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Fred2718 t1_j6izhk0 wrote

Reply to comment by d4rkh0rs in ELI5: What exactly is Random Access Memory? by FilmFrench

Disagree. The tapes I used, in the 70s and early 80s, 9 track 6250 BPI in NRZI, used 4K up to 32 K byte records with inter-record gaps. Controllers could count records on the fly without moving data to ram, until you got to the record you wanted.

A lot like sectoring on HDD.

/Pedant_Mode_Off

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d4rkh0rs t1_j6jk32l wrote

I just missed the tape era(unless Sinclair and Commodore count).
My understanding was the original systems had to read each header without a good index allowing them to jump to record X.
It sounds like your systems were a bit more advanced.

I bow to your greater experiance while wishing we could hear from the 50s and 60s.

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Fred2718 t1_j6jpki5 wrote

Mainframe systems maintained tape record indices ( after reading them from tape) in RAM or "drum" disk for just this reason. Read Knuth on efficient tape database searches, if you have a kink for antique software engineering. But bear in mind I was working on IBM 360 and 370 mainframes, followed by Data General minicomputers in the 80s.

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