A quick primer on bit-wise and bit-shift operators

Bit-wise operators (|, &, ^, ~, |=, &=, ^=, ~=) and bit-shift operators (<<, >>, <<=, >>=) only work on limited types; which are int and char (and variations of int):

AND ‘&’

xi	yi	xi & yi
0	0	0
0	1	0
1	0	0
1	1	1

OR ‘|’

xi	yi	xi | yi
0	0	0
0	1	1
1	0	1
1	1	1

XOR ‘^’

xi	yi	xi ^ yi
0	0	0
0	1	1
1	0	1
1	1	0

NOT ‘~’

xi	~xi
0	1
1	0

LEFT-SHIFT ‘<<’

Suppose x is a 8-bit unsigned with following bit-values:

b7	b6	b5	b4	b3	b2	b1	b0
1	1	0	0	0	1	1	1

Then x<< 3 will be (shift the bits toward left by 3 bit):

b7	b6	b5	b4	b3	b2	b1	b0
0	0	1	1	1	0	0	0

When there is no overflow (no fall off the bit on left edge), shifting ‘n’ bits of number ‘x’ towards left is equivalent to multiplying the x by 2ⁿ.

RIGHT-SHIFT ‘>>’

Suppose x is a 8-bit unsigned with following bit-values:

b7	b6	b5	b4	b3	b2	b1	b0
1	1	0	0	0	1	1	1

Then x>> 3 will be (shift the bits toward right by 3 bit):

b7	b6	b5	b4	b3	b2	b1	b0
0	0	0	1	1	0	0	0

Shifting ‘n’ bits of number ‘x’ towards right is equivalent to dividing the x by 2ⁿ.

Have fun with following piece of code:

 

#include <stdio.h> int main() {             // SWAP the values             int x= 12, y= 66;             printf("Before SWAP: x = %d, y = %d\n", x, y);             x^=y;             y^=x;             x^=y;             printf("AFTER SWAP: x = %d, y = %d\n", x, y);             // LEFT-SHIFT operator             x = 3;             y = 2;             printf("\nBefore LEFT-SHIFT: x = %d, y = %d\n", x, y);             x << y ;             printf("After LEFT-SHIFT(\?\?): x = %d, y = %d\n", x, y);             printf("\nBefore LEFT-SHIFT: x = %d, y = %d\n", x, y);             x <<= y ; // x = x << y             printf("After LEFT-SHIFT(Observe x * 2*2): x = %d, y = %d\n", x, y); #define FIRST_BIT 0x1 #define SECOND_BIT 0x2 #define THIRD_BIT 0x4 #define FOURTH_BIT 0x8 #define GET_BIT(X,WHICH_BIT) (WHICH_BIT & X? true: false)             x = 10;             printf("\nBit values of x (=%d) is %d %d %d %d\n", x,                                     GET_BIT(x, FOURTH_BIT),                                     GET_BIT(x, THIRD_BIT),                                     GET_BIT(x, SECOND_BIT),                                     GET_BIT(x, FIRST_BIT));             return 0; }