Prior to ASCII existing, we already had at least four number systems, namely


So what were the needs that lead to the implementation of ASCII codes? Why was this code chosen, from a computer architecture perspective? I have searched online, but I haven't found a satisfactory answer.

  • $\begingroup$ I edited to clarify your question. Welcome to the site! $\endgroup$ Apr 20, 2020 at 16:17
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    $\begingroup$ Might be more appropriate for Retrocomputing. $\endgroup$ Apr 20, 2020 at 17:36
  • $\begingroup$ "ASCII codes" is the wrong terminology. ASCII is not a set of codes, it is an encoding. ASCII is not a number system either, it is an assignment of byte values to characters. $\endgroup$ Apr 21, 2020 at 9:07

2 Answers 2


Those r "number" systems they represent just numerical values. ASCII is a standard "coding" that include characters

(encode them as digital binary number, for example "A" is represented as 65)

Think of it as a fn that maps each number/character/symbol(enter for ex. has a code that I don't remember now) to a code number that will be represented to the computer in binary format


There were several different coding systems for characters around. The best known (alive up to this day) was IBM's EBCDIC, but most any manufacturer had their own. We had a DEC 2020, which handled several different character coding systems with it's 36-bit (!) words, a 6-bit DEC own, at least one 7-bit one (I think it was ASCII, with no parity bit) and 8-bit ones. If I remember right, it handled EBCDIC too, for IBM compatibility. All in the interest of scrimping a few bits per character (memory was precious in the '70es!).

Defining a character code of some sort was clearly a requirement if you wanted to read/write anything that wasn't just numbers, and that means agreeing on some mapping of (a subset of) the characters in use to numbers (the natural language inside the computer). You can get away with e.g. 6 bits (64 possible characters) if you restrict yourself a lot, ASCII's 7 bits (128 possibilities) is very cramped (specially if you want to write some non-English text, or even such English words as rôle, naïve, fiancé or others borrowed from other languages).

Even the prehistoric Morse code is a coding system for characters, just not in numbers. See also character encoding for it's history.


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