Question

How to use bitwise AND "&" in C

Answer 1

#include <stdio.h>

char *toBinFormat(int n);

int main(int argc, char **argv) 
{ 
    // bit level AND (&). 
    // result is 0 if one bits is 1 and other bit is zero.
    // result is 0 when both bits are zero.  
    // result is 1 when both bits are 1
    
    char tmp;
    
    tmp = 7 & 1; 
    printf("%3d = %s\n", 7, toBinFormat(7));
    printf("%3d = %s\n", 1, toBinFormat(1));
    printf("tmp = 7 & 1 = %3d = %s\n\n", tmp, toBinFormat(tmp));
    
    tmp = 7 & 3;
    printf("%3d = %s\n", 7, toBinFormat(7));
    printf("%3d = %s\n", 3, toBinFormat(3));
    printf("tmp = 7 & 3 = %3d = %s\n\n", tmp, toBinFormat(tmp));
    
    tmp = 7 & 7;
    printf("%3d = %s\n", 7, toBinFormat(7));
    printf("%3d = %s\n", 7, toBinFormat(7));
    printf("tmp = 7 & 7 = %3d = %s\n\n", tmp, toBinFormat(tmp));
   
    tmp = 7 & 32; 
    printf("%3d = %s\n", 7, toBinFormat(7));
    printf("%3d = %s\n", 32, toBinFormat(32));
    printf("tmp = 7 & 32 = %3d = %s\n\n", tmp, toBinFormat(tmp));
    
    tmp = 7 & 8; 
    printf("%3d = %s\n", 7, toBinFormat(7));
    printf("%3d = %s\n", 8, toBinFormat(8));
    printf("tmp = 7 & 8 = %3d = %s\n\n", tmp, toBinFormat(tmp));
   
    return(0);
}

char *toBinFormat(int n)
{
    static char binary_value[9]; // without static binary_value is a local 
                                 // array that disappear after return
    int i;
    
    for(i = 0; i < 8; i++)
    {
        binary_value[i] = n & 0x80 ? '1' : '0';
        n <<= 1;
    }
    binary_value[i] = '\0';

    return binary_value;
}

/*
run:

  7 = 00000111
  1 = 00000001
tmp = 7 & 1 =   1 = 00000001

  7 = 00000111
  3 = 00000011
tmp = 7 & 3 =   3 = 00000011

  7 = 00000111
  7 = 00000111
tmp = 7 & 7 =   7 = 00000111

  7 = 00000111
 32 = 00100000
tmp = 7 & 32 =   0 = 00000000

  7 = 00000111
  8 = 00001000
tmp = 7 & 8 =   0 = 00000000

*/

 

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