RosettaCodeData/Task/Twos-complement/FreeBASIC/twos-complement-2.basic

Dim As Integer a = &b000011
Dim As Integer a2c, l
#ifdef __FB_64BIT__
    l = 16
    Asm
        mov rax, [a]
        neg rax
        mov [a2c], rax
    End Asm
#else
    l = 8
    Asm
        mov eax, [a]
        neg eax
        mov [a2c], eax
    End Asm
#endif

Print Bin(a, l); " -> "; Bin(a2c, l)
Sleep