In order to deal with data on paper tape or from communications equipment, a system of shifts could be used to represent the full 128 characters of ASCII. Character #74 (i.e. octal 74) was considered an alpha shift and indicated subsequent characters were to be considered uppercase, #75 was a beta shift and indicated subsequent characters were in lower case, and #76 the delta shift, indicating the next character was a control character. Thus the ASCII string "Hello World" would be encoded as "αHβELLO αWβORLD". Character #77 was a fill (ignore) character, similar to the rubout character in the 7-bit world.
