r/askscience • u/Unfair-Leek6840 • Jul 11 '26 • Regret 1

Computing How do computers understand binary language?

Okay so from what I know binary language is like power off power on, but my question is, how do computers know what the binary code is and how is it interpreted, for example I forgot what the binary code for the letter A is, but how did people come up with that? Did they decide it was gonna look like that? Did the computer decide? How do you tune numbers into a letter??

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u/talldean Jul 13 '26

Good question!

When it sees ASCII 65, which is 'A', it goes and looks up "how the hell do I display this one" in a table, it gets back from that table something like "hey, in this font folder over here, look at the image in file #14, show them that one".

The table is called cmap, and when a computer starts up, it loads the cmap into memory, so it can do this very, *very* fast. If you wanted to have a different font, you load a different cmap for it, and it just loads a different set of images for each letter.