programming on a drum computer

[hlreed]

The memory of a drum computer is cyclic. (Actually all memories are cyclic, but the cycle is now so big no one cares.) On the drum, the sequence itself had to be defined by the programmer. That is, and instruction also carried the address of the next instruction. There were no address labels, every instruction was a statement and goto.
This was actually fun to do. Since the drum was moving, good programming was finding the next spot that did not waste a drum cycle.<p>Now you know how old I am.

[bodgy]

I take it the clock on one of these machines beats rather than ticks. Did you write the code using the algorhythm method?<p>
colin

[hlreed]

colin, these were before any computer science. The magnetic drum revolved under 20 read and write heads. The basic code was moves from one track to another (which you could do in one instruction). These were cheap machines ($150,000)
Bendix made one, and the IBM 650 was one of these.
The input was an IBM model D typewriter with solinoids on every key. It had a paper tape reader, punch and eventually got card io and magnetic tape drives.
I wrote a program on it to simulate the assembler of the IBM 704 that replaced it. It could not have been done the other way around. (The Bendix machine was actually more capable than the IBM.)
I was young then.

[dyarker]

And the amplifiers for the read heads and write heads were miniature vacuum tubes?<p>The first piece of equipment I was trained to fix used magnetic cores for logic. Ceramic toriods wraped with iron tape, four insulated windings. Enclosed in plastic about 1/2" square. Two together worked like a flip-flop, but called a ping-pong from the "one" pulse bouncing back and forth. Discrete transistor logic equipment was also in use (bigger than TO-5), DTL appearing. Passing the test on the core machine decided if you were worth training on the newwer stuff.<p>Am I older?

[bodgy]

So were Faraday and Eddison jolly chappies when you attended their lectures? :p <p>Colin

[hlreed]

Dale, The drum computers were before core mamory was developed. Sort of an inverse solution. Computers had no memory, but a magnetic drum did, so make the drum the computer. This was all miniature tube stuff. Two tubes to a set, makes a flip/flop.
This was a Bendix G15D. Pity the users of A,B,C.
Wonderful machine. Also, these machines were personal, one user at a time. While you had it it was yours.

[dyarker]

Aahh, circa Klienschmit and model 15 teletypes, and vibrators to step up the voltage for tube type car radios.<p> :p