Web site: (not active)
Origin: USA
Category: Desktop
Desktop environment: CLI
Architecture: Zilog Z-80
Based on: independent
Wikipedia: TRSDOS
Media: install
The last version | Released: 6.3 | 1987
TRSDOS (Tandy Radio Shack Disk Operating System) – a disk operating system offered for the TRS-80 line of home computers manufactured by Tandy Corporation and sold by Radio Shack in the late 1970s and early 1980s.
TRSDOS consisted of a command-line interface and DISK BASIC, an extension of BASIC built into the computer’s ROM that was used to control external disk drives, since BASIC only supported magnetic tape drives. These units could be connected to the computer via an Expansion Interface, an expansion interface that also integrated a Western Digital 1771 controller. The floppy disks that could be managed by the 1771 were 5.25″ single density, that is, with 89 kB of capacity (later double density, 160 kB).
Although TRSDOS was offered by Radio Shack together with the expansion interface, the bugs present in the first versions convinced many users to adopt other commercial DOS such as NEWDOS/80, LS-DOS and VTOS, the latter marketed by the same creator of TRSDOS, Randy Cook.
The first version of TRSDOS for the TRS-80 Model I was version 2.0, dated July 7, 1978. By Cook’s own admission, given the numerous bugs it contained, it should never have been released.
Many of these bugs were corrected in version 2.1, released in September of the same year. In an attempt to correct these bugs, several manufacturers began selling their own corrected versions of TRSDOS 2.1: this is how alternative DOS to TRSDOS were born, such as DOSPLUS, ULTRADOS and NEWDOS.
In 1979, version 2.2 was released, which corrected almost all the bugs of the previous 2.1. In this version, Cook also left his digital “signature” inside TRSDOS, which can be viewed by entering a certain command.
Shortly after the previous one, version 2.3 was released. Compared to 2.2, only the hidden message inserted by Cook changed, which Tandy had replaced with his own copyright notice.
In 1982, version 2.7 was released: it was not an update of the previous 2.3, but a completely new system, derived from the TRSDOS developed for the new TRS-80 Model III. The real novelty was the support for the new double-density disks, something that competing DOS had introduced well before it.
The same year, TRSDOS 2.8 was also released, which corrected a bug that affected the copying of disks when there was only one disk drive.
In 1980 Tandy produced the TRS-80 Model III, the successor to the first TRS-80, renamed Model I. Unlike the latter, the floppy disk drive was standard, so the computer was offered with DOS from the beginning. The TRSDOS offered with the Model III, however, had nothing to do with that of the Model I, being a rewritten operating system inspired by TRSDOS-II, the system that equipped the TRS-80 Model II introduced in 1979 as an office machine. For this reason, the numbering of the system also changed: the first release was TRSDOS Model III 1.0, the last version was 1.3 on May 1, 1981.
TRSDOS 6 shipped with the TRS-80 Model 4 in 1983 is identical to LDOS 6.00.
