By itself, the TRS-80 Model I was capable of only limited expansion. In order to add memory beyond 16K and support floppy disk drives, Radio Shack sold an external device they called an Expansion Interface.
The Expansion Interface could expand memory to 48K, add a parallel printer port, and add a disk controller for connecting floppy disk drives. But an Expansion Interface with 32K of memory cost $597.00, almost $100 more than a 4K Model I. What if a Model I owner didn’t want (or couldn’t afford) disk drives but still wanted to add memory and a printer port?
The MT-32 from Microtek, Inc. of San Diego, California used a different approach from the Radio Shack Expansion Interface. The MT-32, introduced in mid-1980, offered only two features: the ability to add 32K of RAM (for a total of 48K) and a parallel printer port.
There were many books written that described and in some cases disassembled the TRS-80 Model I BASIC ROM. A few of the more famous examples were Microsoft BASIC Decoded and Other Mysteries from IJG, Inc., The B00K from Insiders Software Consultants, Pathways Through the ROM from SoftSide Publications, and Level II ROMs from Tab Books. But there were far fewer books serving the same purpose for the TRS-80 Model III BASIC ROM.
One of the best sources of information about the Model III ROM was TRS‑80 ROM Routines Documented by Jack Decker, which was published in 1983. But probably the best known was MOD III ROM Commented from Soft Sector Marketing. MOD III ROM Commented was published in 1981 with two printings. It contains a very detailed disassembly of the Model III BASIC ROM. As the book cover promised: “Not a rehash of old information, but an explanation of ROMS in the latest machine from Tandy.”
When the TRS-80 Model I was introduced on August 3, 1977, it came with Level I BASIC, a 4K BASIC interpreter, in ROM. Level I BASIC was created by Steve Leininger, the designer of the TRS-80, who based it on the public domain “Palo Alto Tiny BASIC” that Dr. Li-Chen Wang wrote in 1976.
But Radio Shack’s plan was always to upgrade to a more advanced Model I BASIC later. The very first TRS-80 brochure said that “planned expansion includes an extended Radio Shack Level II BASIC.” It was mentioned again in the first issue of the TRS-80 Microcomputer News (then known as the Radio Shack Microcomputer Newsletter) in 1977:
A Level II BASIC is now being developed. This will be a 12K BASIC with every feature you ever imagined – PEEK and POKE, PRINT USING, transcendental functions, advanced string handling, etc. It should be available on ROM soon.
The Aerocomp DDC was a popular double-density add-on for the TRS-80 Model I. It was introduced in 1981 by Aerocomp Inc. of Dallas, Texas, a company founded by John Lancione. Aerocomp was one of the longest lasting TRS-80 companies and the Aerocomp DDC was sold for almost a decade.
When it was introduced, the Aerocomp DDC cost $149.95. This was $20 cheaper than its primary competitor, the Percom Doubler II. Aerocomp also sold the Aerocomp DDC bundled with a choice of operating systems: DOSPLUS 3.3 for $189.95 and with LDOS for $239.95.
The Percom Doubler was the original Model I doubler and the Aerocomp DDC was designed to be software compatible with it. The Aerocomp DDC (like the Percom Doubler) used double-density encoding to increase disk capacity on a 40-track single-sided disk from 100K to 180K
The Freedom Option was a CP/M add-on for the TRS-80 Model I, Model III, and compatibles. It was introduced in early 1980 by Field Engineering Consultants (better known as FEC) of Woburn, Massachusetts.
Originally, FEC sold two Freedom boards, both for a 48K Model I with disk drives:
- The Freedom Option allowed CP/M (or the included T8/OS) to run by disabling the Model I ROM. It cost $245.00.
- The Memory Expansion Option had the same features as the Freedom Option, but also added an extra 16K of RAM. This provided a full 64K of RAM for the Model I, meaning that 57K was available for programs when running T8/OS. It cost $295.00.
Both the Freedom Option and the Memory Expansion Options were fairly small boards that installed inside the Model I case. As one advertisement stated they were “easy to install plug-in boards; no wires or traces to cut; no soldering.”
Most people considered the Big Five Software games to be the finest games ever written for the TRS-80 Model I and III. They were sold directly through Big Five Software and were resold by many other companies.
Radio Shack also sold Big Five Software games in two collections compiled by Cogito Software. Games Pack Two and Games Pack Three first appeared in the 1984 Radio Shack catalog and contained four Big Five games: Defense Command, Stellar Escort, Cosmic Fighter and Meteor Mission 2. As the packaging stated: “You can look forward to hours of fun for the family, friends, or even the gang at the office.”
Both collections were sold on cassette and self-booting disk. Only minor modifications were made to the games, the biggest being that all copyright messages were changed to “Licensed to Tandy Corporation.
Word processing was one of the most important applications for early microcomputers. WordStar, introduced in 1979 by MicroPro International, became the best selling word processor soon after it was introduced. According to the market research firm InfoCorp, WordStar was the most popular word processor in 1984 with 24% of the worldwide market.
MicroPro sold versions of WordStar for CP/M (including Apple II CP/M) and MS-DOS. Many people bought a CP/M add-on for the TRS-80, such as the Omikron Mapper, just to run WordStar.
WordStar was written by John Robbins Barnaby (usually referred to as Rob Barnaby) with assistance from Jim Fox. MicroPro began shipping the first version of WordStar in mid-1979.
Here is the announcement from a MicroPro advertisement introducing WordStar (then billed as WORD-STAR) in the April 1979 issue of BYTE:
The Interstellar Drive, also known as Pion’s Interstellar Drive, was a solid state disk drive emulator that was sold by Pion, Inc. of Arlington (later Watertown), Massachusetts. It was introduced in 1982 for a base price of $1,095.00 for the 256K version.
The Interstellar Drive was an external 9" by 8 1/2" by 4" unit with its own power supply. It was compatible with the TRS-80 Model III and Model 4 and included drivers for the TRSDOS and LDOS disk operating systems. By using different host interfaces, the Interstellar Drive was compatible with a number of computers, including the Apple II and the IBM PC.
Much like a modern solid state drive, the Interstellar Drive had no moving parts. It provided non-volatile data storage at speeds far greater than a hard drive (then commonly known as a Winchester drive) or a floppy drive. Advertisements described the Interstellar Drive as providing “five to fifty times faster performance than floppy disks and Winchester drives.”
The FPS-3 was an unusual hardware add-on for the TRS-80 Model III and Model 4 that gave users the ability to make backup copies of their copy protected TRS-80 programs. It was created by Steve Sawyer and sold for $50.00 through his company J.E.S. Graphics of Tulsa, Oklahoma.
Most products that could defeat TRS-80 copy protection, such as Super Utility or Trackcess, were software that used the TRS-80 hardware to make exact copies of protected disks or tapes. This didn’t always work depending on the type of protection used. The most notable example was Super Utility, which couldn’t be used to make copies of itself!
Rather than use this approach, the FPS-3 was hardware that made copies of the data that a protected program loaded from disk or tape. It could create an exact snapshot of a program immediately after it had loaded into memory. As long as the protected program loaded completely from disk or tape with no overlays (as most did), the FPS-3 could be used to create an unprotected copy.
The TRS-80 Applications Software Sourcebook, also known as the Applications Sourcebook, was a book containing short descriptions and information about third-party application software for the TRS-80. It was published by Radio Shack with at least eight volumes from 1980 to 1987.
Any publisher could buy a listing in the TRS-80 Applications Software Sourcebook. A listing cost $10.00 and included the name of the program, the price, a short description, TRS-80 compatibility information, and ordering details. A listing could only mention one program and there were no discounts for multiple listings.
Radio Shack first announced the TRS-80 Applications Software Sourcebook in the March/April 1980 issue of the TRS-80 Microcomputer News: