TRSDOS (which stands for the Tandy Radio Shack Disk Operating System) is the
operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
for the
Tandy TRS-80 line of eight-bit
Zilog Z80
The Z80 is an 8-bit computing, 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first wor ...
microcomputers that were sold through
Radio Shack from 1977 through 1991. Tandy's manuals recommended that it be pronounced ''triss-doss''. TRSDOS should not be confused with Tandy DOS, a version of
MS-DOS
MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few oper ...
licensed from
Microsoft
Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation producing Software, computer software, consumer electronics, personal computers, and related services headquartered at th ...
for Tandy's
x86 line of
personal computer
A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or tech ...
s (PCs).
With the original TRS-80 Model I of 1977, TRSDOS was primarily a way of extending the MBASIC (
BASIC
BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
in
ROM) with additional
I/O (input/output) commands that worked with disk files rather than the cassette tapes that were used by non-disk Model I systems. Later disk-equipped
Model III computers used a completely different version of TRSDOS by Radio Shack which culminated in 1981 with TRSDOS Version 1.3. From 1983 disk-equipped
TRS-80 Model 4 computers used TRSDOS Version 6, which was a development of Model III LDOS by Logical Systems, Inc. This last was updated in 1987 and released as LS-DOS 6.3.
C