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I have been reading the book of Goldstine on computers and I was wondering how ENIAC could activate a computation using numbers (the antecedent of the stored program concept).

Goldstine wrote that instructions were coded as numbers with part of the number used to identify a register with a stored value to work upon and the other half to select the "operation is to be executed".

Now, how was the operation selected? Let's say the punched card had the number 4 punched to select an operation and let's say operation 4 was a multiplication. Multiplication was carried out by a dedicated "panel" that is, a set of circuits arranged inside a cupboard that could perform only multiplication.

Would the number 4 on the punched card carry an electrical signal to the accumulator number 4 and the number stored in this accumulator send a signal to the multiplication panel? Or did the number stored in accumulator 4 had a further meaning?

Goldstine wrote that a typical order encoded as an instruction would "transfer a number from a specific location in the memory [an accumulator?] into the arithmetic organ [a panel?]; add the content of a delay lines in the arithmetic organ [?]; transfer a number from the arithmetic organ into a specific memory location". Is there a simple visualization of this process?

Thank you

Gigiux
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    processors still use numbers to signify instructions – jsotola Sep 18 '20 at 07:26
  • Back then, *delay lines* were almost equivalent to today's memory. Delay lines might have been used inside the calculation unit too, to keep intermediate values of computations. They were slow, serial-access, and volatile - meaning that if you didn't refresh them constantly, data disappeared. – glen_geek Sep 18 '20 at 14:41
  • OK, so did ENIAC used the same fetch-decode-execute cycle of modern computers? were the delay lines the three registers? how did the master programmer know that a given number-instruction was associated with an operation such as adding? (and how the modern computer known it today, for that matter). Tx – Gigiux Sep 18 '20 at 16:53

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