Model I TRSDOS Disk BASIC Commands

written by Matthew Reed

Model I TRSDOS Disk BASIC contained a number of extra commands and enhancements to Level II BASIC, not all related to disk. The commands were documented in the TRSDOS 2.3 Reference Manual. All other TRS‑80 operating systems with a Disk BASIC supported these commands, although often CMD and NAME used different syntax.

Language Enhancements

These extra BASIC commands had nothing to do with disk, but were useful enhancements. All of the commands were built on hooks in the Level II BASIC ROM reserved for future use by Level III BASIC. This explains the ?L3 ERROR you receive if you attempt to invoke them from cassette BASIC.

&H hexadecimal constant prefix
&O octal constant prefix
CMD “D” enable and load the debugger
CMD “I” return a command to TRSDOS
CMD “R” enable interrupts
CMD “S” return normally to TRSDOS
CMD “T” disable interrupts
DEF FN define an implicit BASIC statement function
DEF USRn define the entry point for an external machine-language routine (n=0 to 9)
INSTR find substring in source string
LINE INPUT input a line from the keyboard
MID$= replace portion of target string
NAME renumber a program (BASICR only)
TIME$ get date and time
USRn call external routine (n = 0 to 9, previously defined with DEF USR)

File manipulation

These commands were used for loading and saving BASIC program files.

KILL “filename” delete a program or data file from the disk
LOAD “program” load a BASIC program from disk
MERGE “program” merge an ASCII BASIC program on disk with the program in memory
RUN “program” load and execute a BASIC program stored on disk
SAVE “program” save the BASIC program in memory onto disk

File access

These commands could read from and write to disk files, providing both sequential and random access.

OPEN open a file for access
CLOSE close an open file
INPUT# read from disk (sequential mode)
LINE INPUT# read a line of data from disk (sequential mode)
PRINT# write to disk (sequential mode)
GET read from disk (random access mode)
PUT write to disk (random access mode)
FIELD assign field names and sizes to a random access file buffer
LSET place value in specified buffer, right padded with spaces
RSET place value in specified buffer, left padded with spaces
CVD restore double-precision number to numeric form after GET from disk
CVI restore integer number to numeric form after GET from disk
CVS restore single-precision number to numeric form after GET from disk
EOF determine if end-of-file encountered
LOF return number of last record in file
MKD$ convert double-precision number to string before it is PUT to disk
MKI$ convert integer number to string before it is PUT to disk
MKS$ convert single-precision number to string before it is PUT to disk


Dirk Martin says:

Ah…these were the good ‘ol days.
Still got my Model I and Model III.
Both work fine.

Leave a Comment

All comments are moderated. The name and email fields are required, but your email address will not be published.

Thank you for commenting!