What is byte addressability?

Answer 1

Early computers were placed in 2 categories, allowing them to be optimized to their user's needs:

• scientific - these computers had large fixed wordsizes(e.g. 24 bits, 36 bits, 40 bits, 48 bits, 60 bits) and their memory could generally only be addressed to the word, no smaller sized entity could be addressed.
• business - these computers addressed memory by characters (e.g. 6 bits), if they supported the concept of words at all the machine usually had a variable wordlength that the programmer could specify in someway according to the needs of the program. Their memory was addressed to the character.

This was true for both first and second generation computers, but in the third generation computer manufacturers decided to unify the 2 categories of computers to reduce the number of different architectures they had to support. IBM with the introduction of the System/360 in 1964 introduced the concept of thebyte (8 bits) as an independently addressable part of a large fixed word (32 bits). Other computer manufacturers soon followed this practice too.