#include <msp430.h>
signed long x=0x0005;
int y,i,n;
void main(void)
{
    y=~x;
    i=y+1;

}

#define MASK 0x80000000

// Return value of "0" means the bit wasn't set, "1" means the bit was.
//      You can check as many bits as you want with this call.
int ApplyMask(int number) {
    return number & MASK;
}

int CheckBit(int number, int bitIndex) {
    return number & (1 << bitIndex);
}

bool isSetBit (signed long number, int bit)
{
    assert ((bit >= 0) && (bit < (sizeof (signed long) * 8)));
    return (number & (((signed long) 1) << bit)) != 0;
}

if (isSetBit (y, sizeof (y) * 8 - 1))
    ...