TRS-80
The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their Radio Shack stores. The name is an abbreviation of Tandy Radio Shack, Z80 [microprocessor].[4] It is one of the earliest mass-produced and mass-marketed retail home computers.[5]
This article is about the original TRS-80 (Model I) and its successors (Models III and 4). For an overview of all computers using the TRS-80 and Tandy names, see List of TRS-80 and Tandy-branded computers. For other uses, see TRS-80 (disambiguation).Manufacturer
August 3, 1977[1]
1977–1981, 4 years
US$599.95 (equivalent to $3,020 in 2023)
January 1981
4–48 KB
Monochrome 12" CRT, 64 × 16 character semigraphics
Square wave tones
The TRS-80 has a full-stroke QWERTY keyboard, the Zilog Z80 processor, 4 KB dynamic random-access memory (DRAM) standard memory, small size and desk area, floating-point Level I BASIC language interpreter in read-only memory (ROM), 64-character-per-line video monitor, and a starting price of US$600[1] (equivalent to US$3,000 in 2023). A cassette tape drive for program storage was included in the original package.
While the software environment was stable, the cassette load/save process combined with keyboard bounce issues and a troublesome Expansion Interface contributed to the Model I's reputation as not well-suited for serious use. Initially (until 1981), it lacked support for lowercase characters which may have hampered business adoption.
An extensive line of upgrades and add-on hardware peripherals for the TRS-80 was developed and marketed by Tandy/Radio Shack. The basic system can be expanded with up to 48 KB of RAM (in 16 KB increments), and up to four floppy disk drives and/or hard disk drives. Tandy/Radio Shack provided full-service support including upgrade, repair, and training services in their thousands of stores worldwide.
By 1979, the TRS-80 had the largest selection of software in the microcomputer market.[6] Until 1982, the TRS-80 was the bestselling PC line, outselling the Apple II series by a factor of five according to one analysis.[4]
The broadly compatible TRS-80 Model III was released in the middle of 1980. The Model I was discontinued shortly thereafter, primarily due to stricter Federal Communications Commission (FCC) regulations on radio-frequency interference to nearby electronic devices.[7][8] In April 1983, the Model III was succeeded by the compatible TRS-80 Model 4.
Following the original Model I and its compatible descendants, the TRS-80 name became a generic brand used on other unrelated computer lines sold by Tandy, including the TRS-80 Model II, TRS-80 Model 2000, TRS-80 Model 100, TRS-80 Color Computer, and TRS-80 Pocket Computer.
Software[edit]
BASIC[edit]
Three versions of the BASIC programming language were produced for the Model I. Level I BASIC fits in 4 KB of ROM, and Level II BASIC fits into 12 KB of ROM. Level I is single precision only and had a smaller set of commands. Level II introduced double precision floating point support and has a much wider set of commands. Level II was further enhanced when a disk system was added, allowing for the loading of Disk BASIC.[12]
Level I BASIC is based on Li-Chen Wang's free Tiny BASIC with more functions added by Radio Shack.[15] The accompanying User's Manual for Level 1 by David A. Lien presents lessons on programming with text and cartoons. Lien wrote that it was "written specifically for people who don't know anything about computers ... I want you to have fun with your computer! I don't want you to be afraid of it, because there is nothing to fear".[72][25] Reviewers praised the manual's quality.[12][73][74] Level I BASIC has only two string variables (A$ and B$), 26 numeric variables (A – Z), and one array, A(). Code for functions like SIN(), COS() and TAN() is not included in ROM but printed at the end of the book. The only error messages are "WHAT?" for syntax errors, "HOW?" for arithmetic errors such as division by zero, and "SORRY" for out of memory errors.
Level I BASIC is not tokenized; reserved words are stored literally. In order to maximize the code that fits into 4 KB of memory, users can enter abbreviations for reserved words. For example, writing "P." instead of "PRINT" saves 3 bytes.
Level II BASIC, introduced in mid-1978, was licensed from Microsoft and is required to use the expansion bus and disk drives. Radio Shack always intended for Level I BASIC to be a stopgap until Level II was ready, and the first brochure for the Model I in January 1978 mentioned that Level II BASIC was "coming soon". It is an abridged version of the 16K Extended BASIC, since the Model I has 12 KB of ROM space. According to Bill Gates, "It was a sort of intermediate between 8K BASIC and Extended BASIC. Some features from Extended BASIC such as descriptive errors and user-defined functions were not included, but there were double precision variables and the PRINT USING statement that we wanted to get in. The entire development of Level II BASIC took about four weeks from start to finish." The accompanying manual is more terse and technical than the Level I manual. Original Level I BASIC-equipped machines could be retrofitted to Level II through a ROM replacement performed by Radio Shack for a fee (originally $199). Users with Level I BASIC programs stored on cassette have to convert these to the tokenized Level II BASIC before use. A utility for this was provided with the Level II ROMS.
Disk BASIC allows disk I/O, and in some cases (NewDos/80, MultiDOS, DosPlus, LDOS) adds powerful sorting, searching, full-screen editing, and other features. Level II BASIC reserves some of these keywords and issues a "?L3 ERROR", suggesting a behind-the-scenes change of direction intervened between the creation of the Level II ROMs and the introduction of Disk BASIC.
Microsoft also marketed an enhanced BASIC called Level III BASIC written by Bill Gates,[75] on cassette tape. The cassette contains a "Cassette File" version on one side and a "disk file" version on the second side for disk system users (which was to be saved to disk).[76] Level III BASIC adds most of the functions in the full 16 KB version of BASIC plus many other TRS-80 specific enhancements. Many of Level III BASIC's features are included in the TRS-80 Model III's Level II BASIC and disk BASIC.
Level I BASIC was still offered on the Model I in either 4K or 16K configurations after the introduction of Level II BASIC.
Other programming languages[edit]
Radio Shack published a combined assembler and program editing package called the Series I Assembler Editor.[77] 80 Micro magazine printed a modification enabling it to run under the Model 4's TRSDOS Version 6. Also from Radio Shack was Tiny Pascal.[78]
Microsoft made its Fortran, COBOL and BASCOM BASIC compiler available through Radio Shack.[77]
In 1982, Scientific Time Sharing Corporation published a version of its APL for the TRS-80 Model III as APL*PLUS/80.[79]
Other applications[edit]
Blackjack and backgammon came with the TRS-80, and at its debut, Radio Shack offered four payroll, personal finance, and educational programs on cassette.[12][31]: 3 [13] Its own products' quality was often poor.[80] A critical 1980 80 Micro review of a text adventure described it as "yet another example of Radio Shack's inability to deal with the consumer in a consumer's market". The magazine added, "Sadly, too, as with some other Radio Shack programs, the instructions seem to assume that the reader is either a child or an adult with the mentality of a slightly premature corned beef".[81]
The more than 2,000 Radio Shack franchise stores as of September 1982 sold third-party hardware and software, but the more than 4,300 company-owned stores were at first prohibited from reselling or even mentioning products not sold by Radio Shack itself.[82][83][84][80][85][13] Green stated in 1980 that although "there are more programs for the 80 than for all other systems combined" because of the computer's large market share, "Radio Shack can't advertise this because they are trying as hard as they can to keep this fact a secret from their customers. They don't want the TRS-80 buyers to know that there is anything more than their handful of mediocre programs available", many of which "are disastrous and, I'm sure, doing tremendous damage to the industry".[86][87] Broderbund, founded that year, began by publishing TRS-80 software, but by 1983 cofounder Doug Carlston said that the computer "turned out to be a terrible market because most of the distribution networks were closed, even though there were plenty of machines out there".[88] Green wrote in 1982 that Apple had surpassed Tandy in sales and sales outlets despite the thousands of Radio Shack dealers because it supported third-party development, while "we find the Shack seeming to begrudge any sale not made by them and them alone".[80] Dealers not affiliated with Radio Shack preferred to sell software for other computers and not compete with the company; mail-order sales were also difficult, because company-owned stores did not sell third-party publications like 80 Micro.[83][13]
Charles Tandy reportedly wanted to encourage outside developers but after his death a committee ran the company, which refused to help outside developers, hoping to monopolize the sale of software and peripherals.[13] Leininger reportedly resigned because he disliked the company's bureaucracy after Tandy's death.[42] An author wrote in a 1979 article on the computer's "mystery of machine language graphics control" that "Radio Shack seems to hide the neat little jewels of information a hobbyist needs to make a treasure of the TRS-80". He stated that other than the "excellent" Level I BASIC manual "there has been little information until recently ... TRS-80 owners must be resourceful", reporting that the computer's "keyboard, video, and cassette" functionality were also undocumented.[73] The first book authorized by Tandy with technical information on TRSDOS for the Model I did not appear until after the computer's discontinuation.[85]
By 1982, the company admitted—after no software appeared for the Model 16 after five months—that it should have, like Apple, encouraged third-party developers of products like the killer app VisiCalc.[89][13] (A lengthy 1980 article in a Tandy publication introducing the TRS-80 version of VisiCalc did not mention that the spreadsheet had been available for the Apple II for a year.[90]) However, in the early 1980s, it was not uncommon for small companies and municipalities to write custom programs for computers such as the TRS-80 to process a variety of data. In one case a small town's vehicle fleet was managed from a single TRS-80.[91]
By 1985, the company's Ed Juge stated that other than Scripsit and DeskMate, "we intend to rely mostly on 'big-name', market-proven software from leading software firms".[92] A full suite of office applications became available from the company and others, including the VisiCalc and Multiplan spreadsheets and the Lazy Writer, Electric Pencil, and from Radio Shack itself the Scripsit and SuperScripsit word processors.[93]
Compared to the contemporary Commodore and Apple micros, the TRS-80's block graphics and crude sound were widely considered limited. The faster speed available to the game programmer, not having to processor color data in high resolution, went a long way to compensating for this. TRS-80 arcade games tended to be faster with effects that emphasized motion. This perceived disadvantage did not deter independent software companies such as Big Five Software from producing unlicensed versions of arcade games like Namco's Galaxian, Atari's Asteroids,[94] Taito's Lunar Rescue, Williams's Make Trax,[95] and Exidy's Targ[59] and Venture. Sega's Frogger and Zaxxon were ported to the computer and marketed by Radio Shack.[96][95] Namco/Midway's Pac-Man was cloned by Philip Oliver and distributed by Cornsoft Group as Scarfman.[95][97] Atari's Battlezone was cloned for the Models I/III by Wayne Westmoreland and Terry Gilman and published by Adventure International as Armored Patrol.[98] They also cloned Eliminator (based on Defender) and Donkey Kong;[99] the latter wasn't published until after the TRS-80 was discontinued, because Nintendo refused to license the game.[95]
Some games originally written for other computers were ported to the TRS-80. Microchess has three levels of play and can run in the 4 KB of memory that is standard with the Model I; the classic ELIZA is another TRS-80 port. Both were offered by Radio Shack.[95][100] Apple Panic, itself a clone of Universal's Space Panic, was written for the TRS-80 by Yves Lempereur and published by Funsoft.[101] Epyx's Temple of Apshai runs slowly on the TRS-80.[95] Infocom ported its series of interactive text-based adventure games to the Models I/III; the first, Zork I, was marketed by Radio Shack.[96][95]
Adventure International's text adventures began on the TRS-80,[95] as did Sea Dragon by Westmoreland and Gilman, later ported to the other home micros. Android Nim by Leo Christopherson was rewritten for the Commodore PET and Apple. Many games are unique to the TRS-80, including Duel-N-Droids,[102] also by Christopherson, an early first-person shooter 13 Ghosts by Software Affair (the Orchestra-80, -85 and -90 people)[103][104][105] and shooters like Cosmic Fighter and Defence Command, and strange experimental programs such as Christopherson's Dancing Demon,[95][106] in which the player composes a song for a devil and choreographs his dance steps to the music.[107] Radio Shack offered simple graphics animation programs Micro Movie and Micro Marquee, and Micro Music.[100]
Radio Shack offered a number of programming utilities, including an advanced debugger, a subroutine package, and a cross-reference builder.[108] Probably the most popular utility package was Super Utility written by Kim Watt of Breeze Computing.[109] Other utility software such as Stewart Software's Toolkit offered the first sorted directory, decoding or reset of passwords, and the ability to eliminate parts of TRSDOS that were not needed in order to free up floppy disk space. They also produced the On-Line 80 BBS, a TRSDOS-based Bulletin Board System. Misosys Inc. was a prolific producer of sophisticated TRS-80 utility and language software for all models of TRS-80 from the very beginning.[110]
Perhaps because of the lack of information on TRSDOS[85] and its bugs,[13] by 1982 perhaps more operating systems existed for the TRS-80 than for any other computer.[111] TRSDOS is limited in its capabilities, since like Apple DOS 3.3 on the Apple II, it is mainly conceived of as a way of extending BASIC to support disk drives. Numerous alternative DOSes appeared, the most prominent being LDOS because Radio Shack licensed it from Logical Systems and adopted it as its official DOS for its Models I and III hard disk drive products. Other alternative TRS-80 DOSes included NewDOS from Apparat, Inc., and DoubleDOS, DOSPlus, MicroDOS, UltraDOS (later called Multidos). The DOS for the Model 4 line, TRSDOS Version 6, was produced by and licensed from Logical Systems. It is a derivative of LDOS, enhanced to allow for the new Model 4 hardware such as its all-RAM architecture (no ROM), external 32 KB memory banks, bigger screen and keyboard, and featured new utilities such as a ram disk and a printer spooler.
The memory map of the Model I and III render them incompatible with the standard CP/M OS for Z80 business computers, which loads at hexadecimal address $0000 with TPA (Transient Program Area) starting at $0100; the TRS-80 ROM resides in this address space. Omikron Systems' Mappers board remaps the ROM to run unmodified CP/M programs on the Model I. A customized version of CP/M is available but loses its portability advantage.[112][113] 80 Micro magazine published a do-it-yourself CP/M modification for the Model III.[114]
Manufacturer
July 1980
- $699 (4KB RAM, Level I)
- $999 (16K, Level II)
- $2495 (48K, two 180 KB floppy drives, RS-232C)[116]
September 1983
TRSDOS 1.3, LDOS 5[117]
Zilog Z80A @ 2 MHz
4 KB or 16, 32 or 48 KB
16 rows by 64 or 32 columns, block graphics
optional 512 by 192 pixels, $369 extra[118]
output through cassette port
Model I Z80 code ~ 80% (higher with patches), BASIC 100%
Model I