The question is still a bit unclear.
A byte is 8 bits, and can therefore have any value between 0 and 255 decimal (2^8-1)
In a text file, the byte values are assigned to characters. Here is a link to a table: http://www.lookuptables.com/
Note that some ascii values are control characters--ie they trigger some action on a terminal--as opposed to causing text to be printed.