Question

How to check if most significant bit (MSB) of a number is set or not in C

Answer 1

#include <stdio.h>

#define BITS sizeof(int) * 8 

int main()
{
    int n = 15, msb;

    msb = 1 << (BITS - 1);

    if (n & msb)
        printf("MSB set (1)\n");
    else
        printf("MSB not set (0)\n");
        
    msb = 1 << (4 - 1);  
    if (n & msb)
        printf("MSB set (1)\n");
    else
        printf("MSB not set (0)\n");
    
    n = -3;   
    msb = 1 << (BITS - 1);  
    if (n & msb)
        printf("MSB set (1)\n");
    else
        printf("MSB not set (0)\n");

    return 0;
}



/*
run:

MSB not set (0)
MSB set (1)
MSB set (1)

*/

 

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