May the Circle be Unbroken

Two weeks ago my career in IT came full circle. Fifty-five years ago, as a rising high school senior, I took a summer course in computers at Columbia University in NYC. It was a very comprehensive course which covered theories of computing, algorithms, compilers, etc. in the mornings and then taught us programming in Fortran and assembler for Columbia’s newly updated IBM 7094 computer in the afternoons. For many years, that course was my only formal training in computers and IT. Most of what I have learned since then was either self-taught or learned on the job.

The 7094 had recently been updated from a 7090. The hottest question at the time was what was the difference between a 7090 and a 7094, and the answer was 4. In addition to a few other changes in clock speed, instruction set, etc. a major change between the two computers was that the 7094 had 4 more index registers. The 36 bit instructions for these computers had 3 Tag bits set aside to indicate the use of an index register, often used for stepping through memory in loops. In the 7090 these 3 bits selected one of 3 index registers. For the 7094, a binary decoder circuit was added so that the 3 bits could select one of 7 index registers, thus the update from 7090 to 7094.

Part of my decision to take a course in computers during that summer was the news that my high school, Brooklyn Technical High School, was planning to get a new IBM 1130 computer in the fall. In addition to taking the course at Columbia that summer I also went to the IBM offices on Maiden Lane in lower Manhattan and bought a set of manuals for the IBM 1130 so that I would be ready to use the computer when it arrived. In fact, I ended up being the first person to successfully run a program on Tech’s 1130. My oldest brother was going to school at Brooklyn College at the time, and was working on the IBM 1620 which they had there. I was able to visit his office and use a keypunch machine there to punch my program onto the punch cards then used as input for computers. As I recall, the program was to calculate great-circle bearings from NYC to other points on the globe. My father was a ham radio operator and he had installed a large, rotatable antenna on a tower alongside our home in Queens. He asked me to give him a table of bearings to point his antenna depending on where in the world he wanted to speak to someone, so I wrote the program, punched it onto cards at Brooklyn College (along with the Monitor Control Records, an early form of JCL for the 1130) and then walked into the computer room at Brooklyn Tech one day and asked the teacher there, I believe it was the head of the electronics course, if I could use the computer. He stared in amazement as I walked over to the card reader, inserted my card deck and then proceeded to run the program which generated many pages of output tables. He was sufficiently impressed by my ability to get the computer working that from that day on I was always welcome to come into the computer room, even if I was cutting a class to do it.

One interesting sideline about the 1130 was that it was a desk-sized computer console with a removable rotating magnetic disk cartridge (IBM 2315) behind a panel in the desk stand. The monitor program, as well as the compiler and other utilities were loaded onto the disk drive from 2 boxes of punched cards (about 4000 total cards). One item which I seem to have neglected to notice in the manuals I bought was that you had to turn off the disk drive with a switch behind the front panel before you shut off the computer. Otherwise, the retracting head of the magnetic drive would scribble all over the disk as the power was removed. We wondered why we had to load the 2 boxes of cards onto the magnetic drive every day, until someone realized that the switch inside the front panel would save us that chore.

There is irony in the fact that this IBM 1130 was bigger and more powerful than the IBM 1620 computer at the college I went to, although my college also managed to purchase an IBM 1130 during the summer before my senior year. More about that in another post.

The full circle I was talking about in the first paragraph of this post is that 2 weeks ago I started working as a system administrator in the computer research facility of the computer science department at Columbia. So my career in computing, which started with a course at Columbia 55 years ago, has now returned me to Columbia.