Demo of CPU instruction "neg"

negtest.c

#include <stdio.h>
#include <conio.h>

short negtest(short a);

int main(int argc, char* argv[])
{
        short a = 0;
        printf("a = %d, result = %d\n", a, negtest(a));

        a = 1;
        printf("a = %d, result = %d\n", a, negtest(a));

        getch();
        return 0;
}
//---------------------------------------------------------------------------

short negtest(short a)
{
	short b = 0;
        __asm
        {
         mov ax, a
         neg ax
         sbb ax, ax
         mov b, ax
        }
        return b; // this is optional, caller can get the returned value via register "ax"
}