AH		T1	Address of interrupt service routine for interrupt bit 6
4059H		1	Addr of disk interrupt routine
405BH-405CH		T1	Address of interrupt service routine for interrupt bit 7
405EH ↳16478		Model I	25 MSec Heartbeat Interrupt
4070H		1	Start of stack during ROM ipl
407DH ↳16509	TSTK$	DOS	Stack pointer for DOS, set by the ROM bootstrap routine
407EH		1	Reserved
407FH		1	Reserved
4080H	FDIVC or RAMLOW	1	Subtraction routine used by division code. Code is moved from ’18f7′ – ‘1904’ during non-disk ipl or by baSIC UTILITY FOR DISK SYSTEMS
4081H ↳16513	FDIVC+1	Model 1/3	Used 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 1/3	Used in the single precision division routine.
4085H ↳16517	FDIVB+1	Model 1/3	Used in the single precision division routine (stores the NMSB).
4088H ↳16520	FDIVA	Model 1/3	Used in the single precision division routine.
4089H ↳16521	FDIVA+1	Model 1/3	Used in the single precision division routine (stores the MSB).
408BH ↳16523	FDIVG	Model 1/3	Used in the single precision division routine
408CH ↳16524	FDIVG+1	Model 1/3	Used in the single precision division routine (stored the High Order).

USR and Random Number Routines

Address (Hex/Dec)	Official Symbol	Model Code	Description
408EH-408FH ↳16526-16527	USRTAB	Level 2	(L2 only) Entry point to USR routines. 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	USRTAB	1	Contains address of user subroutine
408EH ↳16526	USRTAB	Model III	Tape RAM – Tape RAM: Address Of USR Subroutine
408EH ↳16526	MAXFIL	T1	TRSDOS 2.3 stores the answer to the FILES? Question
408FH ↳16527	VARREC	T1	TRSDOS 2.3 Flag for whether Variable Files were permitted on Entry into BASIC
4090H	MULTR	1	Random number seed
4090H ↳16528	MULTR	Model III	Tape RAM – Tape RAM: Random Number Seed 2
4093H-4098H ↳16531-16536	STAINP	1/3	Input and output port routines
4096H ↳16534	OUTWRD	1/3	Tape RAM – Tape RAM: Out Support
4099H ↳16537	CHARC	1/3	INKEY$ storage. This holds the most recently typed keyboard character, stored in ASCII.
4099H ↳16537			INKEY$ storage. Most recent keyboard character.
409AH ↳16538			Error code is at this address (for BASIC only)
409AH ↳16538	ERRFLG	1/3	Current Error Code is stored at this address (for BASIC only). It would be returned by the ERR function.
409BH	LPTPOS	1	No. Of chars. In current print line
409BH ↳16539	LPTPOS	Level 2 / Model III	Current TAB position of line printer. This byte contains a count of the number of characters already printed on the current line, and 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 III.
409CH ↳16540	PRTFLG OUTSEL	1/3	This is the device output flag. It will contain -1 (or 129) for Cassette Output, 0 for Video Output, 1 for Printer Output.
409CH ↳16540			OUTSEL. On Model I, is a 1-byte output device flag. -1 (or 129) for cass, 0 for video, 1 for printer.
409DH ↳16541	LINLEN	Level 2	Maximum 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	CLMLST	1	Size of print line
409EH ↳16542	CLMLST	Model III	The 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, and 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		1	Reserved
409FH ↳16543		Model III	Tape 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)	Official Symbol	Model Code	Description
40A0H-40A1H ↳16544-16545	STKTOP	1/3	String 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 40BlH) at power-up to provide 50 bytes of string storage area. Changed by use of CLEAR n command (with argument).
40A0H ↳16544			Clear address pointer. Beggining of CLEARed area for string variable storage
40A2H-40A3H ↳16546-16547	CURLIN	1/3	Current Line Number in a BASIC Program in 2 Bytes (LSB/MSB) or FFFFH if in direct mode.
40A2H ↳16546			Last executed line number.
40A4H-40A5H ↳16548-16549	TXTTAB	1/3	BASIC Program Beginning Pointer 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, first POKE 16548,PEEK(16633)-2 : POKE16549,PEEK(16634). Then CLOAD. Then POKE16548,233 : 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.
40A4H ↳16548			Pointer to beggining of Basic program.
40A6H ↳16550	TTYPOS	1/3	Current cursor position on video display line (as returned by the POS function).
40A6H ↳16550			Cursor’s current column number.
40A7H-40A8H ↳16551-16552	BUFPNT	1/3	Input 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.)
40A7H ↳16551			Input buffer pointer.
40A9H ↳16553	CASFLG	1/3	Used 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 DATA 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	1/3	Seed Number 1 for Random Number
40AAH	RNDX	1	Random number seed
40AAH ↳16554			3 byte random seed number.
40ABH	RNDX+1	1	Value from refresh register
40ABH ↳16555	RNDX+1	1/3	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).
40ABH ↳16555			This byte is changed by RANDOM.
40ACH	RNDX+2	1	Last random number (2 bytes)
40ADH ↳16557		1/3	Unused in non-disk systems.
40AEH	DIMFLG	1	Flag: 0 – locate named variable, -1 – create entry for named variable
40AEH ↳16558	DIMFLG	1/3	This 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	VALTYP	1	Type flag for value in Work-Register-Area-1. 2 – Integer 3 – string 4 – single precision 8 double precision
40AFH ↳16559	VALTYP SAFLAG	1/3	Contains the variable tyle flag for the software accumulator. It will contain a 2 for integer, 3 for string, 4 for single-precision, and 8 for double precision.
40AFH ↳16559			SAFLAG. Contains typeflag of software accumulator.
40B0H	DORES	1	Holds intermediate value during expression eva
40B0H ↳16560	DORES	1/3	Used to flag DATA statements while encoding BASIC lines, and to store operator number during expression evaluation.
40B1H-40B2H ↳16561-16562	MEMSIZ MEMTOP	1/3	Top 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 2	Pointer 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 2	String 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 ↳16585-16587	DSCTMP		VARPTR storage area for string currently being created by BASIC. (first byte contains length, second and third bytes contain address of string).
40D3H ↳16585			Saves length ASCII representation of binary integer.
40D4H ↳16586			Two byte address. Points to buffer where ASCII decimal representation written.
40D6H-40D7H ↳16598-16599	FRETOP	1/3	Pointer 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 ( 40BlH-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 2	This pair (two byte) of locations is used a 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	TEMP3	1	1: Index of last byte executed in current statement. 2: Edit flag during print using
40D8H ↳16600			Two byte location of where Basic is currently reading program.
40DAH-40DBH ↳16602-16603	DATLIN	Level 2	Line 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.
40DAH	DATLIN	1	Line no. Of last data statement
40DCH	SUBFLG	1	FOR command flag (1 = FOR loop is in progress 0 = NO FOR loop in progress)
40DCH ↳16604	SUBFLG	Level 2	If 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	BFKLFL	1	0 During input phase, zero otherwise
40DDH ↳16605	BFKLFL	Level 2	Flag indicates whether inputing text. Used by RETURN and RESUME NEXT commands.
40DEH	FLGINP	1	Read 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 2	Used 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	1/3	Used 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	TEMP	1	Holds execution addr for pgm loaded with DOS request
40DFH ↳16607			Default entry point for SYSTEM tapes.
40E1H	AUTFLG	1	Auto increment flag 0 = no auto mode non-zero holds next line
40E1H ↳16609	AUTFLG		AUTO on or off flag. 0=AUTO is off.
40E1H ↳16609			Auto flag.
40E2H-40E3H ↳16610-16611	AUTLIN	Level 2	Line Number: Current line number for the AUTO command.
40E2H	AUTLIN	1	Current line number in binary (during input phase)
40E2H ↳16610			Current auto line number.
40E4H ↳16612	AUTINC		AUTO command increment value
40E4H ↳16612			Auto increment.
40E6H-40E7H ↳16614-16615	SAVTXT	1/3	Pointer to terminator (end of line 00H byte or “:”) of the last executed Basic statement is at this address.
40E6H	SAVTXT	1	During input: addr of code string for current statement. During execution: line no. 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	1/3	Pointer to the beginning of the STACK POINTER.
40E8H	SAVSTK	1	During execution: holds stack pointer value when statement execution begins
40E8H ↳16616			Beggining of Basic’s stack.
40EAH-40EBH ↳16618-16619	ERRLIN	1/3	Line 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	ERRLIN	1	Line no. In which error occurred
40EAH ↳16618			Two byte address. Contains line number with error.
40ECH-40EDH ↳16620-16621	DOT	Level 2	Stores the current line number. Can also be the Line Number for the EDIT command.
40ECH ↳16621			Two byte address. “.” line number.
40EEH-40EFH ↳16622-16623	ERRTXT	Level 2	Pointer to last byte executed when error occured. Used by RESUME command.
40EEH ↳16622			Pointer to I/O buffer.
40F0H-40F1H ↳16624-16625	ONELIN	Level 2	Line 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 occured. Set to -1 (FFH) on error, otherwise set to zero (such as after RESUME statement has been executed). POKEing the appropriate values into this loca0ion 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	TEMP2	1	Addr of decimal point in pbuff
40F5H-40F6H ↳16629-16630	OLDLIN	Level 2	Last line number executed prior to execution of STOP or END statement or termination using the BREAK key.
40F7H-40F8H ↳16631-16632	OLDTXT	Level 2	Pointer to end of last statement executed (points to the colon or zero byte terminator). Used by CONT command.
40F9H-40FAH ↳16633-16634	VARTAB	Level 2	Starting 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	1/3	Starting address of the ARRAY VARIABLE TABLE (end of simple variables)
40FDH-40FEH ↳16637-16638	STREND	1/3	Pointer 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	1/3	‘DATA’ Pointer (2 Byte Address; LSB, MSB). Points to comma or other terminator at end of last item read – search for next DATA i tern 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=l 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	1/3	Variable declaration list. There are 26 entries (1 for each letter of the alphabet). The location at 4101H appiies 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), or 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 defauits 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	1	Trace flag: 0=off (TROFF), non-zero=on (TRON)
411CH	DFACLO-1	1	Temp 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	1/3	Software Accumulator (SA) – 2 Bytes
411DH	DFACLO	1	Work-Register-Area-1 – lsb of dbl prec. Value
411DH ↳16669			First byte of SA.
4124H ↳16673			Last byte of SA.
4127H ↳16679			First byte of SA1.
412EH ↳16686			Last byte of SA1.
4120H	FACLO-1	1	Work-Register-Area-1 – dbl prec value
4121H-4122H ↳16673-16674	FACLO	1/3	Single precision number storage area for single precision math routines – 2 Bytes (4121H=MSB)
4123H-4124H ↳16675-16676	FAC-1	Model III	Single precision number storage area for single precision math routines – 2 Bytes (4123H=MSB)
4123H	FAC-1	1	Work-Register-Area-1 – msb for single prec
4124H	FAC	1	Work-Register-Area-1 – exponent for single prec
4125H	FAC+1	1	Sign of result during math & arithmetic operations
4126H	ARGLO-1	1	Bit bucket used during dp addition
4127H-412EH ↳16679-16686	ARGLO a/k/a ARG-7	1/3	Alternate Software Accumulator (SA1 or REG2) – 2 Bytes
4127H	ARGLO	1	Work-Register-Area-2 – lsb
4128H		1	Work-Register-Area-2
4129H		1	Work-Register-Area-2
412AH		1	Work-Register-Area-2
412CH		1	Work-Register-Area-2
412DH	ARG-1	1	Work-Register-Area-2 – msb
412EH	ARG	1	Alternate Software Accumulator – exponent
412FH ↳16687	FBUFFR	Level 2 (Non-Disk)	Unused.
4130H-4149H ↳16688-16689	FBUFFR+1	Level 2	Multipurpose 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 III	Tape 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	FMLTT1	1	Temp. Storage
4150H	FMLTT2	1	Temp. Storage
4151H	FBUFFR+34	1	End of temp area locations 4152 thru 41e2 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)	Official Symbol	Model Code	Description
4152H ↳16722	ERCALL	1/3	Disk BASIC Vector: CVI vector (3 byte jump command to handler)
4152H ↳16722			CVI 3 byte vector.
4155H ↳16725		1/3	Disk BASIC Vector: FN vector (3 byte jump command to handler)
4155H ↳16725			FN 3 byte vector.
4158H ↳16728		1/3	Disk BASIC Vector: CVS vector (3 byte jump command to handler)
4158H ↳16728			CVS 3 byte vector.
415BH ↳16731		1/3	Disk BASIC Vector: DEF vector (3 byte jump command to handler)
415BH ↳16731			DEF 3 byte vector.
415EH ↳16734		1/3	Disk BASIC Vector: CVD vector (3 byte jump command to handler)
415EH ↳16734			CVD 3 byte vector.
415FH		1	Work-Register-Area-1 – dbl prec value
4160H		1	Disk basic exit (mks$)
4161H ↳16737		Model 1/3	Disk BASIC Vector: EOF vector (3 byte jump command to handler)
4161H ↳16737			EOF 3 byte vector.
4164H ↳16740		Model 1/3	Disk BASIC Vector: LOC vector (3 byte jump command to handler)
4164H ↳16740			LOC 3 byte vector.
4167H ↳16743		Model 1/3	Disk BASIC Vector: LOF vector (3 byte jump command to handler)
4167H ↳16743			LOF 3 byte vector.
416AH ↳16746		Model III	Disk BASIC Vector: MKI$ vector (3 byte jump command to handler)
416AH ↳16746			MKI$ 3 byte vector.
416DH ↳16749		Model III	Disk BASIC Vector: MKS$ vector (3 byte jump command to handler)
416DH ↳16749			MKS$ 3 byte vector.
4170H ↳16752		Model 1/3	Disk BASIC Vector: MKD$ vector (3 byte jump command to handler)
4170H ↳16752			MKD$ 3 byte vector.
4173H ↳16755		1/3	Disk BASIC Vector: CMD vector (3 byte jump command to handler)
4173H ↳16755			CMD 3 byte vector.
4176H ↳16758		1/3	Disk BASIC Vector: TIMES$ vector (3 byte jump command to handler)
4179H ↳16761		1/3	Disk BASIC Vector: OPEN vector (3 byte jump command to handler)
4179H ↳16761			OPEN 3 byte vector.
417CH ↳16764		1/3	Disk BASIC Vector: FIELD vector (3 byte jump command to handler)
417CH ↳16764			FIELD 3 byte vector.
417FH ↳16767		1/3	Disk BASIC Vector: GET vector (3 byte jump command to handler)
417FH ↳16767			GET 3 byte vector.
4182H ↳16770		1/3	Disk BASIC Vector: PUT vector (3 byte jump command to handler)
4182H ↳16770			PUT 3 byte vector.
4185H ↳16773		1/3	Disk BASIC Vector: CLOSE vector (3 byte jump command to handler)
4185H ↳16773			CLOSE 3 byte vector.
4188H ↳16776		1/3	Disk BASIC Vector: LOAD vector (3 byte jump command to handler)
4188H ↳16776			LOAD 3 byte vector.
418BH ↳16779		1/3	Disk BASIC Vector: MERGE vector (3 byte jump command to handler)
418BH ↳16779			MERGE 3 byte vector.
418EH ↳16782		1/3	Disk BASIC Vector: NAME vector (3 byte jump command to handler)
418EH ↳16782			NAME 3 byte vector.
4191H ↳16785		1/3	Disk BASIC Vector: KILL vector (3 byte jump command to handler)
4191H ↳16785			KILL 3 byte vector.
4194H ↳16788		1/3	Disk BASIC Vector: & vector (3 byte jump command to handler)
4194H ↳16788			&amp function 3 byte vector.
4197H ↳16791		1/3	Disk BASIC Vector: LSET vector (3 byte jump command to handler)
4197H ↳16791			LSET 3 byte vector.
419AH ↳16794		1/3	Disk BASIC Vector: RSET vector (3 byte jump command to handler)
419AH ↳16794			RSET 3 byte vector.
419DH ↳16797		1/3	Disk BASIC Vector: INSTR vector (3 byte jump command to handler)
419DH ↳16797			INSTR 3 byte vector.
41A0H ↳16800		1/3	Disk BASIC Vector: SAVE vector (3 byte jump command to handler)
41A0H ↳16800			SAVE 3 byte vector.
41A3H ↳16803		1/3	Disk BASIC Vector: LINE vector (3 byte jump command to handler)
41A3H ↳16803			LINE 3 byte vector.
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	RETCNT	1	Disk basic exit (usr) the following addresses are the DOS exit addresses.
41A9H ↳16809			USR 3 byter vector.
41A9H ↳16809		M1, M3	DOS 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		1	DOS exit from 1a1c
41ACH ↳16812			Ready prompt
41ACH ↳16812		Model III	Tape RAM – DOS Links: Link For Ready
41AFH ↳16815			Called from 0368H to input line from keyboard to I/O buffer.
41AFH		1	DOS 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 III	Tape RAM – DOS Links: Link For Inkey$
41B2H ↳16818			Called from 1AA1H immediately after BASIC line is tokenized. HL points to tokenized line.
41B2H		1	DOS exit from ROM address 1aa1
41B2H ↳16818		Model III	Called from 1AA1H immediately after BASIC line is tokenized. HL points to tokenized line.
41B5H ↳16821			Called from 1AECH immediately after BASIC’s table of prg lines are updated. After call to 41B5H, BASIC calls CLEAR routine at 1B5DH then calls this dos exit from 1AF2H
41B5H		1	DOS exit from ROM address 1aec
41B5H ↳16821		Model III	Called 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		1	DOS exit from ROM address 1af2
41B8H ↳16824		Model III	Called at 1AF2H, after above call followed by call to 1B5DH (CLEAR command, leaves HL pointing to start of BASIC program -1).
41BBH		1	DOS exit from ROM address 1b8c
41BBH ↳16827		Model III	Called 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 instrtction here to jump to your own routine.
41BEH		1	DOS exit from ROM address 2174
41BEH ↳16830		Model III	Called 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		1	DOS exit from ROM address 032c
41C1H ↳16833		Model III	Byte 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		1	DOS exit from ROM address 0358
41C4H ↳16836		Model III	ROM 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		1	DOS exit from ROM address 1ea6
41C7H ↳16839		Model III	Called from 1EA6H when RUN is followed by filename or line number
41CAH ↳16842			Related to 41BEH above. Called at beggining of print processing from 206FH to check for possible disk output.
41CAH		1	DOS exit from ROM address 206f
41CAH ↳16842		Model III	Related to 41BEH above. Called at beggining 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		1	DOS exit from ROM address 2103
41CDH ↳16845		Model III	Called 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		1	DOS exit from ROM address 2103
41D0H ↳16848		Model III	Called 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		1	DOS exit from ROM address 2108
41D3H ↳16851		Model III	Called 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		1	DOS exit from ROM address 219e
41D6H ↳16854		Model III	INPUT# 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 III	The 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 recieves value and before assigned to variable, BASIC calls this exit from 222DH.
41DCH		1	DOS exit from ROM address 222d
41DCH ↳16860		Model III	Called at 222DH. Part of READ/INPUT command routine, called just prior to assigning data that has been read or INPUT to variable. After computer recieves 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		1	DOS 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		1	DOS exit from ROM address 0282
41E2H ↳16866		Model III	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.
41E5H-41FCH ↳16869-16892	BUFINI-3	Model III ONLY	Device 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 III	Tape RAM – RS-232 Input DCB: Type = 1 = Read Only
41E6H-41E7H ↳16870-16871		Model III	Tape RAM – RS-232 Input DCB: 2 Byte Driver Address (301EH)
41E8H ↳16872			$RSRCV input buffer (1 byte)
41E8H ↳16872	BUFINI	1/3	Tape RAM – RS-232 Input DCB: RS-232 Input Buffer (1 Character)
41E9H ↳16873		Model III	Tape RAM – RS-232 Input DCB: Bit 2 = Driver On/off Bit 1 = Wait/no Wait
41EAH ↳16874		Model III	This 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 Mode	ASCII 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 III	The “RI” device name.
41EDH ↳16877		Model III	Tape RAM – RS-232 Output DCB: Type = 2 = Write Only
41EEH ↳16878		Model III	Tape RAM – RS-232 Output DCB: 2 Byte Driver Address (3021H)
41F0H ↳16880	RSTX	1/3	RS-232 Output DCB: Output Buffer (1 Character)
41F0H ↳16880			$RSTX output buffer (1 byte)
41F1H ↳16881		Model III	Tape RAM – RS-232 Output DCB: Bit 2 = Driver On/off Bit 1 = Wait/no Wait
41F2H ↳16882		Model III	This sits in the RS-232 OUTPUT DCB, but I have no idea what it does and what uses it
41F3H-41F4H ↳16883-16884		Model III	The “RO” device name.
41F4H ↳16884		1/3	Value 103 ↳ 1st of 2 to Change LINE keyword to act as LPRINT
41F4H ↳16884		4 in 3 Mode	Storage 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		1/3	Value 32 2nd of 2 to Change LINE keyword to act as LPRINT
41F5H ↳16885		Model III	Tape RAM – RS-232 Initialization DCB: Type = 2 = Write Only
41F6H-41F7H ↳16886-16887		Model III	Tape RAM – RS-232 Initialization DCB: 2 Byte Driver Address (301BH)
41F8H ↳16888	BUFINI+20	1/3, T3	$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 sig. nib.
41F9H ↳16889		1/3	Tape RAM – RS-232 Initialization DCB – $RSINIT: Parity/Word Length/Stop-Bit code. Default is 108.
41F9H ↳16889		T3	RS-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		1/3	$RSINIT: Wait Switch (0 = wait, Not 0 = wait)
41FAH ↳16890			$RSINIT wait switch (0 = wait, Not 0 = wait)
41FBH-41FCH ↳16891-16892		Model III	The “RN” device name.
41FDH ↳16893		Model III Only	Used by repeating key routine. Saves LSB of keyboard buffer pointer (buffer at 4036H-403CH) when key is found depressed.
41FEH ↳16894		Model III Only	Used by repeating key routine. Saves contents of current keyboard “row” when key is found depressed.
41FFH-4200H ↳16895-16896		Model III ONLY	Used by repeating key routine. Holds maximum repeat delay count (1500 decimal or 5DCH for first repeat delay, 150 decimal or 96H for subsequent repeats of same character).
4200H-51FFH ↳16896-20991	MEM$	Level 2	TRSDOS 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 interrups, 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 ↳16896-20991		T1	System Sector Buffer Area
4201H-4202H ↳16897-16898		Model III ONLY	Used 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 III ONLY	Three 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 III ONLY	Three byte vector services interrupt # 4. Under non-disk systems contains a jump to 35FAH, which in turn contains a “RET” instruction.
4209H ↳16905		L3	Checks for drive and mounted disk.
4209H-420BH ↳16905-16907		Model III ONLY	Three byte vector services interrupt # 5. Under non-disk systems contains a jump to 35FAH, which in turn contains a “RET” instruction.
4209H ↳16905		L3	Checks for drive and mounted disk.
420CH-420DH ↳16908-16909		Model III ONLY	Pointer 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 III ONLY	Pointer 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 III ONLY	A 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 III 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 III ONLY	Port 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
4210H ↳16912			Various controls: See port EC
4211H ↳16913			Cass baud rate switch (0=500 baud, Not 0=1500 baud)
4211H ↳16913		Model III ONLY	Cassette Info: Cassette Baud Rate Select (0 = 500 baud, Not 0 = 1500 baud)
4212H ↳16914		Model III ONLY	Cassette 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 III ONLY	Cassette 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 III ONLY	Video 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 III ONLY	Unused In non-Disk System
4216H ↳16918		Model III ONLY	Tape RAM – Clock Data: Heartbeat Counter
4217H ↳16919		Model III ONLY	Tape 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 III ONLY	Tape RAM – Clock Data: Minutes (Value: 00-59). You can POKE to change.
4219H ↳16921		Model III ONLY	Tape RAM – Clock Data: Hours (Value: 00-23). You can POKE to change.
421AH ↳16922		Model III ONLY	Tape 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 III ONLY	Tape RAM – Clock Data: Day (Value: 01-31). You can POKE to change.
421CH ↳16924		Model III ONLY	Tape RAM – Clock Data: Month (Value: 01-12). You can POKE to change.
421DH ↳16925		Model III	Tape RAM – I/O Router DCB: Type = 2 = Write Only
421EH ↳16926		Model III	Tape RAM – I/O Router DCB: Driver Address (3739H)
4220H-4221H ↳16928-16929		1/3	$ROUTE: Destination Device Name for ROUTE Routine. 2 Bytes
4220H ↳16928			$ROUTE destination device (two bytes)
4222H-4223H ↳16930-16931		Model III	Tape RAM – I/O Router DCB: Source Device Name. 2 Bytes.
4222H ↳16930			$ROUTE source device (two bytes)
4224H ↳16932		Model III ONLY	Control 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 III Cassette	Undefined, except that the SYSTEM command places its Stack Pointer within this area, at 4288H.
4225H ↳16933		T3, L3, D3	DOS command buffer.
427AH xxxx		T3	BASIC in RAM flag. FFH = BASIC is not in RAM.
4288H ↳17032		L3	33.33 ms heartbeat counter.
4288H ↳17032	BUFINI+160	Model III Cassette	Presumed starting location for a SYSTEM command.
428AH ↳17034		L3	Send message to Job Log and CRT.
428DH ↳17037		T3, D3	Find drive and file number for open file. For L3, send message to Job Log.
4290H ↳17040		T3, L3, D3	Copy directory to RAM buffer.
4293H ↳17043			Get file name from directory.
4296H ↳17046		L3	Execute Dos command and return to DOS ready.
4299H ↳17049		T3	Do DOS command and return to DOS ready. L3: returns to caller is @EXIT and @ABORT vectors change to jump to return address.
429CH ↳17052		T3	Do DOS command and return to caller.
42ADH ↳17069		D3	Contains address of break key routine.
42B3H ↳17075		T3	Which disk drive is the master drive number.
42B4H ↳17076		T3	This is the CLEAR RAM flag.
42E5H-43E8H ↳17125-17384		Model III 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 or TSTACK	1	Always Zero
42E9H ↳17129		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		T3	Protection Override Flag (If Bit 0 is set, password checking is disabled).
4300H ↳17152		T1	Used by TRSDOS 2.3 to store the last track addressed on Drive 0
4301H ↳17153		T1	Used by TRSDOS 2.3 to store the last track addressed on Drive 1
4302H ↳17154		T1	Used by TRSDOS 2.3 to store the last track addressed on Drive 2
4303H ↳17155		T1	Used by TRSDOS 2.3 to store the last track addressed on Drive 3
4304H ↳17156		T1	Used by TRSDOS 2.3 to store the directory Track for Drive 0
4305H ↳17157		T1	Used by TRSDOS 2.3 to store the directory Track for Drive 1
4306H ↳17158		T1	Used by TRSDOS 2.3 to store the directory Track for Drive 2
4307H ↳17159		T1	Used by TRSDOS 2.3 to store the directory Track for Drive 3
4308H ↳17160		T1	Used by TRSDOS 2.3 to store the last disk drive accessed
4309H ↳17160		T1	Used by TRSDOS 2.3 to store the last unit mask for the last drive selected
430AH-430CH ↳17160		T1	Used by TRSDOS 2.3 to store the DCB/Buffer address, current operation
430CH-430DH ↳17160		T1	Used by TRSDOS 2.3 to store the DCB address for the current operation
430EH ↳17160		T1	Used by TRSDOS 2.3 to store the last Overlay Load Request
430FH ↳17167	XMODE	T1	Used 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, D1	Break Key Vector: (195=Off, 201=On).
4313H ↳17171	XFCN	ND1, D1	This is in the middle of a JP nnnn command and the Jump Vector will be put here
4315H ↳17173	XPROT	ND1, D1, T1	This is an OPCODE and can be swapped to RET or JUMP based on a CMD”S” or CMD”A” command
4318H ↳17176		T1, L1, D1	DOS command buffer. Contains the last DOS command entered. Maximum of 64 Characters.
4396H ↳17302		L1	Read directory into memory.
43E9H- ↳ 17385-		3	RAM – 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, D1, D3, N1, N3, M1, M3	Same 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, D1, D3, N1, N3, M1, M3	Do DOS command and return to DOS ready.
4409H ↳17417			Display error message on CRT.
440DH ↳17421		L1, L3, D1, D3, N1, N3, M1, M3	Enter Debug.
4410H ↳17424		L1, D1, N1, M1	Add task to interrupt chain.
4411H-4412H ↳17425-17426		3	MEMORY SIZE M3 DISK BASIC
4411H ↳17425			Address of highest available memory location (Mod III disk only – Mod 1 disk = 4049H)
4413H ↳17427		L1, D1, N1, N3, M1	Remove task from interrupt chain. For D3, add task to interrup chain.
4413H ↳17427		T3	Highest Disk Drive attached to the system.
4414H ↳17428	TSTACK+300	T3	System OVERLAY number Currently in RAM.
4415H ↳17429		T3	Second copy of high memory address. Copied to 4411H in case of I/O error during DO processing.
4416H ↳17430		L1, M1	Change entry address of task in interrupt chain. D3: Remove task from interrupt chain. N1, N3: Keep drives rotating and reselect current drive.
4417H ↳17431		L3	Contains current day in coded format.
4419H ↳17433		T3, L3	Write 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		T3, L1, L3, D1, D3, N1, N3, M1, M3	Move filespec to FCB.
441FH ↳17439		Model 3 Disk	OSVER$: Holds the DOS Version Number. Stored in DCB format. Note on a M1 this is stored in 403EH and on the M4 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		All	Open or create a file.
4424H ↳17444		All	OPEN 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		All	CLOSE: 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		All	KILL: 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		T3	DUAL/ROUTE Flag. 80H=ROUTE is ACTIVE, FFH=DUAL is ACTIVE, 00H=Neither is active.
4430H ↳17456		All	(undocumented in T1) Load and Execute a Model I Program into Memory. Call be used with CALL 4430H.
4433H ↳17459		All	(undocumented in T1) Load and Execute a Model I Program. Can be used with JP 4433H.
4436H ↳17462		All	Read 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		All	Write 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		All	Write record and verify.
443FH ↳17471		T3, L1, L3, D1, D3, N1, N3, M1, M3	Point 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		All	Position file to specified record.
4445H ↳17477		T3, L1, L3, D1, D3, N1, N3, M1, M3	Backspace file one record.
4448H ↳17480		T3, L1, L3, D1, D3, N1, N3, M1, M3	Position to end of file.
444BH ↳17483		T3, L3, D3, M3	Add extension to filespec in FCB (see also 4473). L1: Check for end of file. D1: Multiply 16 bit by 8 bit integer. N1, N3: Allocate disk space to file.
444DH ↳17486		Model III	[This is the start of RAM for a Model III as far as the memory test goes].
444EH ↳17486		T3, L3, D3	Multiply 16 bit by 8 bit integer. L1: Update directory with current record as end of file. D1: Divide 16 bit by 8 bit integer. N1, N3: Position file to specified byte record.
4451H ↳17489		T3, L3, D3	Divide 16 bit by 8 bit integer. D1: Check for end of file. N1, N3: Update directory with record as end of file.
4454H ↳17492		L1	Read current sector. L3, D3, M3: Parse parameters in command line. D1: Find drive and file number of a file.
4457H ↳17495		L1	Rewrite current sector. D3: Check for end of file. D1: Read directory to user buffer.
4458H ↳17496		L3	Check for end of file.
445AH ↳17498		L1	Calculate current logical record number. D1, D3: Display directory on CRT.
445BH ↳17499		L3	Update directory with current record as end of file. N1, N3: Select and power up specified drive.
445DH ↳17501		L1	Calculate EOF record number.
445EH ↳17502		L3	Reread current sector. N1, N3: Test drive and disk.
4460H ↳17504		L1	Skip next logical record.
4461H ↳17505		L3	Rewrite current sector. N1, N3: Add user routine to DOS library chain.
4462H ↳17506		D1, D3	Send text to printer.
4463H ↳17507		L1	Read directory to buffer or CRT.
4464H ↳17508		L3	Skip next logical record. N1, N3: Remove user routine from DOS library chain.
4467H ↳17511		L1, L3, D1, D3, N1, N3, M1, M3	Display text on CRT.
446AH ↳17514		L1, L3, N1, N3, M1, M3	Send 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		T1, L1, D1, D3, N1, N3, M1	Get 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		L3	Calculate end of file record number.
4473H ↳17523		L3	Holds image of interrupt latch. T1, L1, D1, D3, N1, N3, M1, M3: Add default extension to filespec in FCB. (See also 444BH)
4476H ↳17526		L1, D1, M1, M3	Parse parameters in command line.
4478H ↳17528			NewDOS/80 v2.0 for Model 3 Break Vector (195=Off, 201=On).
4478H ↳17528		1	MODEL 3 NEWDOS/80 V2.0 BREAK VECTOR ↳ 195=OFF, 201=ON
447BH ↳17531		L1	Send text to job log and CRT. N3: Add task interrupt chain.
447CH ↳17532		D1, D3	Compare filespec to wildcard mask.
447EH ↳17534		L1	Send text to joblog.
447FH ↳17535		D1, D3	Get device number for file or I/O device.
4480H ↳17536		T1	System DCB Address for TRSDOS v2.3
4482H ↳17538		D1, D3	Sort block of memory.
4485H ↳17541		D1	10 disk I/O functions depending on value in A.
4488H ↳17544		D3	10 disk I/O functions depending on value in A. D1: Locate device control block for any device.
448BH ↳17547		D1	Locate drive control table for any drive.
44A0H ↳17568		D3	Locate device control block for any device.
44A3H ↳17571		D3	Locate drive control table for any drive.
44B8H ↳17592		L1	Check drive and disk.
44BBH ↳17595		L1	Get file name from directory.
44C1H ↳17601		L1	Multiply 16 bit by 8 bit integer.
44C4H ↳17604		L1	Divide 16 bit by 8 bit integer.
44D2H ↳17618		M3	Add task to interrupt chain.
44D5H ↳17621		M3	Remove task from interrupt chain.
44D8H ↳17624		M3	Change execution address of task in interrupt chain.
44DBH ↳17627		M3	Set task pointer to default of RET.
44DEH ↳17630		M1, M3	Verify a sector without reading to RAM.
44E1H ↳17633		M1, M3	Read sector.
44E4H ↳17636		M1, M3	Write sector.
44E8H ↳17640		M1, M3	Read directory sector.
44EBH ↳17643		M1, M3	Write directory sector.
44EEH ↳17646		M1, M3	Read director.
44F1H ↳17649		M1, M3	Write directory.
44F4H ↳17652		M1, M3	User function.
44F7H ↳17655		M1, M3	Get directory track number.
4500H-4517H ↳17664-17687		Level 2	DOS interrupt table contains address pairs for interrupt routines (ie. 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 rtn EI ;enable interrupts
45F8H ↳17912		T3	Part 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 selcted, 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, L3	Select drive.
4759H ↳18265		L1, L3	Continually reselect drive until it is ready.
475EH ↳18270		L1, L3	Seek specified cylinder (track).
4763H ↳18275		L1, L3	Write sector to disk.
4768H ↳18280		L1, L3	Write system (directory) sector.
476DH ↳18285		L1, L3	Write track to disk (used for formatting).
4772H ↳18290		L1, L3	Verify sector without transfering data to memory.
4777H ↳18295		L1, L3	Read sector to buffer.
4779H ↳17529		L1	Send text to file or device. D1, D3: Scan and evaluate command line.
478FH ↳18319		L1, L3	Get address of drive code table for specifed drive.
479CH ↳18332		L1, L3	Get 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 overlayed by BASIC/CMD. ( not for Newdos 80). To Use: LD B,0 LD DE,BUFFER ;256*8 bytds read CALL 4AC1H ;read sector LD L,0 PUSH BC LD BB,256 LDIR POP BC INC B LD A,B CP 8 JR NZ,read RET
4B10H ↳19216		L1, L3	Read directory sector with specified entry code.
4B1FH ↳19231		L1, L3	Write system buffer to specified directory sector.
4B45H ↳19269		L1, L3	Read directory sector to user buffer.
4B64H ↳19300		L3	Get cylinder (track) number of directory.
4B65H ↳19301		L1	Get cylinder (track) number of directory.
4B6BH ↳19307		L3	Multiply 8 bit by 8 bit integers.
4B6CH ↳19308		L1	Multiply 8 bit by 8 bit integers.
4B7AH ↳19322		L3	Divide 8 bit by 8 bit integers.
4B7BH ↳19323		L1	Divide 8 bit by 8 bit integers.
4CE7H ↳19687		T3	Storage Location for Video Driver. Used when involking DUAL.
4CF8H ↳19688		T3	Storage Location for Printer Driver. Used when involking DUAL.
4D00H-4DFFH ↳19712-19967		T1	BOOT/SYS Resides Here in Memory
4E00H-50A7H ↳19968-20647		T1	SYS1/SYS Resides Here in Memory
4FFFH 20479		M1, M3	4K System Top of Memory
5200H-6FFFH 20992-28671		Level 2	Disk BASIC or DOS utilities when loaded, or user memory
5203H	ERRTAB	T1	TRSDOS BASIC Extended Error Messages. These get used instead of the L2 built-in messages.
54C3H	54C3H	T1	DOS Vector – CVI Command
57F0H 22512		Level 2	61 character ASCII copyright notice (DOS)
582CH	SCRMBL	T1	The copyright message “THIS BASIC WAS AUTHORED AND IS COPYRIGHTED BY MICROSOFT, 1978”
586BH	PROTMS	T1	The message “PROTECTION HAS CLEARED MEMORY”
5A77H	DIRTMP	T1	The status of FILE 0 (open or closed) in TRSDOS v2.3 BASIC
5B77H	USRTAB	T1	The start of the USR(0)…USR(15) Jump Table
5B8BH	MAXTRK	T1	A Byte which toggles whether the command being processed was a GET or a PUT
5B8CH	DSKERR	T1	Storage location for the DOS error code
5B8DH-5B8EH	PTRFIL		The address in RAM of the file being used
5B8FH	FILPTR	T1	Start of the File Block Pointer Table for Files 01 to 15 (i.e., OPEN “I”,n,”FILENAME”)
5BAFH	FILPT1	T1	Copy of the FLIPTR for File 0
5BB1H	LSTFRE	T1	A flag as to whether to run a BASIC program or not once the current operation is done
5C98H	PTCMD	T1	A flag to see if TRSDOS v2.3 was restarted or cold booted
5C99H	SVTXTT	T1	BASIC Program Beginning Pointer
5C9BH	FILSVS	T1	The answer to the FILES? question enterd by the user when entering BASIC
5C9DH	OLSTTP	T1	Pointer to the lowest address available for string storage a/k/a top of free memory
5D51H	NXTFCN+1	T1	Exit JUMP Address Storage location for a CMD”S” or CMD”A” return to DOS from BASIC
5E57H	BADMVS	T1	Pointer to the message “USE TRSDOS 2.2 OR LATER”
5E70H	FILMES	T1	Pointer to the message “HOW MANY FILES”
5E7FH	MESG	T1	Pointer to the message “RADIO SHACK DISK BASIC VERSION 2.2”
5EA3H	FILNAM	T1	32 character buffer to store the current filename
651EH	FLRL	T1	Storage for the record size used in a FIELD command
651FH	DOPROT	T1	Flag as to whether an action is permitted based on the protection level of the file in the directory
6520H	PROTFL	T1	A different format of the protection level flag for the current file
6574H	DERTAB-1	T1	The byte before the table of DOS specific error message table that yses SYS4 to process the error instead of BASIC
6575H	DERTAB	T1	Table of DOS specific error message table that yses SYS4 to process the error instead of BASIC
68D9H-26841		3	RAM – BASIC PROGRAM IN TRS-DOS 1.3
7A00H 32767		3	Network 4 Read Buffer
7FFFH 32767		1/3	16K SYSTEM TOP OF PHYSICAL MEMORY
BFFFH 49151		3	32K System Top of Memory
FFFFH 65535		3	48K System Top of Memory

RAM Addresses and Routines for Level 1:

Address (Hex/Dec)	Official Symbol	Model Code	Description
3C00 ↳ 15360		L1	Start of screen memory
3FFF ↳ 16383		L1	End of screen memory
4000 ↳ 16384		L1	A value
4004 ↳ 16388		L1	B value
4008 ↳ 16392		L1	C value
400C ↳ 16396		L1	D value
4010 ↳ 16400		L1	E value
4014 ↳ 16404		L1	F value
4018 ↳ 16408		L1	G value
401C ↳ 16412		L1	H value
4020 ↳ 16416		L1	I value
4024 ↳ 16320		L1	J value
4028 ↳ 16324		L1	K value
402C ↳ 16328		L1	L value
4030 ↳ 16332		L1	M value
4034 ↳ 16336		L1	N value
4038 ↳ 16340		L1	O value
403C ↳ 16344		L1	P value
4040 ↳ 16348		L1	Q value
4044 ↳ 16352		L1	R value
4048 ↳ 16356		L1	S value
404C ↳ 16360		L1	T value
4050 ↳ 16464		L1	U value
4054 ↳ 16468		L1	V value
4058 ↳ 16472		L1	W value
405C ↳ 16476		L1	X value
4060 ↳ 16480		L1	Y value
4064 ↳ 16484		L1	Z value
4068 ↳ 16488		L1	Pointer to cursor position
406A ↳ 16490		L1	Points to top of physical memory
406C ↳ 16492		L1	Pointer to top of used memory
406E ↳ 16494		L1	Current FOR end value
4070 ↳ 16496		L1	A$ Value (16 bytes)
4080 ↳ 16512		L1	B$ Value (16 bytes)
4090 ↳ 16528		L1	Cassette port status cache (byte)
4091 ↳ 16529		L1	Current FOR step value
4093 ↳ 16531		L1	pointer to top of current FOR statement
4095 ↳ 16533		L1	pointer to current FOR statemnt?
4097 ↳ 16535		L1	Save for pointer to current line
4099 ↳ 16537		L1	pointer to print buffer
409B ↳ 16539		L1	pointer to NEXT variable
409D ↳ 16541		L1	Parse pointer saved at a STOP
409F ↳ 16543		L1	pointer to current line being executed
40A1 ↳ 16545		L1	READ pointer
40A3 ↳ 16547		L1	Saved SP for this BASIC frame
40A5 ↳ 16549		L1	pointer to current FOR variable
40A7 ↳ 16551		L1	Three bytes of RNG state
40AA ↳ 16554		L1	??
40AC ↳ 16556		L1	Buffer for command input, print output to cassette
40F3 ↳ 16627		L1	End of buffer
40F4 ↳ 16628		L1	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)
4180 ↳ 16768		L1	Bottom of system stack pointer
4200 ↳ 16896		L1	Top of system stack pointer
4201 ↳ 16897		L1	Start of BASIC Program Storage. 16 bit line number followed by line text, terminated with a 0DH