anyone use the IBM 1620 computer?

[DGM]

I was in High School in the early 1970s. Our school had a 1620, the only one in the country with two hard disk drives, we were told. It was donated to the school by the county, with the proviso that they could come in occasionally (not during class) to run a payroll (disaster recovery testing, I think).

Our class was Fortran (II-D) programming. We had an 80-column card punch to write our programs on, and a line printer, as well as an IBM Selectric typewriter on the console. There was magnetic tape I/O as well. I wrote programs to do integration, calculate square roots (using my own method of approximation to give as many decimals as you wanted; I used variable names relating to Tarzan stories so I was pretty cool - what happened to me?), figure out how much money I could retire on if I invested my Social Security payment instead of giving it to the government (working for $25,000 per year for 40 years, which seemed like a lot of money at the time).

Our teacher was pretty cool and taught math as well (I was taking Calculus). One time he brought in a tape full of machine code programs - GAMES! The best one was a reaction-time program that would type "random" letters on the typewriter. When an X came up, it would stop and wait for the Enter key to be pressed and output the reaction time, which was about .1 or .2 seconds at first.

There were lights on the console showing a register in binary notation, and I noticed that, just before it typed the X, the lights would change. My reaction time really improved after that and I wowed the teacher with times in the low hundredths of a second (I don't think we told him why I was so good).

The computer had core memory - little magnetic doughnuts strung in a grid of wires. I don't remember how much memory it had, or the capacity of the hard drives (they had several platters). It was a great learning experience, though.

I was hoping someone would ask about this, when the other thread mentioned it.