Q:

Why ASCII only have 1/4, 1/2 & 3/4?

How about 1/3, or 1/5 or something else?
Is 1/4, 1/2 & 3/4 enough?
Thank you.

A:

ASCII is 7 bits. That's 128 Characters, including the non printable ones. 
Consider 10 for numerals, 52 for upper and lower case, some punctuations and around 30 control character you are not left with much.
With such a small number of characters, they needed to reserve them for the more used ones.

