anyone use the IBM 1620 computer?

[Don Shepherd]

I've been reading a couple of books about this computer from the late 1950's, using the decimal system instead of binary. It was a relatively small computer, designed for small businesses and colleges and universities who could afford it.

Has anyone used this system, and if so what are your thoughts about it and experience with it?

[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.

[Paul Berger (Canada)]

According to a book I have handy about IBM's early (pre-360) computers it initially had 20,000 digits of core and it was later increased to 60,000 digits. Each digit occupied 6 bits. It would seem likely that the disks would have been the IBM 1311 which was their first disk product with removable packs. the 1316 disk pack used in that drive had six 14" platters with a total capacity of 2 million characters. Disk storage was only available on a faster version of the 1620 introduced in 1962.

[Don Shepherd]

Thanks DGM, those must have been great experiences.

Tarzan-related FORTRAN variable names. Let's see: JANE (obviously), BOY, UMGAWA, that chimp's name I forget. "ahhyeeeaaahyeeaaah" (invalid, too many characters).

One interesting thing I discovered while reviewing the 1620 books: raising a number to a power in FORTRAN (**) was called "involution." I've never heard that term before.

[DGM]

I remember using TARZAN, KNIFE and JANE AT least. Variables starting with I thru L? could be used as loop counters (integers) and others were real numbers. Wish I still had the code...

[toml_12953]

(03-29-2019 01:13 AM)Don Shepherd Wrote:  Thanks DGM, those must have been great experiences.

Tarzan-related FORTRAN variable names. Let's see: JANE (obviously), BOY, UMGAWA, that chimp's name I forget. "ahhyeeeaaahyeeaaah" (invalid, too many characters).

One interesting thing I discovered while reviewing the 1620 books: raising a number to a power in FORTRAN (**) was called "involution." I've never heard that term before.

Cheetah, maybe?

[Don Shepherd]

(04-04-2019 05:02 AM)toml_12953 Wrote:  Cheetah, maybe?

yeah, that sounds right! I forgot that old boys name!