Assembly Language

xor   flags, 01000000b           ; Reverse bit

; Similar instructions will work whenever the second operand of mod is a power of 2
and   eax, 0000001fh            ; EAX Mod 32

; This will work
sub   al, 30h            ; ASCII to Integer (Common)
; But if you don't know whether the source is a ASCII or a numeric string, you can use the one below
and   al, 00001111b   ; ASCII to Integer (Better)