TRS-DOS was the Disk Operating System for the Tandy TRS-80 line of 8-bit Z-80 micro-computers that were sold through Radio Shack through the late 1970s and early 1980s. Their own manuals recommended that it be pronounced triss-doss but the common vernacular referred to the platform as trash-eighties and thus this software was usually called trash-dos.

TRS-DOS was primarily a way of extending the MBASIC (BASIC in ROM) with additional I/O (input/output) commands that worked with disk files rather than the cassette tapes that were used by most other TRS-80 systems.

TRS-DOS supported up to four floppy (mini-diskette) drives which used 5 1/4" (five and one quarter inch) diskettes with a capacity of 160K (kilobytes) each. The drives were numbered 0 through 3 and the system diskettes (which contained the TRS-DOS code and utilities) had to be in drive 0.

Some typical TRS-DOS utilities (commands):

Notes:

• Since TRS-DOS didn't have the notion of redirection as UNIX/Linux and MS-DOS do, the APPEND command is somewhat different in concept than the UNIX or MS-DOS notion of appending via output redirection.
• The CLOCK command display a real time clock in the upper corner of the display, almost like a DOS TSR (terminate and stay resident); no exactly corresponding feature exists in MS-DOS or UNIX, though many programs provided similar features for DOS and the common UNIX shells could embed the time into their user defined "prompt string"
• I don't remember MS-DOS tape handling commands; UNIX never interfaced to audio cassettes like the TRS-80 but the dd command is similar in concept
• program invocation under DOS and UNIX is done by filename; no explicit LOAD command is required for normal binary executables nor for text command files (.BAT files in DOS and shell scripts in UNIX/Linux).
• Under DOS and UNIX printing a file can be done with redirection; under UNIX it's normally done by spooling the file to the "line printer" (using the lpr command) because UNIX is conventionally a multi-user system.
• ATTRIB, PROT, and the chmod UNIX command are all somewhat different in their semantics. UNIX/Linux is multi-user and each user can control read, write, and execute permissions on his or her own files and directories. MS-DOS is single user and the file attributes for "read-only," "hidden," and "system" are advisory in nature. TRS-DOS was single user but supported some sort of on disk password protection for specific files.
• The AUTO coomand set an automatic command to be executed on TRS-DOS boot; under MSDOS the special, reserved file named AUTOEXEC.BAT contained a list of such commands. On UNIX a set of one or more rc files under /etc/ are a set of boot time "run commands" and special "dot files" in a user's home directory are run for each time that a given user logs into the system. UNIX supports many other "dotfiles" for many of its commands which are akin to the Macintosh "preferences" folder contents.

Although MS-DOS owes its heritage most closely to CP/M and thence to TOPS-10, it should be obvious that many of the file manipulation commands are very similar to those of TRS-DOS. By comparison the CP/M command for copying files was called pip (both a pun on the Pip printers, a chain of copy centers in that era; and standing for "peripheral interface to peripheral").

CLOAD"FILENAME" is the format for loading tape programs on a TRS-80.

Dates

• May 8, 1979 - Radio Shack releases TRSDOS 2.3
• May 1, 1981 - Radio Shack releases Model III TRSDOS 1.3

External links

• Mike's Virtual Computer Museum: TRS-80
• TRS-80 Error Messages
• TRS-80 Revived Software Collection (good pictures of a Model IV)
• Model III Home Page (with list of TRS-DOS alternatives on the TRS-80 Model III
• Matthew K. Reed's TRS-80 Emulator Software Runs under MS-DOS; requires the extraction of a ROM image
• xtrs A TRS-80 emulator for UNIX and X Windows; similar ROM issues apply
• TRSdisk - TRS-DOS utilities for UNIX
• TRS-DOS Documentation Preservation Page (Warning links not working :( )
• TRS-DOS Applications