Articles in the "Operating Systems" Category

TRSDOS for the Model III

Model III TRSDOS, better known as TRSDOS 1.3, was Radio Shack’s official disk operating system for the TRS-80 Model III. It was available either bundled with a disk-based Model III, as part of Radio Shack’s floppy disk upgrade, or purchased as a separate product (catalog number 26-0312) for $14.95. Almost everyone who had a disk-based Model III had a copy of Model III TRSDOS.

Unlike Model I TRSDOS, which was written under contract by Randy Cook, Model III TRSDOS was developed in-house by Radio Shack. It was at least partially based on Model II TRSDOS, and shares many of the same commands. Here is a description from a 1981 Radio Shack catalog:

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The Kill Command

The KILL command was probably the most unusually named command in the TRSDOS disk operating systems for TRS-80 computers. KILL was used to delete a file, for example: KILL FILENAME/EXT.

The KILL command was supported by versions of TRSDOS for the Model I, Model III, and Model II, as well as the BASIC interpreters for all those machines plus the Model 4, Color Computer, the Model 100, Model 102, Model 200, and the Model 2000. In addition, all of the TRSDOS-compatible TRS-80 Model I/III operating systems (NEWDOS, MULTIDOS, DOSPLUS, and LDOS) also implemented the KILL command.

The use of KILL as a command was somewhat controversial and many people objected to the connotation. Here’s what Josef Friedman said about KILL in his article “Thou Shalt Not Kill” in the November 1984 issue of 80 Micro:

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NEWDOS 2.1, also known as NEWDOS, NEWDOS/21, and NEWDOS+, was the first alternative disk operating system for the TRS-80 Model I. Introduced in March 1979 by Apparat, Inc. of Denver, Colorado, NEWDOS jump started the entire third-party TRS-80 disk operating system market. NEWDOS was considered by many to be an essential program for the Model I; it is quite possible that NEWDOS was more widely used than Model I TRSDOS itself.

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MULTIDOS was one of the major TRS-80 operating systems, described in advertisements as “the most compatible, user friendly operating system on the market.” It was written by Vernon Hester, the author of ULTRADOS, and was in some ways a continuation of that operating system. MULTIDOS was the least expensive TRS-80 operating system and also the one with the most recent update (MULTIDOS 5.1 in 2005). It was also the only TRS-80 operating system to offer software compatible versions for the TRS-80 Model I, Model III, Model 4, and the Lobo MAX-80.

ULTRADOS was an earlier TRS-80 operating system for the Model I that was sold by Level IV Products. After Vernon Hester parted ways with Level IV Products in 1981, he began writing a completely new operating system. This operating system, which was briefly advertised as ULTRA-II, soon became known as MULTIDOS. Vernon Hester originally sold MULTIDOS through his company, Cosmopolitan Electronics Corporation. The Model I version of MULTIDOS was released in late 1981 and the Model III version was released in January 1982. The price started out at $79.95 but soon increased to $99.95. Later on, MAX-80 MULTIDOS was released in late 1983 and Model 4 MULTIDOS (originally known as MULTIDOS 80/64) in 1985.

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DOSPLUS was one of the most popular of the disk operating systems available for the TRS-80. Sold by Micro-Systems Software based in Hollywood (later Boca Raton), Florida, there were eventually versions of DOSPLUS for the TRS-80 Model I, Model III, Model II, and Model 4.

The people behind Micro-Systems Software were Larry Studdard, Mark Lautenschlager, Steve Pagliarulo, and later Todd Tolhurst. According to a 1981 interview in 80-U.S. Journal, DOSPLUS came about indirectly when they were writing software for Larry Studdard’s sheet metal business. Steve Pagliarulo developed a number of patches to TRSDOS to deal with bugs they had encountered. That experience led Pagliarulo to write his own TRSDOS-compatible replacement operating system, which became the first version of DOSPLUS. That original version was never publicly released and was used only with their business software.

In 1980, Micro-Systems Software introduced DOSPLUS 3.0, the first publicly available version of DOSPLUS, for $99.95. The name “DOSPLUS” presumably identified it as an improvement to the Radio Shack DOS or as “DOS Plus.” Although not actually the third version, it used a 3.0 version number to show that it followed TRSDOS 2.3. Advertisements described it as “the fastest, most reliable, and easy-to-use operating system available.”

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VTOS (which stood for “Virtual Technology’s Operating System”) was the second TRS-80 Model I operating system created by Randy Cook, the author of Model I TRSDOS. VTOS was released in 1979 and sold through Randy Cook’s company, Virtual Technology Inc. The original price was $49.95 for VTOS version 3.0. That was increased to $99.95 for version 4.0, or $125.00 for VTOS plus Operator’s Guide and Master Reference manual. There doesn’t appear to have been a Model III version of VTOS.

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ULTRADOS was the first TRS-80 operating system written by Vernon Hester. Introduced in September 1980, ULTRADOS was sold by Level IV Products, a software and hardware retailer based in Michigan. The regular price for ULTRADOS was $119.95 but the introductory price of $89.95 lasted for several months. ULTRADOS was for the Model I only; there never was a Model III version.

Originally called Level IV DOS, ULTRADOS began life as a heavily patched version of Model I TRSDOS. However, Vernon Hester made so many modifications that ULTRADOS bore little resemblance to TRSDOS. ULTRADOS was a very stable operating system with the bugs of TRSDOS corrected.

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MICRODOS, later known as OS-80, was the only TRS-80 disk operating system that made no attempt at TRSDOS compatibility. It was written by James W. Stutsman and released by Percom in 1979. Rather than using a command shell like Model I TRSDOS, MICRODOS used extensions to BASIC. It implemented most of the Disk BASIC commands added by TRSDOS. Also unlike the other operating systems, MICRODOS had no file system. All disk accesses were made using the starting sector and length. As stated in the manual:

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Model I TRSDOS Versions

TRSDOS 2.0 was the first version of Model I TRSDOS to be released to the public. All earlier versions had been used for testing within Radio Shack only. It came with a preliminary instruction manual, with a final manual promised for the near future. Not many people used TRSDOS 2.0 because it was replaced by TRSDOS 2.1 after only a short time.

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Model I TRSDOS Disk BASIC Commands

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.

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