TRS-80 Model I
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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 Tandy Corporation was an American family-owned leather goods company based in Fort Worth, Texas, United States. Tandy Leather was founded in 1919 as a leather supply store. By the end of the 1950s, under the tutelage of then-CEO Charles Tandy, ...
through their
Radio Shack RadioShack, formerly RadioShack Corporation, is an American retailer founded in 1921. At its peak in 1999, RadioShack operated over 8,000 worldwide stores named RadioShack or Tandy Electronics in the United States, Mexico, United Kingdom, Austra ...
stores. The name is an abbreviation of ''Tandy Radio Shack, Z80 icroprocessor'. It is one of the earliest mass-produced and mass-marketed retail home computers. The TRS-80 has a full-stroke
QWERTY QWERTY () is a keyboard layout for Latin-script alphabets. The name comes from the order of the first six Computer keyboard keys#Types, keys on the top left letter row of the keyboard ( ). The QWERTY design is based on a layout created f ...
keyboard, the
Zilog Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples wer ...
processor, 4 KB
dynamic random-access memory Dynamic random-access memory (dynamic RAM or DRAM) is a type of random-access semiconductor memory that stores each bit of data in a memory cell, usually consisting of a tiny capacitor and a transistor, both typically based on metal-oxide ...
(DRAM) standard memory, small size and desk area, floating-point
Level I BASIC Level I BASIC is a dialect of the BASIC programming language that shipped with the first TRS-80, the TRS-80 Model I. Background Tandy-employee Steve Leininger had written the first draft of the NIBL (National Industrial Basic Language) BASIC in ...
language interpreter in
read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...
(ROM), 64-character per line
video monitor A display device is an output device for presentation of information in visual or tactile form (the latter used for example in tactile electronic displays for blind people). When the input information that is supplied has an electrical signal the ...
, and a starting price of US$600 (equivalent to US$ in ). 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 to serious use. It lacked support for lowercase characters, which also 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 A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...
drives and/or
hard disk drive A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...
s. 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. Until 1982, the TRS-80 was the best-selling PC line, outselling the Apple II series by a factor of five according to one analysis. In mid-1980, the broadly compatible TRS-80 Model III was released. The Model I was discontinued shortly thereafter, primarily due to stricter
Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdiction ...
(FCC) regulations on
radio-frequency interference Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electros ...
to nearby electronic devices. In April 1983, the Model III was succeeded by the compatible
TRS-80 Model 4 The TRS-80 Model 4 is the last Z80-based home computer family by Radio Shack RadioShack, formerly RadioShack Corporation, is an American retailer founded in 1921. At its peak in 1999, RadioShack operated over 8,000 worldwide stores named Rad ...
. 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 The TRS-80 Model II is a computer system launched by Tandy in October 1979, and targeted at the small-business market. It is not an upgrade of the original TRS-80 Model I, but a new system. The Model II was succeeded by the compatible TRS-80 Mode ...
, TRS-80 Model 2000,
TRS-80 Model 100 The TRS-80 Model 100 is a portable computer introduced in April 26th, 1983. It is one of the first notebook-style computers, featuring a keyboard and liquid crystal display, in a battery-powered package roughly the size and shape of a notepad or ...
,
TRS-80 Color Computer The RadioShack TRS-80 Color Computer, later marketed as the Tandy Color Computer and sometimes nicknamed the CoCo, is a line of home computers developed and sold by Tandy Corporation. Despite sharing a name with the earlier TRS-80, the Color Com ...
, and
TRS-80 Pocket Computer The Tandy Pocket Computer or TRS-80 Pocket Computer is one of a line of 1980s small pocket computers—calculator-sized programmable computing devices—sold by Tandy Corporation under the "''Tandy''" or "''Radio Shack TRS-80''" brands. A ...
.


History


Development

In the mid-1970s,
Tandy Corporation Tandy Corporation was an American family-owned leather goods company based in Fort Worth, Texas, United States. Tandy Leather was founded in 1919 as a leather supply store. By the end of the 1950s, under the tutelage of then-CEO Charles Tandy, ...
's
Radio Shack RadioShack, formerly RadioShack Corporation, is an American retailer founded in 1921. At its peak in 1999, RadioShack operated over 8,000 worldwide stores named RadioShack or Tandy Electronics in the United States, Mexico, United Kingdom, Austra ...
division was a successful American chain of more than 3,000 electronics stores. Among the Tandy employees who purchased a
MITS Altair The Altair 8800 is a microcomputer designed in 1974 by MITS and based on the Intel 8080 CPU. Interest grew quickly after it was featured on the cover of the January 1975 issue of Popular Electronics and was sold by mail order through advertisemen ...
kit computer An electronic kit is a package of electrical components used to build an electronic device. Generally, kits are composed of electronic components, a circuit diagram (schematic), assembly instructions and often a printed circuit board (PCB) or ...
was
buyer Procurement is the method of discovering and agreeing to terms and purchasing goods, services, or other works from an external source, often with the use of a tendering or competitive bidding process. When a government agency buys goods or serv ...
Don French, who began designing his own computer and showed it to vice president of manufacturing John V. Roach, Tandy's former electronic data processing manager. Although the design did not impress Roach, the idea of selling a microcomputer did. When the two men visited
National Semiconductor National Semiconductor was an American semiconductor manufacturer which specialized in analog devices and subsystems, formerly with headquarters in Santa Clara, California. The company produced power management integrated circuits, display dr ...
in California in mid-1976,
Homebrew Computer Club The Homebrew Computer Club was an early computer hobbyist group in Menlo Park, California, which met from March 1975 to December 1986. The club had an influential role in the development of the microcomputer revolution and the rise of that asp ...
member Steve Leininger's expertise on the
SC/MP National Semiconductor's INS8060, or SC/MP (pronounced ''scamp'') for Simple Cost-effective Micro Processor, is an early 8-bit microprocessor which became available in April 1976. A unique feature of the SC/MP is a daisy-chained control pin that a ...
microprocessor 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 at
Byte Shop The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
. Leininger was unhappy at National, his wife wanted a better job, and Texas did not have a
state income tax In addition to Federal government of the United States, federal Income tax in the United States, income tax collected by the United States, most individual U.S. states collect a state income tax. Some local governments also impose an income tax, ...
. Hired for his technical and retail experience, Leininger began working with French 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 the median price of a Radio Shack product, and a great risk for the very conservative company. Executives feared losing money as
Sears Sears, Roebuck and Co. ( ), commonly known as Sears, is an American chain of department stores founded in 1892 by Richard Warren Sears and Alvah Curtis Roebuck and reincorporated in 1906 by Richard Sears and Julius Rosenwald, with what began a ...
did with
Cartrivision Cartrivision is an analog videocassette format introduced in 1972, and the first format to offer feature films for consumer rental. and many opposed the project; one executive told French, "Don't waste my time—we can't sell computers." As the popularity of
CB radio Citizens band radio (also known as CB radio), used in many countries, is a land mobile radio system, a system allowing short-distance person-to-many persons bidirectional voice communication among individuals, using two way radios operating on ...
—at one point comprising 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 savings; for example, leaving out lowercase characters saved US$1.50 in components and reduced the retail price by . The original retail price required
manufacturing cost Manufacturing cost is the sum of costs of all resources consumed in the process of making a product. The manufacturing cost is classified into three categories: direct materials cost, direct labor cost and manufacturing overhead. It is a factor in ...
of ; the first design had a
membrane keyboard A membrane keyboard is a computer keyboard whose "keys" are not separate, moving parts, as with the majority of other keyboards, but rather are pressure pads that have only outlines and symbols printed on a flat, flexible surface. Very little, ...
and no video monitor. Leininger persuaded Roach and French to include a better keyboard; it, a monitor,
datacassette Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9-t ...
storage, and other features required a higher retail price to provide Tandy's typical profit margin. In February 1977 they showed their prototype, running a simple tax-accounting program, to Charles Tandy, head of Tandy Corporation. The program quickly crashed as the computer's implementation of
Tiny BASIC Tiny BASIC is a family of Programming language#Dialects, flavors and implementations, dialects of the BASIC programming language that can fit into 4 or fewer kilobyte, KBs of random-access memory, memory. Tiny BASIC was designed in response to th ...
could not handle the figure that Tandy typed in as his salary, and the two men added support for floating-point math to its
Level I BASIC Level I BASIC is a dialect of the BASIC programming language that shipped with the first TRS-80, the TRS-80 Model I. Background Tandy-employee Steve Leininger had written the first draft of the NIBL (National Industrial Basic Language) BASIC in ...
to prevent a recurrence. The project was formally approved on 2 February 1977; Tandy revealed that he had already leaked the computer's existence to the press. When first inspecting the prototype, he remarked that even if it did not sell, the project could be worthy if only for the publicity it might generate. MITS sold 1,000 Altairs in February 1975, and was selling 10,000 a year. When Charles Tandy asked who would buy the computer, company president Lewis Kornfeld admitted that they did not know if anyone would, but suggested that small businesses and schools might. Knowing that demand was very strong for the Altair—which cost more than $1,000 with a monitor—Leininger suggested that Radio Shack could sell 50,000 computers, but no one else believed him; Roach called the figure "horseshit", as the company had never sold that many of anything at that price. Roach and Kornfeld suggested 1,000 to 3,000 per year; 3,000 was the quantity the company would have to produce to buy the components in bulk. 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.
RCA The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...
agreed to supply the video monitor—a black-and-white television with the tuner and speakers removed—after others refused because of Tandy's low initial volume of production. Tandy used the black-and-silver colors of the RCA CRT unit's cabinet for the TRS-80 units also.


Announcement

Having spent less than on development, Radio Shack announced the TRS-80 (Tandy Radio Shack) at a New York City press conference on August 3, 1977. It cost ($ today), or ($ today) with a 12" monitor and a Radio Shack tape recorder; the most expensive product Radio Shack previously sold was a stereo. 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" and "never our large market". Although the press conference did not receive much media attention because of a terrorist bombing elsewhere in the city, the computer received much more publicity at
Boston University Boston University (BU) is a private research university in Boston, Massachusetts. The university is nonsectarian, but has a historical affiliation with the United Methodist Church. It was founded in 1839 by Methodists with its original campu ...
's Personal Computer Fair two days later. A front-page
Associated Press The Associated Press (AP) is an American non-profit news agency headquartered in New York City. Founded in 1846, it operates as a cooperative, unincorporated association. It produces news reports that are distributed to its members, U.S. newspa ...
article 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. The company advertised "''The $599 personal computer''" as "the most important, useful, exciting, electronic product of our time". Kornfeld stated 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 1977
annual report An annual report is a comprehensive report on a company's activities throughout the preceding year. Annual reports are intended to give shareholders and other interested people information about the company's activities and financial performance. ...
called the computer "probably the most important product we've ever built in a company factory". Unlike competitor
Commodore Commodore may refer to: Ranks * Commodore (rank), a naval rank ** Commodore (Royal Navy), in the United Kingdom ** Commodore (United States) ** Commodore (Canada) ** Commodore (Finland) ** Commodore (Germany) or ''Kommodore'' * Air commodore ...
—which had announced the
PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence ...
several months earlier but had not yet shipped any—Tandy had its own factories (capable of producing 18,000 computers a month) 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, opened its first computer-only store in October, and delivered 5,000 computers to customers by December. Still forecasting 3,000 sales a year, Radio Shack sold over 10,000 TRS-80s in its first one and a half months of sales, 55,000 in its first year, and over 200,000 during the product's lifetime; one entered the Smithsonian's
National Museum of American History The National Museum of American History: Kenneth E. Behring Center collects, preserves, and displays the heritage of the United States in the areas of social, political, cultural, scientific, and military history. Among the items on display is t ...
. By mid-1978 the waits of two months or more for delivery were over, and the company could state in advertisements that TRS-80 was "on demonstration and available ''from stock now'' at every Radio Shack store in this community!"


Delivery

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 position in what ''Byte'' magazine called the "1977 Trinity" (
Apple Computer Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...
,
Commodore Commodore may refer to: Ranks * Commodore (rank), a naval rank ** Commodore (Royal Navy), in the United Kingdom ** Commodore (United States) ** Commodore (Canada) ** Commodore (Finland) ** Commodore (Germany) or ''Kommodore'' * Air commodore ...
, and Tandy) had much to do with Tandy's retailing the computer through more than 3,000 of its Radio Shack storefronts in the USA. Tandy claimed it had "7000
adio Shack Adio may refer to: Business *Adio (company), the former skateboard footwear and apparel company Music Songs *Adio (song), "Adio" (song), a song by Montenegrin recording artist Knez that represented Montenegro at the Eurovision Song Contest 2015 * ...
stores in 40 countries". The pre-release price for the basic system (CPU/keyboard and video monitor) was and a deposit was required, with a money-back guarantee at time of delivery. By 1978, Tandy/Radio Shack promoted itself as "The Biggest Name in Little Computers". By 1979 1,600 employees built computers in six factories. ''
Kilobaud Microcomputing ''Kilobaud Microcomputing'' was a magazine dedicated to the computer homebrew hobbyists from 1977 to 1983. How ''kilobaud'' started Wayne Green, the editor and publisher of ''kilobaud'', had been the publisher of ''BYTE'' magazine, (another i ...
'' estimated in 1980 that Tandy was selling three times as many computers as
Apple Computer Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...
, with both companies ahead of Commodore. By 1981, ''
InfoWorld ''InfoWorld'' (abbreviated IW) is an information technology media business. Founded in 1978, it began as a monthly magazine. In 2007, it transitioned to a web-only publication. Its parent company today is International Data Group, and its siste ...
'' described Radio Shack as "the dominant supplier of small computers". Hundreds of small companies produced TRS-80 software and accessories, and
Adam Osborne Adam Osborne (March 6, 1939 – March 18, 2003) was a British author, book and software publisher, and computer designer who founded several companies in the United States and elsewhere. He introduced the Osborne 1, the first commercially su ...
described Tandy as "the number-one microcomputer manufacturer" despite having "so few roots in microcomputing". That year Leininger left his job as director for advanced research; French had left to found a software company, while Roach became Tandy's CEO. 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, however, and the company had 500 Tandy Radio Shack Computer Centers.


Model II and III

By 1979, when Radio Shack launched the business-oriented, and incompatible,
TRS-80 Model II The TRS-80 Model II is a computer system launched by Tandy in October 1979, and targeted at the small-business market. It is not an upgrade of the original TRS-80 Model I, but a new system. The Model II was succeeded by the compatible TRS-80 Mode ...
, the TRS-80 was officially renamed the TRS-80 Model I to distinguish the two product lines. After some exhibitors at the 1979 Northeast Computer Show were forced to clarify that their products bearing the TRS-80 name were not affiliated with Radio Shack, publications and advertisers briefly began to use "S-80" generically rather than "TRS-80" under scare of legal action, though this never materialized. Following the Model III launch in mid-1980, Tandy stated that the Model I was still sold, but it was discontinued by the end of the year. Tandy cited one of the main reasons as being the prohibitive cost of redesigning it to meet stricter
FCC The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
regulations covering the significant levels of
radio-frequency interference Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electros ...
emitted by the original design. The Model I radiated so much interference that, while playing games, an AM radio placed next to the computer could be used to provide sounds. Radio Shack offered upgrades (double-density floppy controller, LDOS, memory, reliable keyboard with numeric keypad, lowercase, Level II, RS-232C) as late as 1985.


Hardware

The Model I combines the
mainboard A motherboard (also called mainboard, main circuit board, mb, mboard, backplane board, base board, system board, logic board (only in Apple computers) or mobo) is the main printed circuit board (PCB) in general-purpose computers and other expan ...
and
keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Musi ...
into one unit, which became a design trend in the 8-bit microcomputer era, although the Model I has a separate power supply unit. It uses a
Zilog Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples wer ...
processor clocked at 1.78 MHz (later models shipped with a Z80A). The initial Level I machines shipped in late 1977-early 1978 have only 4 KB of RAM. After the Expansion Interface and Level II BASIC were introduced in mid-1978, RAM configurations of 16 KB and up were offered (the first 16 KB was in the Model I itself and the remaining RAM in the Expansion Interface). The OS ROMs, I/O area, video memory and OS work space occupy the first 16 KB of memory space on the Model I. The remaining 48 KB of the 64 KB
memory map In computer science, a memory map is a structure of data (which usually resides in memory itself) that indicates how memory is laid out. The term "memory map" can have different meanings in different contexts. *It is the fastest and most flexible ...
space is available for program use, subject to the amount of physical RAM installed. Although the Z80 CPU can use port-based I/O, the Model I's I/O is memory-mapped aside from the
cassette tape The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Ottens ...
and
RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such ...
serial ports.


Keyboard

The TRS-80 Model I keyboard uses mechanical switches that suffer from " keyboard bounce", resulting in multiple letters being typed per keystroke. The problem was described in
Wayne Green Wayne Sanger Green II (September 3, 1922 – September 13, 2013) was an American publisher, writer, and consultant. Green was editor of '' CQ'' magazine before he went on to found '' 73'', ''80 Micro'', ''Byte'', '' CD Review'', ''Cold Fusion'', ...
's editorial in the first issue of ''
80 Micro ''80 Micro'' was a computer magazine, published between 1980 and 1988, that featured program listings, products and reviews for the TRS-80. History Wayne Green, the creator of many magazines such as '' 73'', founded ''80 Microcomputing'' as a ...
''. Dirt, cigarette smoke, or other contamination enters the unsealed key switches, causing
electrical noise In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics, and central to the ...
that the computer detects as multiple presses. The key switches can be cleaned, but the bounce recurs when the keyboard is reexposed to the contaminating environment. Keyboard bounce only occurs in Model I computers with Level II BASIC
firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...
; Level I BASIC has a "debounce" delay to the keyboard driver to avoid the noisy switch contacts. Tandy's utility, the Model III, the last Model I firmware, and most third-party operating systems also implement the software fix, and Tandy changed the keyboard during the Model III's lifetime to an
Alps Electric is a Japanese multinational corporation, headquartered in Tokyo, Japan, producing electronic devices, including switches, potentiometers, sensors, encoders and touchpads. The company was established in 1948 as Kataoka Electric Co., Ltd. and ch ...
design with sealed switches. The Alps keyboard was available as an upgrade for the Model I for $79. The keyboard is
memory mapped In computer science, a memory map is a structure of data (which usually resides in memory itself) that indicates how memory is laid out. The term "memory map" can have different meanings in different contexts. *It is the fastest and most flexible ...
so that certain locations in the processor's memory space correspond to the status of a group of keys.


Video and audio

The color of the 12" KCS 172 RCA monitor's text is faintly blue (the standard P4 phosphor used in black-and white televisions). Green and amber filters, or replacement tubes to reduce eye fatigue were popular aftermarket items. Later models came with a green-on-black display. Complaints about the video display quality were common. As Green wrote, "hells bells,
he monitor He or HE may refer to: Language * He (pronoun), an English pronoun * He (kana), the romanization of the Japanese kana へ * He (letter), the fifth letter of many Semitic alphabets * He (Cyrillic), a letter of the Cyrillic script called ''He'' ...
''is'' a cheap black and white television set with a bit of conversion for computer use". (The computer could be purchased without the Radio Shack monitor.) CPU access to the screen memory causes visible flicker. The bus arbitration logic blocks video display refresh (video RAM reads) during CPU writes to the VRAM, causing a short black line. This has little effect on normal BASIC programs, but fast programs made with
assembly language In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...
can be affected. Software authors worked to minimize the effect, and many arcade-style games are available for the Tandy TRS-80. Because of bandwidth problems in the interface card that replaced the TV's tuner, the display loses horizontal sync if large areas of white are displayed. A simple half-hour hardware fix corrects the problem. The graphics are displayed at a resolution of 64×16 character positions on a screen measuring wide and tall. Each character is composed of a 2×3 matrix of pixels, and corresponds to one byte of the 1 KB video memory used by the TRS-80. In each of those bytes, the first six bits control which pixel is displayed. The seventh bit is ignored, and the eighth toggles graphics mode. The reason that the seventh bit is ignored is due to the company's decision to have only seven 2102 static RAM chips installed on the computer's motherboard instead of eight to keep the manufacturing cost low. Thus, there are no lowercase letters in the
TRS-80 character set The TRS-80 computer manufacturered by Tandy / Radio Shack contains an 8-bit character set. It is partially derived from ASCII, and shares the code points from 32 - 95 on the standard model. Code points 96 - 127 are supported on models that have bee ...
of an unmodified Model I, and the number of both graphics symbols and alphanumeric symbols is 64. This can be worked around by deleting the unused bit and piggybacking an eighth 2102 chip onto another. The alphanumeric symbols are displayed in 5×7 matrices of
pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the smal ...
s. The 1978 manual for the popular word processor
Electric Pencil Electric Pencil, released in December 1976 by Michael Shrayer, was the first word processor for home computers. History In 1975, Michael Shrayer had moved to California after 20 years as a New York filmmaker. Enjoying assembling electronic kits, ...
came with instructions for modifying the computer. Although the modification needs to be disabled for Level II BASIC, its design became the industry standard and was widely sold in kit form, along with an eighth 2102 chip. Later models came with the hardware for the lowercase character set to be displayed with descenders. With higher-density RAM chips and purpose-built monitors, higher resolution crisp displays are obtainable; 80x24 character displays are available in the Model II, Model 4, and later systems. The Model I has no built-in speaker. Square wave tones can be produced by outputting data to the cassette port and plugging an amplifier into the cassette "Mic" line. Most games use this ability for sound effects. An adapter was available to use Atari joysticks.


Peripherals


Cassette tape drive

User data was originally stored on
cassette tape The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Ottens ...
. Radio Shack's model CTR-41 cassette recorder was included with the US$599 package. The software-based cassette tape interface is slow and erratic; Green described it as "crummy ... drives users up the wall", and the first issue of ''80 Micro'' has three articles on how to improve cassette performance. It is sensitive to audio volume, and the computer gives only a crude indication as to whether the correct volume was set, via a blinking character on screen while data is loaded. To find the correct volume at first use, the load is started and the volume is adjusted until the TRS-80 picked up the data. Then it is halted to rewind the tape and restart the load. Users were instructed to save multiple copies of a software program file, especially if audio tape cassettes instead of certified data tape was used. Automatic gain control or indicator circuits can be constructed to improve the loading process (the owner's manual provides complete circuit diagrams for the whole machine, including the peripheral interfaces, with notes on operation). An alternative to using tape was data transmissions from the
BBC #REDIRECT BBC #REDIRECT BBC Here i going to introduce about the best teacher of my life b BALAJI sir. He is the precious gift that I got befor 2yrs . How has helped and thought all the concept and made my success in the 10th board exam. ...
...
's ''Chip Shop'' programme in the UK, which broadcast software for several different microcomputers over the radio. A special program was loaded using the conventional tape interface. Then the radio broadcast was connected to the cassette tape 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 is still unreliable. TRS-80 Model I computers with Level I BASIC read and wrote tapes at 250 baud (about 30 bytes per second); Level II BASIC doubles this to 500 baud (about 60 bytes per second). Some programmers wrote machine-language programs that increases the speed to up to 2,000 bits per second without a loss of reliability on their tape recorders. With the Model III and improved electronics in the cassette interface, the standard speed increased to 1,500 baud that works quite reliably on most tape recorders. For loading and storing data from tape, the CPU creates the sound by switching the output voltage between three states, creating crude sine wave audio. The first version of the Model I also has a hardware problem that complicated loading programs from cassette recorders. Tandy offered a small board which was installed at a service center to correct the issue. The ROMs in later models were modified to correct this.


Model I Expansion Interface

Only the Model I uses an Expansion Interface; all later models have everything integrated in the same housing. The TRS-80 does not use the
S-100 bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus designed in 1974 as a part of the Altair 8800. The bus was the first industry standard expansion bus for the microcomputer industry. computers, consisting of p ...
like other early 8080 and Z80-based computers. A proprietary Expansion Interface (E/I) box, which fits under the video monitor and served as its base, was offered instead. Standard features of the E/I are a floppy disk controller, Centronics
parallel port In computing, a parallel port is a type of interface found on early computers (personal and otherwise) for connecting peripherals. The name refers to the way the data is sent; parallel ports send multiple bits of data at once ( parallel ...
for a printer, and added cassette connector. Optionally, an extra 16 or 32 KB of RAM can be installed and a daughterboard with an RS-232 port. The 40-conductor expansion connector passes through to a card edge connector, which permits the addition of external peripherals such as an outboard hard disk drive, a
voice synthesizer Speech synthesis is the artificial production of human speech. A computer system used for this purpose is called a speech synthesizer, and can be implemented in software or Computer hardware, hardware products. A text-to-speech (TTS) system conve ...
, or a VOXBOX voice recognition unit. Originally, printing with the Model I requires the Expansion Interface, but later Tandy made an alternative parallel printer interface available. The Model I Expansion Interface is the most troublesome part of the TRS-80 Model I system. It went through several revisions. The E/I connects to the CPU/keyboard with a 6-inch ribbon cable which is unshielded against RF interference and its card edge connector tends to oxidize due to its
base metal A base metal is a common and inexpensive metal, as opposed to a precious metal such as gold or silver. In numismatics, coins often derived their value from the precious metal content; however, base metals have also been used in coins in the past ...
contacts. This demands periodic cleaning with a pencil eraser in order to avoid spontaneous reboots, which contributes to its "Trash-80" sobriquet. Aftermarket connectors plated with gold solves this problem permanently. Software developers also responded by devising a recovery method which became a standard feature of many commercial programs. They accept an "asterisk parameter", an asterisk (star) character typed following the program name when the program is run from the TRSDOS Ready prompt. When used following a spontaneous reboot (or an accidental reset, program crash, or exit to TRSDOS without saving data to disk), the program loads without initializing its data area(s), preserving any program data still present from the pre-reboot session. Thus, for example, if a
VisiCalc VisiCalc (for "visible calculator") is the first spreadsheet computer program for personal computers, originally released for Apple II by VisiCorp on 17 October 1979. It is often considered the application that turned the microcomputer from a hob ...
user suffers a spontaneous reboot, to recover data the user enters at TRSDOS Ready, and Visicalc restores the previous computing session intact.The user must take care not to do anything that could cause memory to be overwritten; they should recover immediately without running any other programs. Since programs may start automatically via the TRSDOS AUTO command, during a spontaneous reboot they take the precaution of holding down to prevent this from happening. It takes TRSDOS some half dozen seconds to load from floppy disk; the user has this long to keep an AUTO'd program from loading. This star parameter became a standard for many software applications running on the Models III and 4; for instance LS-DOS's TED and Prosoft's Allwrite. The power button on the E/I is difficult to operate as it is recessed so as to guard against the user accidentally hitting it and turning it off while in use. A pencil eraser or similar object is used to depress the power button and the E/I has no power LED, making it difficult to determine if it is running or not. The expansion unit requires a second power supply, identical to the base unit power supply. An interior recess holds both supplies. The user is instructed to power on and power off all peripherals in proper order to avoid corrupting data or potentially damaging hardware components. The manuals for the TRS-80 advise turning on the monitor first, then any peripherals attached to the E/I (if multiple disk drives are attached, the last drive on the chain is to be powered on first and work down from there), the E/I, and the computer last. When powering down, the computer is to be turned off first, followed by the monitor, E/I, and peripherals. In addition, users are instructed to remove all disks from the drives during power up or down (or else leave the drive door open to disengage the read/write head from the disk). This is because a transient electrical surge from the drive's read/write head would create a magnetic pulse that could corrupt data. This was a common problem on many early floppy drives. The E/I displays a screen full of garbage characters on power up and unless a bootable system disk is present in Drive 0, it hangs there until the user either presses on the back of the computer, which causes it to attempt to boot the disk again, or was pressed, which drops the computer into BASIC. Due to the above-mentioned problems with potentially corrupting disks, it is recommended to power up to the garbage screen with the disk drives empty, insert a system disk, and then hit . ''InfoWorld'' compared the cable spaghetti connecting the TRS-80 Model I's various components to the snakes in ''
Raiders of the Lost Ark ''Raiders of the Lost Ark'' is a 1981 American action-adventure film directed by Steven Spielberg and written by Lawrence Kasdan, based on a story by George Lucas and Philip Kaufman. It stars Harrison Ford, Karen Allen, Paul Freeman, Ronal ...
''. Radio Shack offered a "TRS-80 System Desk" that concealed nearly all the cabling. It can accommodate the complete computer system plus up to four floppy drives and the Quick Printer. Since the cable connecting the Expansion Interface carries the system bus, it is short (about 6 inches). The user has no choice but to place the E/I directly behind the computer with the monitor on top. This causes problems for a non-Tandy monitor whose case did not fit the mounting holes. Also, the friction fit of the edge connector on the already short interconnect cable makes it possible to disconnect the system bus from the CPU if either unit is bumped during operation.


Floppy disk drives

Radio Shack introduced floppy drives in July 1978, about six months after the Model I went on sale. The Model I disk operating system
TRSDOS TRSDOS (which stands for the Tandy Radio Shack Disk Operating System) is the operating system for the Tandy TRS-80 line of eight-bit Zilog Z80 microcomputers that were sold through Radio Shack from 1977 through 1991. Tandy's manuals recommended th ...
was written by Randy Cook under license from Radio Shack; Randy claimed to have been paid $3000 for it. The first version released to the public was a buggy v2.0. This was quickly replaced by v2.1. Floppy disk operation requires buying the Expansion Interface, which included a single-density floppy disk interface (with a formatted capacity of 85K) based on the Western Digital 1771 single-density floppy disk controller chip. The industry standard
Shugart Associates Shugart Associates (later Shugart Corporation) was a computer peripheral manufacturer that dominated the floppy disk drive market in the late 1970s and is famous for introducing the -inch "Minifloppy" floppy disk drive. In 1979 it was one of the f ...
SA-400 minifloppy disk drive was used. Four floppy drives can be daisy-chained to the Model I. The last drive in the chain is supposed to have a termination resistor installed but often it is not needed as it is integrated into later cables. Demand for Model I drives greatly exceeded supply at first. The drive is unreliable, partly since the interface lacked an external data separator (buffer). The early version(s) of TRSDOS are also buggy, and not helped by the Western Digital FD1771 chip that cannot reliably report its status for several instruction cycles after it receives a command. A common method of handling the delay was to issue a command to the 1771, perform several "NOP" instructions, then query the 1771 for the result. Early TRSDOS neglects the required yet undocumented wait period, and thus false status often returns to the OS, generating random errors and crashes. Once the 1771 delay was implemented, it is fairly reliable. In 1981, Steve Ciarcia published in ''
Byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
'' the design for a homemade, improved expansion interface with more RAM and a disk controller for the TRS-80. A data separator and a double-density disk controller (based on the WD 1791 chip) were made by
Percom Percom Data was an early microcomputer company formed in 1976 to sell peripherals into the emerging microcomputer market. They are best known for their floppy disk systems, first for S-100 machines, and the later for other platforms like the TRS-8 ...
(a Texas peripheral vendor), LNW, Tandy, and others. The Percom Doubler adds the ability to boot and use
double density Disk density is a capacity designation on magnetic storage, usually floppy disks. Each designation describes a set of characteristics that can affect the areal density of a disk or the efficiency of the encoded data. Such characteristics include ...
floppies using a Percom-modified TRSDOS called DoubleDOS. The LNDoubler adds the ability to read and write diskette drives with up to 720 KB of storage, and also the older diskettes with up to 1,155 KB. Near the end of the Model I's lifespan in 1982, upgrades were offered to replace its original controller with a double-density one. The first disk drives offered on the Model I were Shugart SA-400s which supported 35 tracks and was the sole -inch drive on the market in 1977–78. By 1979, other manufacturers began offering drives. Models 3/4/4P uses Tandon TM-100 40-track drives. The combination of 40 tracks and double density gives a capacity of 180 kilobytes per single-sided floppy disk. The use of index-sync means that a "
flippy disk The floppy disk is a data storage and transfer medium that was ubiquitous from the mid-1970s well into the 2000s. Besides the 3½-inch and 5¼-inch formats used in IBM PC compatible systems, or the 8-inch format that preceded them, many propriet ...
" requires a second index hole and write-enable notch. One could purchase factory-made "flippies". Some software publishers formatted one side for Apple systems and the other for the TRS-80. The usual method of connecting floppy drives involves setting the drive letter via jumper blocks on the drive controller board, but Tandy opted for a slightly more user-friendly technique where all four select pins on the drives are jumpered and the ribbon cable is missing the Drive Select line. Thus, the user does not need to worry about moving jumpers around depending on which position on the chain a drive was in. A standard flat floppy ribbon cable is usable on the Model I, in which case the drives is jumpered to their number on the chain, or even an IBM PC "twist" cable, which requires setting each drive number to 1, but only permits two drives on the chain. Although third-party DOSes allow the user to define virtually any floppy format wanted, the "lowest common denominator" format for TRS-80s is the baseline single-density, single-sided, 35-40 track format of the Model I. Third-party vendors like Aerocomp made available double-sided and 80 track -inch and later -inch floppy drives with up to 720 KB of storage each. These new drives are half-height and therefore require different or modified drive housings.


Exatron Stringy Floppy

An alternative to cassette tape and floppy disk storage from Exatron sold over 4,000 units by 1981. The device is a continuous loop tape drive, dubbed the stringy floppy or ESF. It requires no Expansion Interface, plugging directly into the TRS-80's 40-pin expansion bus, is much less expensive than a floppy drive, can read and write random-access data like a floppy drive unlike a cassette tape, and it transfers data at up to 14,400 baud. Exatron tape cartridges store over 64 KB of data. The ESF can coexist with the TRS-80 data cassette drive. Exatron also made a complementary RAM expansion board that installed in the TRS-80 keyboard to increase memory to 48 KB without the EI.


Hard drive

Radio Shack introduced a 5 MB external hard disk for the TRS-80 Model III/4 in 1983. It is the same hard disk unit offered for the Model II line, but came with OS software for Model III/4. An adapter is required to connect it to the Model I's E/I. The unit is about the same size as a modern desktop computer enclosure. Up to four hard disks can be daisychained for 20 MB of storage. The LDOS operating system by Logical Systems was bundled, which provides utilities for managing the storage space and flexible backup. The initial retail price for the first (primary) unit (). Later, a 15MB hard disk was offered in a white case, which can be daisychained for up to 60 MB. Like most hard disks used on 8-bit machines, there is no provision for subdirectories, but the DiskDISK utility is a useful alternative that creates virtual hard disk ".DSK" files that can be mounted as another disk drive, and used like a subdirectory would. To display the directory/contents of an unmounted DiskDISK virtual disk file, a shareware DDIR "Virtual Disk Directory Utility" program was commonly used.


Printers

The "Quick Printer" is an electrostatic rotary printer that scans the video memory through the bus connector, and prints an image of the screen onto aluminum-coated paper in about one second. However, it is incompatible with both the final, buffered version of the Expansion Interface, and with the "heartbeat" interrupt used for the real-time clock under Disk BASIC. This can be overcome by using special cabling, and by doing a "dummy" write to the cassette port while triggering the printer. Two third-party printers were for metal-coated paper, selling for approximately DM 600 in Germany, and a
dot-matrix printer A dot matrix printer is an impact printer that prints using a fixed number of pins or wires. Typically the pins or wires are arranged in one or several vertical columns. The pins strike an ink-coated ribbon and force contact between the ribbon ...
built by
Centronics Centronics Data Computer Corporation was an American manufacturer of computer printers, now remembered primarily for the parallel interface that bears its name, the Centronics connector. History Foundations Centronics began as a division ...
for normal paper, costing at first DM 3000, later sold at approximately DM 1500 in some stores. It has only 7 pins, so letters with descenders such as lowercase "g" do not reach under the baseline, but are elevated within the normal line. Radio Shack offered an extensive line of printers for the TRS-80 family, ranging from basic 9-pin dot matrix units to large wide-carriage line printers for professional use, daisy-wheel printers, ink jet printers, laser printers and color plotters. All have a Centronics-standard interface and after the introduction of the
Color Computer The RadioShack TRS-80 Color Computer, later marketed as the Tandy Color Computer and sometimes nicknamed the CoCo, is a line of home computers developed and sold by Tandy Corporation. Despite sharing a name with the earlier TRS-80, the Color Com ...
in 1980, many also had a connector for the CoCo's serial interface. FP-215 is a flatbed plotter.


Software


BASIC

Three versions of the
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
programming language were produced for the Model I. ''
Level I BASIC Level I BASIC is a dialect of the BASIC programming language that shipped with the first TRS-80, the TRS-80 Model I. Background Tandy-employee Steve Leininger had written the first draft of the NIBL (National Industrial Basic Language) BASIC in ...
'' fits in 4 KB of
ROM Rom, or ROM may refer to: Biomechanics and medicine * Risk of mortality, a medical classification to estimate the likelihood of death for a patient * Rupture of membranes, a term used during pregnancy to describe a rupture of the amniotic sac * ...
, 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''. Level I BASIC is based on
Li-Chen Wang Li-Chen Wang (born 1935) is an American computer engineer, best known for his ''Palo Alto Tiny BASIC'' for Intel 8080-based microcomputers. He was a member of the Homebrew Computer Club and made significant contributions to the software for early ...
's free
Tiny BASIC Tiny BASIC is a family of Programming language#Dialects, flavors and implementations, dialects of the BASIC programming language that can fit into 4 or fewer kilobyte, KBs of random-access memory, memory. Tiny BASIC was designed in response to th ...
with more functions added by Radio Shack. 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". Reviewers praised the manual's quality. Level I BASIC has only two string variables (A$ and B$), 26 numeric variables (AZ), 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 In mathematics, division by zero is division (mathematics), division where the divisor (denominator) is 0, zero. Such a division can be formally expression (mathematics), expressed as \tfrac, where is the dividend (numerator). In ordinary ari ...
, and "SORRY" for
out of memory Out of memory (OOM) is an often undesired state of computer operation where no additional memory can be allocated for use by programs or the operating system. Such a system will be unable to load any additional programs, and since many programs ...
errors. Level I BASIC is not
tokenized In computer science, lexical analysis, lexing or tokenization is the process of converting a sequence of characters (such as in a computer program or web page) into a sequence of ''lexical tokens'' ( strings with an assigned and thus identified ...
; 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 Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
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 William Henry Gates III (born October 28, 1955) is an American business magnate and philanthropist. He is a co-founder of Microsoft, along with his late childhood friend Paul Allen. During his career at Microsoft, Gates held the positions ...
, "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 NewDos/80 is a third-party operating system for the Radio Shack TRS-80 line of microcomputers released in 1980. NewDos/80 was developed by Apparat, Inc. of Denver, Colorado. NewDos/80 version 2.0 was released in August 1981. It ran on the TRS-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, 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). 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

Radio Shack published a combined assembler and program editing package called the Series I Assembler Editor. ''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. Microsoft made its Fortran,
COBOL COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily us ...
and BASCOM
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
compiler available through Radio Shack. In 1982,
Scientific Time Sharing Corporation Scientific Time Sharing Corporation (STSC) was a pioneering timesharing and consulting service company which offered APL from its datacenter in Bethesda, MD to users in the United States and Europe. History Scientific Time Sharing Corporation ( ...
published a version of its APL for the TRS-80 Model III as APL*PLUS/80.


Other applications

Blackjack Blackjack (formerly Black Jack and Vingt-Un) is a casino banking game. The most widely played casino banking game in the world, it uses decks of 52 cards and descends from a global family of casino banking games known as Twenty-One. This fami ...
and
backgammon Backgammon is a two-player board game played with counters and dice on tables boards. It is the most widespread Western member of the large family of tables games, whose ancestors date back nearly 5,000 years to the regions of Mesopotamia and Pe ...
came with the TRS-80, and at its debut Radio Shack offered four payroll, personal finance, and educational programs on cassette. Its own products' quality was often poor. A critical 1980 ''80 Micro'' review of a
text adventure '' Interactive fiction, often abbreviated IF, is software simulating environments in which players use text commands to control characters and influence the environment. Works in this form can be understood as literary narratives, either in the ...
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". The more than 2,000 Radio Shack franchise stores 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. 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".
Broderbund Broderbund Software, Inc. (stylized as Brøderbund) was an American maker of video games, educational software, and productivity tools. Broderbund is best known for the 8-bit video game hits ''Choplifter'', ''Lode Runner'', ''Karateka'', and '' ...
, founded that year, began by publishing TRS-80 software, but by 1983 cofounder
Doug Carlston Douglas Gene Carlston (born April 30, 1947 in Boston, Massachusetts) is the founder and current CEO of Tawala Systems based in San Rafael, California. He was previously CEO, chairman, and co-founder of Broderbund Software, a software publishin ...
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". 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". 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''. 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. Leininger reportedly resigned because he disliked the company's bureaucracy after Tandy's death. 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. The first book authorized by Tandy with technical information on TRSDOS for the Model I did not appear until after the computer's discontinuation. 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 In marketing terminology, a killer application (commonly shortened to killer app) is any computer program or software that is so necessary or desirable that it proves the core value of some larger technology, such as computer hardware, a video game ...
VisiCalc VisiCalc (for "visible calculator") is the first spreadsheet computer program for personal computers, originally released for Apple II by VisiCorp on 17 October 1979. It is often considered the application that turned the microcomputer from a hob ...
. (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.) 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. By 1985, the company's Ed Juge stated that other than
Scripsit Scripsit is a word processing application written for the Radio Shack TRS-80 line of computers. Versions were available for most if not all computers sold under the TRS-80 name, including the Color Computer and several pocket computer designs, as ...
and DeskMate, "we intend to rely mostly on 'big-name', market proven software from leading software firms". A full suite of office applications became available from the company and others, including the VisiCalc and
Multiplan Multiplan is spreadsheet program developed by Microsoft and introduced in 1982 as a competitor to VisiCalc. Multiplan was released first for computers running CP/M; it was developed using a Microsoft proprietary p-code C compiler as part of ...
spreadsheets and the Lazy Writer,
Electric Pencil Electric Pencil, released in December 1976 by Michael Shrayer, was the first word processor for home computers. History In 1975, Michael Shrayer had moved to California after 20 years as a New York filmmaker. Enjoying assembling electronic kits, ...
, and from Radio Shack itself the Scripsit and SuperScripsit word processors. 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 Big Five Software ( Big 5 Software) was an American video game developer in the first half of the 1980s founded by Bill Hogue and Jeff Konyu. The company released games for the Tandy TRS-80 and later the Atari 8-bit family. Most of its TRS-80 ga ...
from producing unlicensed versions of arcade games like Namco's ''
Galaxian is a 1979 fixed shooter arcade video game developed and published by Namco. The player assumes control of the Galaxip starfighter in its mission to protect Earth from waves of aliens. Gameplay involves destroying each formation of aliens, wh ...
'', Atari's ''
Asteroids An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...
'',
Taito is a Japanese company that specializes in video games, toys, arcade cabinets and game centers, based in Shinjuku, Tokyo. The company was founded by Michael Kogan in 1953 as the importing vodka, vending machines and jukeboxes into Japan. It b ...
's ''
Lunar Rescue ''Lunar Rescue'' (ルーナー・ レスキユー Runā Resukyū) is an arcade game released by Taito in November 1979. The gameplay has some resemblance to both Taito's own 1978 hit ''Space Invaders'' and Atari, Inc.'s ''Lunar Lander'' (release ...
'', Williams's '' Make Trax'', and Exidy's '' Targ'' and ''
Venture Venture may refer to: Arts and entertainment Music *The Ventures, an American instrumental rock band formed in 1958 *"A Venture", 1971 song by the band Yes *''Venture'', a 2010 EP by AJR Games * ''Venture'' (video game), a 1981 arcade gam ...
''. Sega's ''
Frogger is a 1981 arcade action game developed by Konami and manufactured by Sega. In North America, it was released by Sega/Gremlin. The object of the game is to direct a series of frogs to their homes by crossing a busy road and a hazardous rive ...
'' and ''
Zaxxon is an isometric shooter arcade game, developed and released by Sega in 1982, in which the player pilots a ship through heavily defended space fortresses. Japanese electronics company Ikegami Tsushinki is also credited for having worked on the de ...
'' were ported to the computer and marketed by Radio Shack. Namco/Midway's '' Pac-Man'' was cloned by Philip Oliver and distributed by Cornsoft Group as ''
Scarfman ''Scarfman'' is a clone of ''Pac-Man'' written by Philip A. Oliver for the TRS-80 computer and published by The Cornsoft Group in 1981. A version for the TRS-80 Color Computer followed in 1982 as ''Color Scarfman'', which uses 64x64 low resolution ...
''. Atari's '' Battlezone'' was cloned for the Models I/III by Wayne Westmoreland and Terry Gilman and published by
Adventure International Adventure International was an American video game publishing company that existed from 1979 until 1986. It was started by Scott and Alexis Adams. Their games were notable for being the first implementation of the adventure genre to run on a m ...
as ''Armored Patrol''. They also cloned ''Eliminator'' (based on ''Defender'') and ''
Donkey Kong is a video game franchise created by Shigeru Miyamoto and owned by Nintendo. It follows the adventures of a gorilla named Donkey Kong (character), Donkey Kong and his clan of other Ape, apes and monkeys. The franchise primarily consists of plat ...
''; the latter wasn't published until after the TRS-80 was discontinued, because
Nintendo is a Japanese Multinational corporation, multinational video game company headquartered in Kyoto, Japan. It develops video games and video game consoles. Nintendo was founded in 1889 as by craftsman Fusajiro Yamauchi and originally produce ...
refused to license the game. Some games originally written for other computers were ported to the TRS-80. ''
Microchess ''Microchess'', by Peter R. Jennings, was the first commercially successful chess program for microcomputers. Originally designed for the MOS Technology KIM-1 it was released on December 18, 1976. ''Microchess'', as small as it was in terms of ...
'' has three levels of play and can run in the 4 KB of memory that is standard with the Model I; the classic ''
ELIZA ELIZA is an early natural language processing computer program created from 1964 to 1966 at the MIT Artificial Intelligence Laboratory by Joseph Weizenbaum. Created to demonstrate the superficiality of communication between humans and machines, ...
'' is another TRS-80 port. Both were offered by Radio Shack. ''
Apple Panic ''Apple Panic'' is a game for the Apple II programmed by Ben Serki and published by Broderbund Software in 1981. ''Apple Panic'' is an unauthorized version of the 1980 arcade game ''Space Panic'', the first game with ladders and platforms. While ...
'', itself a clone of Universal's ''
Space Panic is a 1980 arcade game designed by Universal. Predating Nintendo's ''Donkey Kong'', and lacking a jump mechanic, ''Space Panic'' was the first game involving climbing ladders between walkable platforms. The genre was initially labeled as "climbi ...
'', was written for the TRS-80 by Yves Lempereur and published by Funsoft.
Epyx Epyx, Inc. was a video game developer and publisher active in the late 1970s and 1980s. The company was founded as Automated Simulations by Jim Connelley and Jon Freeman, originally using Epyx as a brand name for action-oriented games before ren ...
s ''
Temple of Apshai ''Temple of Apshai'' is a dungeon crawl role-playing video game developed and published by Automated Simulations (later renamed to Epyx) in 1979. Originating on the TRS-80 and Commodore PET, it was followed by several updated versions for other ...
'' runs slowly on the TRS-80.
Infocom Infocom was an American software company based in Cambridge, Massachusetts, that produced numerous works of interactive fiction. They also produced a business application, a relational database called ''Cornerstone (software), Cornerstone''. ...
ported its series of interactive text-based adventure games to the Models I/III; the first, ''
Zork I ''Zork'' is a text-based adventure game first released in 1977 by developers Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling for the PDP-10 mainframe computer. The original developers and others, as the company Infocom, expande ...
'', was marketed by Radio Shack.
Adventure International Adventure International was an American video game publishing company that existed from 1979 until 1986. It was started by Scott and Alexis Adams. Their games were notable for being the first implementation of the adventure genre to run on a m ...
's text adventures began on the TRS-80, 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'', also by Christopherson, an early
first-person shooter First-person shooter (FPS) is a sub-genre of shooter video games centered on gun and other weapon-based combat in a first-person perspective, with the player experiencing the action through the eyes of the protagonist and controlling the pl ...
''13 Ghosts'' by Software Affair (the Orchestra-80, -85 and -90 people) and shooters like '' Cosmic Fighter'' and '' Defence Command'', and strange experimental programs such as Christopherson's ''Dancing Demon'', in which the player composes a song for a devil and choreographs his dance steps to the music. Radio Shack offered simple graphics animation programs ''Micro Movie'' and ''Micro Marquee'', and ''Micro Music''. Radio Shack offered a number of programming utilities, including an advanced debugger, a subroutine package, and a cross reference builder. Probably the most popular utility package was Super Utility written by Kim Watt of Breeze Computing. 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. Perhaps because of the lack of information on TRSDOS and its bugs, by 1982 perhaps more operating systems existed for the TRS-80 than for any other computer. TRSDOS is limited in its capabilities, since like Apple DOS 3.3 on the
Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-m ...
, 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 Personal Computers, and DoubleDOS, DOSPlus, MicroDOS, UltraDOS (later called Multidos). The DOS for the Model 4 line was originally called TRSDOS Version 6 but was actually produced by and licensed from Logical Systems, and is technically a descendant of the original Model I LDOS. The memory map of the Model I and III render them incompatible with the standard
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initial ...
OS for Z80 business computers, which loads at
hexadecimal In mathematics and computing, the hexadecimal (also base-16 or simply hex) numeral system is a positional numeral system that represents numbers using a radix (base) of 16. Unlike the decimal system representing numbers using 10 symbols, hexa ...
address $0000 with TPA (
Transient Program Area CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initial ...
) 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. ''80 Micro'' magazine published a do-it-yourself CP/M modification for the Model III.


Reception

Dan Fylstra Dan Fylstra is a pioneer of the software products industry. A graduate of the Massachusetts Institute of Technology, in 1975 he was a founding associate editor of ''Byte'' magazine. In 1978 he co-founded Personal Software, and that year reviewed ...
, among the first owners, wrote in ''Byte'' in 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 Pournelle Jerry Eugene Pournelle (; August 7, 1933 – September 8, 2017) was an American scientist in the area of operations research and human factors research, a science fiction writer, essayist, journalist, and one of the first bloggers. In the 1960s ...
wrote in 1980 that "the basic TRS-80 is a lot of computer for the money". He criticized the quality of Tandy's application and system software, and high cost of peripherals. Pournelle reported, however, that with the Omikron board, a customer paid less than $5000 for a computer compatible with TRS-80 and CP/M software "all without building a single kit". Three years later Pournelle was less positive about the computer. He wrote in May 1983, "As to our TRS-80 Model I, we trashed that sucker long ago. It was always unreliable, and repeated trips to the local Radio Shack outlet didn't help. The problem was that Tandy cut corners". Pournelle wrote in July 1983:


Compatible successors

Tandy replaced the Model I with the broadly compatible Model III in 1980. (The
TRS-80 Model II The TRS-80 Model II is a computer system launched by Tandy in October 1979, and targeted at the small-business market. It is not an upgrade of the original TRS-80 Model I, but a new system. The Model II was succeeded by the compatible TRS-80 Mode ...
is an entirely different and incompatible design).


Model III

Tandy released the TRS-80 Model III on July 26, 1980. The improvements of the Model III over the Model I include: built-in lowercase, a better keyboard with repeating keys, an enhanced character set, a real-time clock, 1500-baud cassette interface, a faster (2.03 MHz) Z80 processor, and an all-in-one enclosure requiring fewer cables. A Model III with two floppy drives requires the use of only one electrical outlet; a two-drive Model I requires five outlets.One outlet each for the CPU/keyboard, Expansion Interface, Video Monitor, and the drives. The Model III avoids the complicated power on/off sequence of the Model I. Shortly after the Model III's introduction, Model I production was discontinued as it did not comply with new
FCC The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...
regulations as of January 1, 1981, regarding electromagnetic interference. Tandy distinguished between the high-end Model II and Model III, describing the former as "an administrative system, good for things like word processing, data management and VisiCalc operations" and suitable for small businesses. The lowest-priced version of the Model III was sold with 4 KB of RAM and cassette storage. The computer's CPU board has three banks of sockets (8 sockets to a bank) which take type 4116 DRAMs, so memory configurations come in 16 KB, 32 KB, or 48 KB RAM memory sizes. Computers with 32 KB or 48 KB RAM can be upgraded with floppy disk drive storage. There is space inside the computer cabinet for two full-height drives. Those offered by Tandy/Radio Shack are single-sided, 40 track, double-density (MFM encoding) for 180K of storage. Third-party suppliers offered double-sided and 80-track drives, though to control them they had to modify the TRSDOS driver code or else furnish an alternative third-party DOS which could (see below). The installation of floppy disk drives also requires the computer's power supply to be upgraded. There is no internal cooling fan in the Model III; it uses passive convection cooling (unless an unusual number of power-hungry expansions were installed internally, such as a hard disk drive, graphics board, speedup kit, RS-232 board, etc.). Tandy claimed that the Model III was compatible with 80% of Model I software. Many software publishers issued patches to permit their Model I programs to run on the Model III. Marketing director Ed Juge explained that their designers considered changing from the Model I's 64 column by 16 row video screen layout, but that they ultimately decided that maintaining compatibility was most important. The Model III's memory map and system architecture is mostly the same as the Model I, but the disk drives and printer port were moved from memory mapped to port I/O, thus Model I software that attempts to manipulate the disk controller directly or output to the printer (in particular Model I DOSes and application packages such as Visicalc and Scripsit) will not work. Under the supplied TRSDOS 1.3 operating system Model I disks can be read in the Model III, but not vice versa. The optional LDOS OS (by Logical Systems Inc.) use a common disk format for both Model I and Model III versions. Customers and developers complained of bugs in the Model III's Microsoft BASIC interpreter and TRSDOS. Tandy/Radio Shack (and TRS-80 magazines like ''
80 Micro ''80 Micro'' was a computer magazine, published between 1980 and 1988, that featured program listings, products and reviews for the TRS-80. History Wayne Green, the creator of many magazines such as '' 73'', founded ''80 Microcomputing'' as a ...
'') periodically published many software patches to correct these deficiencies and to permit users to customize the software to their preferences. Differences in the WD1771 and WD1791 floppy controllers created problems reading Model I disks on a Model III (the double-density upgrade in the Model I include both chips while a Model III had only the WD1791). The WD1771 supports four data markers while the WD1791 only supports two, and some versions of TRSDOS for the Model I also use them. In addition, they are used by copy protection schemes. Software was available to allow Model I disks to be read on a Model III. The WD1791 supports the 500 bit/s bitrate needed for high-density floppy drives, but the controller is not capable of using them without extensive modifications. TRSDOS for the Model III was developed in-house by Radio Shack rather than being contracted out like the Model I's DOS. None of the code base from Model I DOS was reused and the Model III DOS was rewritten from scratch; this also created some compatibility issues since the Model III DOS's API was not entirely identical to the Model I DOS. This was primarily to avoid legal disputes with Randy Cook over ownership of the code as had occurred with Model I DOS and also because Radio Shack originally planned several features for the Model III such as 80 column text support that were not included. Two early versions, 1.1 and 1.2, were replaced by version 1.3 in 1981 which became the standard Model III OS. TRSDOS 1.3 is not format compatible with 1.1 and 1.2; a utility called XFERSYS is provided which converted older format disks to TRSDOS 1.3 format (this change is permanent and the resultant disks cannot be read with the older DOS versions). The Model III's boot screen was cleaned up from the Model I. Instead of displaying garbage on screen at power up, it displays a "Diskette?" prompt if a bootable floppy is not detected. The user can insert a disk and press any key to boot. On powerup or reset holding down the key will boot the computer into ROM-based Level II BASIC. This ability is useful if the disk drive is not functioning and cannot boot a TRSDOS disk (or if a boot disk is not available); it permits an operator familiar with the machine hardware to perform diagnostics using BASIC's PEEK and POKE commands. This works for the Model 4 as well, but not for the 4P. While Model I DOS is fairly flexible in its capabilities, Model III DOS is hard coded to only support 180K single sided floppies, a problem fixed by the many third party DOSes. To that end, when Radio Shack introduced hard disks for the TRS-80 line in 1982, the company licensed LDOS rather than attempt to modify Model III DOS for hard disk support. Level II BASIC on the Model III is 16 KB in size and incorporates a few features from Level I Disk BASIC. TRSDOS 1.3 was given a few more minor updates, the last being in 1984, although the version number was unchanged. This includes at least one update that writes an Easter Egg message "Joe, you rummy buzzard" on an unused disk sector, which is reputedly a joke message left by a programmer in a beta version, but accidentally included in the production master. The Model III keyboard lacks . Many application programs use , while others use . Often is used in combination with number and alpha keys. The Model III keyboard also lacks ; to caps-lock the alpha keys the user presses . Under LDOS
typeahead Typeahead is a feature of computers and software (and some typewriters) that enables users to continue typing regardless of program or computer operation—the user may type in whatever speed is desired, and if the receiving software is busy at th ...
is supported. Because TRSDOS 1.3 was found wanting by many users, Tandy offered (at added cost) Logical System's LDOS Version 5 as an alternative. As with the Model I, other third-party sources also offered TRSDOS alternatives for the Model III, including NewDOS, Alphabit's MultiDOS, and Micro Systems Software's DOSPlus. These are compatible with TRSDOS 1.3 and ran the same applications programs, but offer improved command structures, more and better system utilities, and enhancements to the Microsoft BASIC interpreter. After writing the original Model I TRSDOS, Randy Cook began work on his own DOS, titled VTOS, which was superseded by LDOS and also created some frustration for users as it is the only TRS-80 DOS to be copy protected. Although mostly intended as a disk-based computer, the Model III was available in a base cassette configuration with no disk hardware and only 16 KB of RAM with Level II BASIC. Radio Shack also offered a 4K version with Level I BASIC, identical to Model I Level I BASIC, but with the addition of LPRINT and LLIST commands for printer output. Upgrading to a disk machine necessitate installing at least 32 KB of RAM, the disk controller board, and another power supply for the disk drives. Disk upgrades purchased from Radio Shack included TRSDOS 1.3; users upgrading from third-party vendors had to purchase DOS separately (most opted for LDOS or DOSPlus), though a great many Model III applications programs included a licensed copy of TRSDOS 1.3. As with the Model I's E/I, the RS-232C port on the Model III was an extra cost option and not included in the base price of the computer, though the dual disk Model III for $2495 included the serial port. Like the Model I, the Model III sold well in the educational market. Many school administrators valued the Model III's all-in-one hardware design because it made it more difficult for students to steal components. ''InfoWorld'' approved 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." Don French, who had left Radio Shack to found FMG Software after designing the Model I, expressed his disappointment in the new machine while trying to convert CP/M to run on it. "I've encountered numerous problems with the floppy drive and its interface. Radio Shack will sell a Model III to anyone. They're trying to market it as a business computer when the existing software is woefully inadequate. 48K just isn't enough. You run out of memory before you get going. They're selling a medical package that takes up nine disks. I think the Model III is a very poorly conceived machine".


Aftermarket products

Aftermarket hardware were offered by Tandy/Radio Shack and many third-party manufacturers. The usual selection of add-ons and peripherals available for the Model I were offered: outboard floppy drives (one or two could be plugged into a card-edge connector on the back panel), an outboard hard disk drive (LDOS was furnished as Tandy's hard drive OS vice TRSDOS), a high-resolution graphics board (resolution 512 by 192 pixels),The Radio Shack catalog entry advertises 640x240 resolution, but this is a misprint an RS-232C serial port on an internal circuit card, and a parallel printer (connected by a card-edge connector). A popular hardware/software add-on was the Orchestra-90 music synthesizer. It can be programmed to play up to five voices with a range of six octaves stereophonically. A great many Orch-90 (as it was often called) music files were available for download from
CompuServe CompuServe (CompuServe Information Service, also known by its initialism CIS) was an American online service provider, the first major commercial one in the world – described in 1994 as "the oldest of the Big Three information services (the oth ...
. The Orch-90 was licensed from a company called Software Affair, which also produced the Model I-compatible Orchestra-85 from 1981. At least three vendors produced CP/M modifications for the Model III, Omikron (also a Model I mod), Holmes Engineering, and Memory Merchant. Options were available for upgrading the CRT to the CP/M professional standard of 80 columns and 24 rows, as well as eight inch floppy drives. A number of third-party manufacturers specialized in upgrading Model IIIs with high performance hardware and software, and remarketing them under their own labels.It was necessary to rebrand these highly modified Model IIIs because Radio Shack enforced a strict policy that no repair service would be performed on nonstandard RS products. The improvements typically included internal hard disk drives, greater capacity floppy drives, 4 MHz Z80 speedup kits, professional grade green or amber CRT video displays, better DOS software (typically DOSPlus by Micro Systems Software or LDOS by Logical Systems) including the all-important hard drive backup utilities, and custom menu-driven shell interfaces which insulated non-expert users (business employees) from the DOS command line. These were touted as high productivity turnkey systems for small businesses at less cost than competing business systems from higher-end providers such as IBM and DEC, as well as Radio Shack's own
TRS-80 Model II The TRS-80 Model II is a computer system launched by Tandy in October 1979, and targeted at the small-business market. It is not an upgrade of the original TRS-80 Model I, but a new system. The Model II was succeeded by the compatible TRS-80 Mode ...
.


Model 4

The successor to the Model III is the
TRS-80 Model 4 The TRS-80 Model 4 is the last Z80-based home computer family by Radio Shack RadioShack, formerly RadioShack Corporation, is an American retailer founded in 1921. At its peak in 1999, RadioShack operated over 8,000 worldwide stores named Rad ...
released in April 1983. It has faster Z80A CPU, a larger video display 80 columns x 24 rows with reverse video, bigger keyboard, internal speaker, and its 64 KB of RAM can be upgraded to 128 KB of bank-switched RAM. The display can be upgraded with a high resolution graphics card yielding 640240 pixels. The Model 4 is fully compatible with Model III and CP/M application software. A diskless Model 4 (with 16 KB RAM and Level II BASIC) cost , with 64 KB RAM and one single-sided 180K disk drive , and two drives with RS-232C ; an upgrade for Model III owners cost and provided a new motherboard and keyboard. Tandy sold 71,000 in 1984. The Model 4 includes all of the Model III's hardware, port assignments, and operating modes, making it 100% compatible. Model III programs running on a Model 4 can access the Model 4's added hardware features (like 4 MHz clock rate, bigger video screen and keyboard, banked RAM above 64 KB). There were aftermarket software packages that made this ability available to non-programmer users. The Model 4P is a transportable version introduced in September 1983 and discontinued in early 1985. It is functionally the same as the dual-drive desktop model but lacks the card edge connector for two outboard diskette drives and for cassette tape interface. It has a slot for an internal modem card and could emulate a Model III. The Model 4D with bundled Deskmate productivity suite was introduced in early 1985. It has a revised CPU board using faster gate array logic which includes the floppy controller and RS-232C circuitry, all on a single board. The computer has two internal double-sided diskette drives, and is the last model descended from the 1977 Model I. It retailed for at its introduction in 1985. During 1987–1988 the retail stores removed the Model 4Ds from display but they were available by special order through 1991.


See also

*
List of TRS-80 games This list contains video games created for the monochrome 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 ...
*
List of TRS-80 software The TRS-80 series of computers were sold via Radio Shack & Tandy dealers in North America and Europe in the early 1980s. Much software was developed for these computers, particularly the relatively successful Color Computer I, II & III models, wh ...
*
List of TRS-80 clones The following is a list of clone (computer science), clones of Tandy Corporation, Tandy's TRS-80 model I and III home computers: * Aster CT-80 by Aster CT-80#The company, Aster b.v. * DGT-100 and DGT-1000 by Digitus * D8000, D8001 and D8002 by Di ...
* '' SoftSide'', magazine with BASIC programs for the TRS-80 and other microcomputers * '' The Alternate Source Programmer's Journal'', TRS-80 magazine with technical programming articles


Note


References


Further reading

* *


External links

*
Radio Shack Catalog Archive (1939–2011)



trs-80.com : Ira Goldklang's TRS-80 Revived Site

TRS-80 Model 1 at www.old-computers.com

REM 80 – The North West TRS-80 USers Group Magazines


* ttp://jtandy.retrolandia.net/ jTandy, another javascript TRS-80 emulator : online emulation of Model III BASIC & commercial arcade games
Tandy Model 4/4P Technical Reference

LDOS 5.1 User Manual

''Byte'' magazine review of LDOS 5.1
* {{Authority control Z80-based home computers Home computers Computer-related introductions in 1977 Products introduced in 1977 8-bit computers Early microcomputers Products and services discontinued in 1981