TRS-80 Model 100

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TRS-80 Model 100
Radio Shack TRS-80 Model 100.jpg
DeveloperKyocera, Tandy, Microsoft
TypePortable computer
Release date1983; 38 years ago (1983)
Introductory price8K version US$1,099 (equivalent to $2,860 in 2020)
24K versions US$1,399 (equivalent to $3,640 in 2020)
Units sold6 million
Operating systemCustom dedicated runtime in firmware
CPU2.4 MHz Intel 80C85
MemoryKB - 32 KB (supported)
Display8 lines, 40 characters LCD
Graphics240 by 64 pixel addressable graphics
InputKeyboard:56 keys, 8 programmable function keys, and 4 dedicated command keys
PowerFour penlight (AA) cells, or external power adapter 6V (>180 mA)
Dimensions300 by 215 x 50 mm
MassAbout 1.4 kg (3.1 lb) with batteries

The TRS-80 Model 100 is a portable computer introduced in 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 large book.

It was made by Kyocera, and originally sold in Japan as the Kyotronic 85. Although a slow seller for Kyocera, the rights to the machine were purchased by Tandy Corporation. The computer was sold through Radio Shack stores in the United States and Canada and affiliated dealers in other countries. It became one of the company's most popular models, with over 6 million units sold worldwide. The Olivetti M-10 and the NEC PC-8201 and PC-8300 were also built on the same Kyocera platform, with some design and hardware differences. It was originally marketed as a Micro Executive Work Station (MEWS),[1] although the term did not catch on and was eventually dropped.


The internals of the TRS-80 Model 100. The left half is the back.
  • Processor: 8-bit Oki 80C85, CMOS, 2.4576 MHz
  • Memory: 32 kB ROM, 8, 16, 24, or 32kB static RAM. Machines with less than 32 kB can be expanded in 8 kB increments of plug-in static RAM modules. An additional 32 kB Option ROM can be installed, for a total of 64 KB of ROM (bank-switched in a 32 KB aperture), and the Standard ROM is socket-mounted (not soldered-in) so is readily replaceable.
  • Display: 8 lines, 40 characters LCD, twisted nematic (gray) monochrome, with 240 by 64 pixel addressable graphics. The screen is reflective, not backlit.[2] The screen was made by Sharp Electronics.[3] The LCD controllers are by Hitachi: (10) HD44102CH column controller ICs and (2) HD44103CH row driver ICs; the HD44102CH's provide the programmable hardware interface to software. The refresh rate is about 70 Hz (coarsely regulated by an R-C oscillator, not a crystal).
  • Keyboard: 56 keys, QWERTY layout with full standard spacing, 8 programmable function keys, 4 dedicated command keys. These last 12 are tactile "button"-style keys. Almost all keys other than the 12 function keys are capable of rollover (without phantom keys appearing depressed), so multi-key combinations can be used.
  • Peripherals: The basic unit includes: Built-in 300 baud telephone (POTS) modem (North American versions), Centronics-compatible parallel printer port, RS-232 serial communication port (sharing serial I/O chip with internal modem), barcode reader input, cassette audio tape I/O, real-time clock.
  • Expansion: System bus interface DIP socket (under a cover on the bottom of the machine).
  • Dimensions: 300 by 215 x 50 mm, weight about 1.4 kilograms (3.1 lb) with batteries

Power supply: Four penlight (AA) cells, or external power adapter 6V (>180 mA, tip negative configuration)

The 8K and 24K versions sold for US$1,099 and US$1,399 respectively.[4]

The Model 100 was promoted as being able to run up to 20 hours and maintain memory up to 30 days on a set of four alkaline AA batteries. It could not run from the rechargeable nickel-cadmium batteries available at the time, but a hardware modification was available that made this possible.[citation needed]

The computer's only available form of mass storage was the port for a cassette audiotape recorder, which was notoriously finicky and unreliable. Many times several attempts to read a tape were required, along with much adjustment of the volume setting.[citation needed][dubious ]

A popular alternative was the Tandy Portable Disk Drive (TPDD),[5] introduced in 1986, a serial device capable of storing 100 KB of data on a 3.5-inch single-sided double-density diskette;[6][7] this drive is identical to the Brother FB100 drive for knitting machines.[8][9] A second version, the TPDD2,[10] can store up to 200 KB.

A Disk/Video Interface expansion box was released in 1984, with one single-sided double-density 180KB 5-1/4 inch disk drive and a CRT video adapter. This allowed the Model 100 to display 40 or 80 column video on an external television set or video monitor. One empty drive bay permitted the installation of a second disk drive (which proved handy for backing up disks).[11]

Another popular form of data backup was that of file transfer to a desktop computer, via either the modem connected to a telephone line, or the RS-232 serial port connected to a null modem cable. The built-in TELCOM firmware made this a convenient option. Not coincidentally, the TRS-80 Model 4's TRSDOS 6 operating system included a utility called TAPE100 that used the Model 4's cassette port to read and write tapes created by a Model 100, the data of which were stored in TRSDOS disk files. Also because TRSDOS 6 included a communications application (COMM/CMD), the Model 100 proved a popular "peripheral" for the Model 4 customer.

A bar code reader wand was also offered.

ROM firmware[edit]

When first switched on, the Model 100 displays a menu of applications and files and the date and time.[12] The ROM firmware-based system boots instantly, and the program that was running when the unit was powered off is ready to use immediately on power-up. Cursor keys are used to navigate the menu and select one of the internal or added application programs, or any data file to be worked upon.

The 32 kilobyte read-only memory of the Model 100 contains the N82 version of the Microsoft BASIC 80 programming language. This is similar to other Microsoft BASICs of the time and includes good support for the hardware features of the machine: pixel addressing of the display, support for the internal modem and serial port, monophonic sound, access to tape and RAM files, support for the real-time clock and the bar code reader, and I/O redirection between the machine's various logical devices. Like previous Microsoft BASIC interpreters, variable names were restricted to two characters and all program lines and subroutines were numbered and not named. However, the default for floating point numbers is double-precision. This was reportedly the last application software with code written by Bill Gates.

The ROM also contains a terminal program, TELCOM; an address/phone book organizer, ADDRSS; a to-do list organizer, SCHEDL; and a simple text editor, TEXT. The TELCOM program allows automation of a login sequence to a remote system under control of the BASIC interpreter.[12] As with other home computers of the era, a vast collection of PEEK and POKE locations were collected by avid hobbyists.

The Model 100 TEXT editor was noticeably slow in execution, especially for fast touch typists. This was due partly to the slow 8085 CPU and due partly to the slow response time of the LCD screen. Often after speed-typing a sentence or two, the user would have to wait several seconds for the computer to "catch up". As a small compensation, many users found it somewhat amusing watching the text appearing on the display, particularly text inserted into the body of a paragraph.

A perhaps not well-known but documented feature of TEXT was that it partially supported the WordStar command interface. The supported commands were the cursor movement and character deletion <Control><alpha> key combinations on the left hand side of the keyboard; the commands for activating Wordstar menus, like the <Ctrl><K> Block menu, were not functional.

Invisible files in the system RAM named "Hayashi" and "Suzuki" commemorate the names of designers Junji Hayashi and Jay Suzuki. Another invisible deleted file named "RickY" refers to Rick Yamashita.[13] The Model 100 firmware was the last Microsoft product that Bill Gates developed personally, along with Suzuki. According to Gates, "part of my nostalgia about this machine is this was the last machine where I wrote a very high percentage of the code in the product".[14][12]

Added applications and data files are stored in the internal battery-backed RAM; these can be loaded from and stored to an audio cassette tape recorder or external floppy disk drive. Optional ROMs can be installed in the Model 100, providing a range of customized application software.[12] Only one optional ROM can be installed at a time. Some commercial software applications for the Model 100 were also distributed on cassette.

The Model 100 ROM has a Y2K bug; the century displayed on the main menu was hard-coded as "19XX". Workarounds exist for this problem. Since the century of the date is not important for any of the software functions, and the real-time clock hardware in the Model 100 does not have a calendar and requires the day of the week to be set independently of the date, the flaw does not at all impair the usability of the computer; it is cosmetic.


When introduced, the portability and simplicity of the Model 100 made it attractive to journalists,[15][16][17] who could type about 11 pages of text and then transmit it for electronic editing and production using the built-in modem and TELCOM program.

The keyboard is full-size and uses a standard (QWERTY) layout; reviewers praised it but reported that it was noisy.[12] To quiet the computer, owners put orthodontic rubber bands under the keys.[16] The computer is otherwise silent when it operates, except for the speaker, and runs for 20 hours on 4 readily available and easily replaceable AA batteries. Data is protected by a built-in rechargeable (Ni-Cd) battery when the AA batteries discharge or are removed for replacement. There are several simple programs available on the Internet for transferring files between a Model 100 and a modern personal computer (or a vintage one).

The Model 100 was also used for industrial applications and in science laboratories as a programming terminal for configuration of control systems and instruments. Its compactness (ease of handling and small space requirements), low maintenance needs, lack of air vents (a plus for dusty or dirty environments), full complement of ports, and easy portability made it very well suited for these applications.

Third-party peripherals for the Model 100 extended its battery life and file storage capacity. Software was designed, and is still available, to extend the display capabilities (to 60 columns and 10 rows of text using smaller characters) and to provide more advanced word-processing or calculation software than the supplied programs. To this day, hobbyists continue to design games, applications, and hardware for this device. Simple drawing programs and games using the pixel-addressable display were favorites among users. As with virtually all other contemporary home computers, users are able to create their own applications using the included BASIC programming language. There are no built-in facilities for 8085 assembler programming, but the thoroughly-documented BASIC interpreter by Microsoft offered the clever coder tricks for accessing machine code subroutines. These tricks usually involved packing the raw object code into strings or integer arrays, and would be familiar to veteran programmers for the older TRS-80 Models I and III.

Peers and successors[edit]

A Tandy 102 portable and 200 laptop

The Tandy 200[18][19] was introduced in 1984 as a more capable sister product of the Model 100. The Tandy 200 has a flip-up 16 line by 40 column display and came with 24 KB RAM which can be expanded to 72 KB (3 banks of 24 KB). Rather than the "button" style keys of the Model 100, its four arrow keys are a cluster of keys of the same size and shape as those comprising the keyboard, though the function and command "keys" are still of the button type. The Tandy 200 includes Multiplan, a spreadsheet application. It also added DTMF tone dialing for the internal modem, whereas the Model 100 only supports pulse dialing. On a phone line that doesn't support pulse dialing, users may dial manually using a touch-tone phone and then put the Model 100 online.

The last new model that could be considered part of this line was the Tandy 600,[20][21] introduced in October 1985. Similar to the Tandy 200, it features a flip-up screen, but with 80 columns rather than 40. Built-in features include a 3.5" diskette drive, rechargeable batteries, and 32K of RAM expandable to 224K. The underlying software platform was Microsoft's 16-bit Hand Held Operating System (Handheld DOS or HHDOS), along with word processing, calendar, database, communication and spreadsheet software. Unlike earlier models, BASIC was an extra-cost option rather than built in.[22]

The last refresh to the product line was the Tandy 102, introduced in 1986 as a direct replacement for the Model 100, having the same software, keyboard, and screen, and a nearly identical, but thinner, form factor that weighed about one pound less than the Model 100. This reduction in size and weight was made possible by the substitution of surface-mount chip packaging. Standard memory for the Model 102, 24K RAM, was upgradable to 32K with an ordinary 8K SRAM chip.

Later portables from Tandy no longer featured a ROM-based software environment, starting with the Tandy 1400LT, which ran a diskette-based MS-DOS operating system.

Similar computers from other companies[edit]

The NEC PC-8201 computer

The Olivetti M-10 and the NEC PC-8201 and PC-8300 were built on the same platform as the original Kyocera design. The earlier and smaller Epson HX-20 of 1983 used a much smaller LCD display, four lines of twenty characters, and had an internal cassette tape drive for program and file storage. There were several other "calculator-style" computers available at the time, including the Casio FP-200, the Texas Instruments CC-40, and the Canon X-07.[23]

Systems of about the same size and form-factor as the Model 100, aimed at journalists, were sold by companies such as Teleram, as the Teleram T-3000[24] and GRiD Systems, as the GRiD Compass, which was used by NASA. GRiD was later acquired by Tandy. The Bondwell 2 of 1985 was a CP/M laptop in a similar form factor to the Model 200. Convergent Technologies released the WorkSlate in late 1983 which similarly targeted mobile computing.

Computers from two other British companies were similar in form and functionality to the Model 100. The Cambridge Z88 of 1987, developed by British inventor Sir Clive Sinclair, had greater expansion capacity due to its built-in cartridge slots. It had a far more sophisticated operating system called OZ that could run multiple applications in a task-switched environment. The firmware contained a powerful application called Pipedream that was a spreadsheet that could also serve capably as a word processor and database. The other British computers were the Amstrad NC100 and NC200, produced from 1992.

The electronic word processing keyboards AlphaSmart Dana and the Quickpad Pro bear some resemblance to the physical format of the TRS-80 Model 100. In Japan, Pomera still makes and sells dedicated word processors under model names Pomera DM100, Pomera DM200 etc.

The Laser 50 educational computer is in the same size and form factor as the Model 100, and was sold by Video Technology.


Tandy stated that the Model 100's sales "have only been moderate",[25] and an InfoWorld columnist later claimed that "it was only journalists" who had been buying it.[26] The system's popularity with journalists, however, probably helped Radio Shack improve the company's poor reputation with the press and in the industry.[25] The magazine's reviewer called the computer "remarkable", praising its power relative to size and price and noting that he wrote the review "at the lofty height of 37,500 feet aboard a United DC-10". He concluded, "I'm not used to giving Radio Shack kudos, but the Model 100 is a brave, imaginative, useful addition to the realm of microcomputerdom" and "a leading contender for InfoWorld's Hardware Product of the Year for 1983",[27] an award which it indeed won.[16]

BYTE described the Model 100 as "an amazing machine". While noting the lack of mass storage, the reviewer praised "one of the nicest keyboards I've used on any machine, large or small" and the "equally impressive" built-in software, and concluded "the designers of this machine ... should be congratulated".[12] The magazine later stated that "Tandy practically invented the laptop computer".[28] PC Magazine criticized the Model 100 display's viewing angle, but noted that the text editor automatically reflowed paragraphs unlike WordStar. It concluded that the computer "is an ingenious, capable device ... an exciting example of the new wave of portable computers".[29] Creative Computing said that the Model 100 was "the clear winner" in the category of notebook portables under $1000 for 1984, although cautioning that "the 8K version is practically useless".[30]


  • VirtualT An open source Model 100/102/200 emulator with an integrated debugger, hardware access utilities and a complete FX-80 printer emulation.
  • CloudT A Model 100 emulator implemented as a mobile and desktop "web app" that runs in a browser.

Aftermarket products[edit]

  • DLPilot - allows a Palm OS PDA with a serial port to emulate a Tandy TPDD drive, providing affordable, compact, and portable storage that is easily synced to a desktop computer
  • ReMem - replaces all the memory in the laptop, allowing the use of 4MB of flash ROM and 2MB of SRAM
  • REX - memory subsystem that fits in the option ROM socket
  • Tandy 200 RAM Module - adds 2 banks of 24kb to a T200
  • NADSBox - New Age Digital Storage Box - Interfaces an SD media card using the Tandy TPDD drive protocol for portable storage and easy file transfers to a desktop computer using industry-standard FAT-formatted Secure Digital cards.
  • PCSG's SupeROM - WriteROM word processor; FORM spreadsheet input template; LUCID spreadsheet; Database (relational); Thought outliner.


  1. ^ "Radio Shack Computer Catalog RSC-10, page 59". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved April 10, 2017.
  2. ^ The display hardware is pure graphics; character display is generated by software, and the 8x40 character format is a characteristic of the standard ROM software (which, incidentally, is socketed and replaceable).
  3. ^ InfoWorld Jan 23, 1984 Sharp's 25-line display for lap models due out soon, Tom Shay
  4. ^ "The Micro Executive Workstation(TM)". Radio Shack 1984 Catalog. Tandy Corporation. 1984. p. 59. Retrieved January 8, 2008.
  5. ^ "Radio Shack Computer Catalog RSC-15, page 50". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved April 11, 2017.
  6. ^ Portable Disk Drive Operation Manual, Cat. No. 26-3808, 1985, TANDY
  7. ^ Tandy Portable Disk Drive (PDD1 and PDD2)Command Reference
  8. ^ brother fb-100 wiki
  9. ^ Brother FB100 Floppy Drive User Guide, Machine Knitting etc
  10. ^ "Radio Shack Computer Catalog RSC-17B, page 42". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved April 11, 2017.
  11. ^ "Radio Shack Computer Catalog RSC-12, page 59". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved April 10, 2017.
  12. ^ a b c d e f Malloy, Rich (May 1983). "Little Big Computer / The TRS-80 Model 100 Portable Computer". BYTE. p. 14. Retrieved October 19, 2013.
  13. ^ Akira Kogawa (October 28, 2005). "The Bill Gates I Know, Volume 12" (in Japanese). Retrieved January 8, 2008.[permanent dead link] Title and author obtained via Google translation from the original Japanese.
  14. ^ Gates, Bill. "Bill Gates Interview". National Museum of American History, Smithsonian Institution (Interview). Interviewed by David Allison. Retrieved April 10, 2013.
  15. ^ Bruce Garrison Computer-assisted reporting, Routledge, 1998 ISBN 0-8058-3021-9 , page 192
  16. ^ a b c Robinson, Dan (May 13, 1985). "Making a Good Thing Better". InfoWorld. pp. 46–47. Retrieved February 1, 2015.
  17. ^ Kennedy, Maev; Holborn, Margaret (September 21, 2012). "Guardian's first laptop - podcast: teaching resource from the GNM Archive October 2012". The Guardian. Retrieved February 5, 2015.
  18. ^ "Radio Shack Computer Catalog RSC-15, page 51". Radio Shack Catalogs dot com. Tandy/Radio Shack. Retrieved April 11, 2017.
  19. ^ "A Star is Born, Tandy advertisement in 80 Micro magazine, April 1985". www.archive dot org. Tandy Corp. Retrieved July 9, 2020.
  20. ^ Dixon, Bradford N. "Tandy's Model 600, 80 Micro magazine, March 1986, page 28". www.archive dot org. CW Communications. Retrieved July 9, 2020.
  21. ^ "Tandy advertisement for Model 600". www.archive dot org. Tandy Corp. Retrieved July 9, 2020.
  22. ^ "The Tandy 600 FAQ - Version 3". DigitalDinos. May 26, 2008. Archived from the original on October 13, 2008. Retrieved February 22, 2009.
  23. ^ 14 notebook computers in brief: Creative Computing Vol 10 No 1, January 1984
  24. ^ The Portable Companion, June/July 1982
  25. ^ a b Bartimo, Jim (August 20, 1984). "Radio Shack Polishes Its Image". InfoWorld. IDG. pp. 47–52. Retrieved February 28, 2011.
  26. ^ Strehlo, Kevin (June 17, 1985). "The Chiclet Rule and the Green Dragon". InfoWorld. p. 8. Retrieved March 24, 2016.
  27. ^ Hogan, Thom (June 27, 1983). "TRS-80 Model 100, battery-run, briefcase micro". InfoWorld. pp. 66–69. Retrieved January 31, 2015.
  28. ^ Malloy, Rich; Vose, G. Michael; Stewart, George A. (October 1987). "The Tandy Anniversary Product Explosion". BYTE. p. 100. Retrieved August 4, 2014.
  29. ^ Sandler, Corey (June 1983). "The TRS-80 Model 100: Never An Idle Moment". PC Magazine. p. 195. Retrieved October 21, 2013.
  30. ^ Ahl, David H. (December 1984). "Top 12 computers of 1984". Creative Computing. Retrieved March 16, 2019.
  • TRS-80 Model 100 Owner's Manual, (1983) Tandy Corporation, Fort Worth Texas
  • BYTE Magazine April 1984, advertisement for Disk-Video Interface
  • BYTE Magazine May 1985, advertisement for Model 200
  • Rich Malloy, "Little Big Computer: The TRS 80 Model 100 Portable Computer", BYTE magazine, May 1983 pg. 14 - 34
  • Stan Wszola, "NEC PC 8201 Portable Computer", BYTE magazine June 1983, pg. 282

External links[edit]