clrb, cmpb, movb, filb - perform byte operations
clrb (loc, length)
cmpb (p1, p2, length)
movb (dest, source, length)
filb (s, c, n)
Clrb zeros length bytes, starting at the pointer loc.
Cmpb compares its arguments and returns an integer greater than,
equal to or less than 0 according to whether p1 is
lexicographically greater than, equal to or less than p2. Cmpb
compares at most length bytes, but unlike strcmp(3), does not
stop upon reaching a zero byte.
Movb copies length bytes from source to dest.
Filb sets n bytes starting at s to character c.
Cmpb uses native character comparison that may be signed or
unsigned depending on the C compiler on your system.