Why are 8 and 256 such important numbers in computer sciences?

Question

I don\'t know very well about RAM and HDD architecture, or how electronics deals with chunks of memory, but this always triggered my curiosity: Why did we choose to stop at 8 bi

Answer 1

Charles Petzold wrote an interesting book called Code that covers exactly this question. See chapter 15, Bytes and Hex.

Quotes from that chapter:

Eight bit values are inputs to the adders, latches and data selectors, and also outputs from these units. Eight-bit values are also defined by switches and displayed by lightbulbs, The data path in these circuits is thus said to be 8 bits wide. But why 8 bits? Why not 6 or 7 or 9 or 10?

... there's really no reason why it had to be built that way. Eight bits just seemed at the time to be a convenient amount, a nice biteful of bits, if you will.

...For a while, a byte meant simply the number of bits in a particular data path. But by the mid-1960s. in connection with the development of IBM's System/360 (their large complex of business computers), the word came to mean a group of 8 bits.

... One reason IBM gravitated toward 8-bit bytes was the ease in storing numbers in a format known as BCD. But as we'll see in the chapters ahead, quite by coincidence a byte is ideal for storing text because most written languages around the world (with the exception of the ideographs used in Chinese, Japanese and Korean) can be represented with fewer than 256 characters.