TheTRS-80 Micro Computer System(TRS-80; later known as theModel Ito distinguish it from successors) is a desktopmicrocomputerlaunched in 1977 and sold byTandy Corporationthrough theirRadio Shackstores. The name is an abbreviation ofTandy/Radio Shack, Z-80 microprocessor.It was one of the earliest mass-produced personal computers.
By 1979, the TRS-80 had the largest selection of software in the microcomputer market.Until 1982, the TRS-80 was the best-selling PC line, outselling theApple II seriesby a factor of 5 according to one analysis.
In mid-1980, the broadly compatibleTRS-80 Model IIIwas released. The Model I was discontinued shortly after, primarily due to stricterFCCregulations on theradio-frequency interferenceit caused in surrounding electronics.In 1983, the Model III was in turn succeeded by the compatibleModel 4.
HistoryRadio Shack Tandy TRS-80 Model I System
In the mid-1970s,Tandy Corporation\'sRadio Shackdivision was a successful American chain of more than 3,000 electronics stores. AfterbuyerDon French purchased aMITS Altairkit computer, he began designing his own and showed it to vice president of manufacturingJohn Roach. Although the design did not impress Roach, the idea of selling a microcomputer did. When the two men visitedNational Semiconductorin California in mid-1976, Steve Leininger\'s expertise on theSC/MPmicroprocessor impressed them. National executives refused to provide Leininger\'s contact information when French and Roach wanted to hire him as a consultant, but they found Leininger working part-time atByte Shopand he and French began working together in June 1976. The company envisioned a kit, but Leininger persuaded the others that because \"too many people can\'t solder\", a preassembled computer would be better.
Tandy had 11 million customers that might buy a microcomputer, but it would be much more expensive than theUS$30median price of a Radio Shack product, and a great risk for the very conservative company.Many opposed the project; one executive told French, \"Don\'t waste my time—we can\'t sell computers.\" As the popularity ofCB radio—at one point more than 20% of Radio Shack\'s sales—declined, however, the company sought new products. In December 1976 French and Leininger received official approval for the project but were told to emphasize cost; for example, leaving out lowercase characters saved US$1.50 in components and reduced the retail price byUS$5. In February 1977 they showed their prototype, running a simple tax-accounting program, toCharles Tandy, head of Tandy Corporation. The program quickly crashed as the computer could not handle theUS$150,000figure that Tandy typed in as his salary, and the two men added support forfloating-point mathto itsTiny BASICto prevent a recurrence. After the demonstration Tandy revealed that he had already leaked the computer\'s existence to the press, so the project was approved.
MITS sold 1,000 Altairs in February 1975, and was selling 10,000 a year. Leininger and French suggested that Radio Shack could sell 50,000 computers,but others disagreed and suggested 1,000 to 3,000 per year at the target US$199 price. Roach persuaded Tandy to agree to build 3,500—the number of Radio Shack stores—so that each store could use a computer for inventory purposes if they did not sell.
Having spent less thanUS$150,000on development, Radio Shack announced the TRS-80 (Tandy Radio Shack) at a New York City press conference on August 3, 1977. It costUS$399, orUS$599with a 12\" monitor and a Radio Shack tape recorder asdata cassettestorage; the most expensive product Radio Shack previously sold was aUS$500stereo. The company hoped that the new computer would help Radio Shack sell higher-priced products, and improve its \"schlocky\" image among customers. Small businesses were the primary target market, followed by educators, then consumers and hobbyists; despite its hobbyist customer base, Radio Shack saw them as \"not the mainstream of the business\".
Although the press conference did not receive much media attention because ofa terrorist bombing elsewhere in the city, the computer received much more publicity at the Personal Computer Faire in Boston two days later. A front-pageAssociated Pressarticle discussed the novelty of a large consumer-electronics company selling a home computer that could \"do a payroll for up to 15 people in a small business, teach children mathematics, store your favorite recipes or keep track of an investment portfolio. It can also play cards.\" Six sacks of mail arrived at Tandy headquarters asking about the computer, over 15,000 people called to purchase a TRS-80—paralyzing the company switchboard—and 250,000 joined the waiting list with a $100 deposit.
Despite the internal skepticism, Radio Shack aggressively entered the market. Company presidentLewis Kornfeldstated when announcing the TRS-80, \"This device is inevitably in the future of everyone in the civilized world—in some way—now and so far as ahead as one can think\", and Tandy\'s 1977annual reportcalled the computer \"probably the most important product we\'ve ever built in a company factory\". Unlike competitorCommodore—which had announced thePETseveral months earlier but had not yet shipped any—Tandy had its own factories and distribution network, and even small towns had Radio Shack stores. The company announced plans to be selling by Christmas a range of peripherals and software for the TRS-80, began shipping computers by September, and opened its first computer-only store in October. Still forecasting 3,000 sales a year, Radio Shack sold over 10,000 TRS-80s Model Is in its first one and a half months of sales, and over 200,000 during the product\'s lifetime;one entered theSmithsonian\'sNational Museum of American History.
The first units, ordered unseen, were delivered in November 1977, and rolled out to the stores the third week of December. The line won popularity with hobbyists, home users, and small-businesses. Tandy Corporation\'s leading positionin whatByteMagazinecalled the \"1977 Trinity\" (Apple,Commodoreand Tandy) had much to do with Tandy\'s retailing the computer through more than 3,000 of its Radio Shack storefronts.Notable features of the original TRS-80 included its full-strokeQWERTYkeyboard, small size, its floating-pointBASICprogramming language, an included monitor, and a starting price of US$600[1](equivalent to US$2300 in 2014). The pre-release price was US$500 and a US$50 deposit was required, with a money-back guarantee at time of delivery.
By 1980InfoWorlddescribed Radio Shack as \"the dominant supplier of small computers\".Kilobaud Microcomputingestimated that it was selling three times as many computers asApple Computer, with both companies ahead of Commodore.By 1981 hundreds of small companies produced TRS-80 software and accessories,andAdam Osbornedescribed Tandy as \"the number-one microcomputer manufacturer\" despite having \"so few roots in microcomputing\".Roach became Tandy\'s CEO that year, Leininger became director of strategic planning, and French founded a software company. Although selling computers did not change the company\'s \"schlocky\" image, the Radio Shack name embarrassed business customers, and Tandy executives disliked the \"Trash-80\" nickname for its products, by 1984 computers accounted for 35% of sales and the company had 500 Tandy Radio Shack Computer Centers.
Following the Model III launch in mid-1980, Tandy initially claimed that the Model I had not been dropped.However, it had been discontinued by the end of the year. Tandy cited one of the main reasons as being the prohibitive cost of redesigning it to meet stricterFCCregulations covering the significant levels ofradio-frequency interferenceemitted by the original design.The Model I radiated so much interference that while playing games anAMradio placed next to the computer could be used to provide sounds.
HardwareRadio Shack Tandy TRS-80 Model I PCBRadio Shack Tandy TRS-80 Model I Rear Panel ConnectorsRadio Shack Tandy TRS-80 Model I Level II ROM Upgrade PCB
The Model I combined themainboardandkeyboardinto one unit, in what was to be a common case design trend throughout the 8-bit microcomputer era, although it had a separate power supply unit. It used aZilog Z80processor clocked at 1.77MHz (later models were shipped with a Z80A). The basic model originally shipped with 4 KB of RAM, and later 16 KB.
PeripheralsCassette tape drive
User data was originally stored oncassette tape. Radio Shack\'s model CTR-41 cassette recorder was included with the US$599 package.The software-basedcassette tape interface was very slow and erratic;Green described it as \"crummy ... drives users up the wall\", and the first issue of80 Microhad three articles on how to improve cassette performance.It was sensitive to audio volume changes,and the machine gave only the very crudest indication as to whether the correct volume was set, via a blinking character on screen when data was being loaded. To find the correct volume, one would sometimes have to attempt to load a program once, adjusting volume until the machine picked up the data, then reset the machine, rewind the tape and attempt the load again. Users quickly learned to save a file three or more times in hopes that one copy would prove to be readable. Automatic gain control or indicator circuits could be constructed to compensate for this (the owner\'s manual provided complete circuit diagrams for the whole machine, including the peripheral interfaces, with notes on operation).
An alternative tape interface could receive transmissions from theBBC\'sChip Shopprogramme in the UK, which broadcast software for several different microcomputers over the radio. A special program (loaded using the conventional tape interface) was needed to access the custom interface. Tandy eventually replaced the CTR-41 unit with the CTR-80 which had built-in AGC circuitry (and no volume control). This helped the situation, but tape operation was still unreliable.
TRS-80s with Level I BASIC read and wrote tapes at 250 bits per second (31.25 bytes per second); Level II BASIC doubled this to 500 bits per second (62.5 bytes per second). Some programmers wrote machine language programs that would increase the speed to up to 1800 bits per second without loss in reliability.
For loading and storing data, no hardware controller existed. Instead, the processor created the sound itself by switching the output voltage between three states, creating very crude sine wave audio.
The first models of the Model I also had problems reading from the cassette drives. Tandy eventually offered a small board which was installed in a service center to correct earlier models. The ROMs in later models were modified to correct this.
Hard drive
Radio Shack introduced a 5 MB hard-drive unit for the TRS-80 Models I and III (and later Model 4) in 1983. The size of the unit was about the same as a modern desktop computer enclosure. The initial retail price (US$2495) is equivalent to US$5900 in 2014.
SoftwareBASIC
Three versions of theBASICprogramming language were produced for the Model I.Level I BASICfit in 4 KB ofROM, andLevel II BASICfit into 12 KB of ROM. Level I was single precision only and had a smaller set of commands. Level II introduced double precision floating point support and had a much wider set of commands. Level II was further enhanced when a disk system was added, allowing for the loading ofDisk BASIC.
Level I Basic was based onLi-Chen Wang\'s freeTiny BASIC, additional functions added by Radio Shack.It had an excellent manualwritten byDavid Lien, which presented lessons on programming with text and humorous graphics, making the subjects very easy to understand. Lien wrote that it was \"written specifically for people who don\'t know anything about computers ... I want you to have fun with your computer! I don\'t want you to be afraid of it, because there is nothing to fear ...\"Level I BASIC had only twostringvariables (A$andB$), 26 numeric variables (A-Z) and one array,A(). Code for functions like SIN(), COS() and TAN() was not included in ROM but printed at the end of the book. The only error messages were: \"WHAT?\" for syntax errors, \"HOW?\" for arithmetic errors such asdivision by zero, and \"SORRY\" forout of memoryerrors.
Level I BASIC was nottokenized—reserved words were stored literally. In order to maximize the code that could be crammed into 4K of memory users could enter abbreviations for reserved words. For example, writing \"P.\" instead of \"PRINT\" thus saving 3 bytes.
Level II BASIC was licensed fromMicrosoft. It was a cut-down version of the 16 KBExtended BASIC, since the Model I had 12 KB of ROM space. The accompanying manual was not nearly as colorful and suited for beginning programmers as the Level I BASIC 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 US$199). Users with Level I BASIC programs stored on cassette had to convert these to the non-tokenized Level II BASIC before use. A utility for this was provided with the Level II ROMS.
Disk BASIC added the ability to perform disk I/O, and in some cases (NewDos/80, MultiDOS, DosPlus, LDOS) added powerful sorting, searching, full screen editing, and other features. Level II BASIC reserved some of these keywords and issued 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 a tape-cassette based enhanced BASIC calledLevel III BASIC. This added most of the functions in the full 16 KB version of BASIC.
Reception
Dan Fylstra, among the first owners, wrote inBYTEin April 1978 that as an \"\'appliance\' computer ... the TRS-80 brings the personal computer a good deal closer to the average customer\", suitable for home and light business use. He concluded that it \"is not the only alternative for the aspiring personal computer user, but it is a strong contender.\"Jerry Pournellewrote in 1980 that \"the basic TRS-80 is a lot of computer for the money. It comes ready to run right out of the box, and it can be set up by three boys– ages 9, 11, and 13 ... The Tandy/Radio Shack documentation is excellent, and there are a lot of good programs available\". He noted that while \"just about every component of my TRS-80 has taken a trip to the local store to be fixed\", \"none of that cost me anything; it wasn\'t even inconvenient, especially with local Radio Shacks all over the place ... Given the price of the TRS-80, Tandy\'s quality control is better than you\'d expect.\" Pournelle criticized the quality of Tandy\'s application and system software—including the \"needlessly complex\" TRSDOS—and high cost of its peripherals. He reported, however, that with the Omikron board, additional memory, and 8- and 5 1/4-inch disk drives, \"for a total cost of under $5000, you have a 48 K-byte machine capable of running all the TRS-80 programs, CP/M software, and top-grade text editors likeWord Master,Magic Wand, Electric Pencil, and the Proteus editor ... all without building a single kit\".
Compatible successors
Tandy would go on to replace the Model I with the broadly compatible Model III in 1980. (TheTRS-80 Model IIhad been an entirely different and incompatible design). The Model III was in turn succeeded by the backward-compatible Model 4 in 1983.
Model III
TRS-80 Model III
In July 1980 Tandy released theTRS-80 Model III. The improvements of the Model III over the Model I included built-in lower case, a better keyboard, elimination of the cable spaghetti, 1500-baud cassette interface, and a faster (2.03MHz) Z-80 processor. Shortly after, Model I production was discontinued as it did not comply with newFCCregulations as of January 1, 1981 regardingelectromagnetic interference.
The Model III could run about 80% of Model I software, but used an incompatible disk format.Customers and developers complained of bugs in its BASIC and the TRSDOS operating system.The computer also came with the option of integrated disk drives.
InfoWorldapproved of the Model III\'s single-unit design, simplified cable management, and improvements such as lack of keyboard bounce and improved disk reliability. The reviewer, a former Model I owner, stated \"I\'m impressed\" and that \"had the Model III been available, it\'s probable that I wouldn\'t have sold it\". He concluded, \"If you\'re looking for a computer that\'s not too expensive but that performs well, you would be wise to test the Model III—you might end up buying it.\"
