Home — Computers

Computers I Have Known

Disclaimer: I have run through half of my allotted three-score-and-ten, and time has eroded memories. Facts that I'm not certain about are marked with (?).

Learning to crawl

My first experience with computers was with the listings and IBM flowcharting templates my father would bring home from the Martin Marietta plant in Middle River, MD. Sometimes he would take me to the large machine room. I remember the modems as large as VCRs, and the bit STOP button on the console of the IBM 360. "If there's an emergency, someone pulls it, and then they fire him," he would say.

Learning to walk

In the mid 1970's we were one of the minions who constructed the "TV typewriter" described in a popular electronics magazine. It was meant to be the terminal for a computer we would eventually build. The computer, 8080-based, was built with a custom-designed bus and memory cards, and sported a front panel rescued from an abandoned IMSAI. There was no other input and output was a 7-segment LED. I was handed the coding manual for the 8080 and told to develop a floating point library. I had no idea what floating point was and the project never was finished.

In the summer of 1978, a Teletype Model 33 and a home-brew Tarbell cassette tape interface were added. The loan of an S-100 based system with CP/M enabled us to develop in assembler, and we ported Palo Alto Tiny Basic to our little system. I hacked PATB to add bitwise boolean operations, thereby learning how to build a recursive descent parser in less than 1K. The same code served as the basis for a text editor. (All early computers had their idiosynchrocies and ours was no exception. The Teletype sometimes issued spurious @s, so my text editor had an option to ignore them or treat them as spaces.)

The next year, we acquired two 8" floppies and installed CP/M on the system. This allowed us to acquire BDS C and other advanced development tools. (BDS stands for Brain Dead Software. As I recall, the creator flunked out of med school and started selling his compiler to finance a second go.) My father got a Pascal compiler together by typing the assembly code for it from a book. I used the compiler to develop a disassembler for a Texas Instruments programmable calculator, with the aim of studying the library programs that came with the calculator.

Later additions included an ADDS Viewpoint terminal (it had a sleek black keyboard) and a Diablo dot matrix printer. We upped the RAM to 64K and exploited the RAM disk capability to speed the assembler. We obtained VEDIT and I spent several days configuring shortcut keys on the ADDS to work with it. We obtained WordStar but I used it only for term papers. When I did German work I had to add the umlauts and ß's with a pen.

While I was in college, we salvaged an NCR 5100 (?) from the slag heap. This machine had a custom keyboard (with a key for entering double zeros) and CP/M on a 20" (?) hard disk. At school, we had the option of running assignments on a shared terminal or in batch, an one of several self-service punch/reader stations. I used batch almost exclusively to avoid waiting for terminals. At that time we were taught to use SPICE, a venerable circuit analysis program. I wrote a stripped-down version of it for our machine at home, this being my first (and only) non-trivial Fortran project.

Learning to drive

After leaving college I found myself without a computer until we dug up a used ALSPA, a Z80 with 64K, and a Hazeltine terminal. The Hazeltine used a tilde instead of ESC as a control leader, which meant that you had to use the trigraphs to write C.

From 1986-87 I was employed at the Johns Hopkins School of Medicine. We had IBM PC XTs (10 MB HD, EGA). I programmed several workflow applications in R:BASE. Our group managed the correspondence and teaching documents for the pediatric group. Although all new work as done in WordPerfect, we had a good deal of legacy documents on an IBM DisplayWrite. We also had the PC DisplayWrite emulator and the first PC release of Microsoft Word. I was one of the first to purchase the Mix C compiler which I used to develop a diskette cataloging utility and an interpreter for the Bloop and Floop languages in GEB.

More memories to come, including one of my father's first computers.

Home