TRS-80 Model 100



The TRS-80 Model 100 is a notebook computer introduced in 1983. It is one of the first notebooks with a keyboard and LCD display, in a battery case of the size and the shape of a notebook. It was manufactured by Kyocera and originally sold in Japan as 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 has become one of the most popular models of the company, with more than 6,000,000 units sold worldwide. The Olivetti M-10 and NEC PC-8201 and PC-8300 were also built on the same Kyocera platform, with differences in design and hardware. It was originally marketed as the Micro Executive Workstation (MEWS), although the term was not adopted and was eventually dropped.

The 8K and 24K versions sold for $ 1,099 and $ 1,399, respectively. The Model 100 has been promoted as being able to operate 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. The only form of mass storage available on the computer was wearing an audio cassette recorder, which was notoriously difficult and unreliable. Many times, several attempts to read a tape were needed, with a lot of volume adjustment. A popular alternative was the Tandy Portable Disk Drive (TPDD), a serial device capable of storing 100 KB of data on a 3.5-inch floppy disk; this reader is identical to the Brother FB100 reader for knitting machines. A second version, the TPDD2, can store up to 200 KB because it uses both sides of double-sided disks. A disk / video interface expansion box was launched in 1984, with a 5-1 / 4 inch 180KB duplex disc player and a CRT video adapter. This allowed Model 100 to display a 40- or 80-column video on an external TV or video monitor. An empty drive bay allowed the installation of a second disk drive (which proved useful for backing up the disks). Another popular form of data backup was the transfer of files to a desktop computer, either via the modem connected to a telephone line or via the RS-232 serial port connected to a null modem cable. TELCOM’s built-in firmware has made it a convenient option. The TRSDOS 6 operating system of the TRS-80 Model 4 included a utility called TAPE100 that used the Model 4 cassette port to read and write tapes created by a Model 100, whose data was stored in TRSDOS disk files. Also because TRSDOS 6 included a communication application (COMM / CMD), the Model 100 proved to be a popular “device” for the Model 4 client. A barcode scanner stick was also offered.

When first switched on, the Model 100 displays a menu of applications and files and the date and time. 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. 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. 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> 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. 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”. 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. 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.



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