NEG
Usage: NEG dest Modifies flags: AF CF OF PF SF ZF
Subtracts the 'dest' from 0 and saves the two's complement of 'dest' back into 'dest'.
Two's and One's Complement
NEG r/m8 ; F6 /3 [8086]
NEG r/m16 ; o16 F7 /3 [8086]
NEG r/m32 ; o32 F7 /3 [386]
NOT r/m8 ; F6 /2 [8086]
NOT r/m16 ; o16 F7 /2 [8086]
NOT r/m32 ; o32 F7 /2 [386]
NEG replaces the contents of its operand by the two's complement negation (invert all the bits and then add one) of the original value.
NOT, similarly, performs the one's complement (inverts all the bits, but does not add one).
Example:
mov eax 5
neg eax ; eax = FFFF FFFB > -5