In fact, original version of ASCII even left some of the codes under 128 undefined or available for local redefinitions. This is why Smalltalk uses _ for assignment (it was left arrow on Alto) and why some still used encodings have local currency symbol (eg. ¥) in place of \.
Along with leaving codes 96–123 undefined, and significant differences in control codes, 1963 ASCII had ← and ↑ in the positions used for _ and ^ in 1967.
ISTR that a previous version of ASCII standardized the back-arrow in the underscore space. The same with up-arrow in place of caret, which is why the caret is used as an exponentiation operator in e.g., BASIC.
