Bit shifting

Learn bit shifting patterns with << and >>.

Bit shifting

Bit shifting moves a value's bits left (<<) or right (>>). Left shift moves every bit one position up; it is equivalent to multiplying by a power of two.

Example: 1 << 4 gives 16; shifting 1 four places left yields sixteen. Similarly 256 >> 2 gives 64; shifting right two places is equivalent to dividing by four. For unsigned types, right shift always fills with zeros; for signed types the sign bit may be preserved. Shifting is a core tool for separating color channels and bit packing.

Shifts and powers of two

Shifting is the fast way to multiply and divide by powers of two. n << k means n * 2^k; n >> k means n / 2^k (integer division).

Example: 1 << 4 = 16 (1 × 2⁴), 256 >> 2 = 64 (256 ÷ 4). CPUs do it faster than multiplication, so old code used it for performance. Modern compilers turn n * 4 into n << 2 automatically; so today multiplication is preferred for readability. But in bit packing, shifting is still essential; it is the only way to place bits at the right position.

Exercise Write a bit shifting program

Declare unsigned int x = 1;. Print with printf("%u\n", x << 4); to shift left. Declare unsigned int y = 256;. Print with printf("%u\n", y >> 2); to shift right.

Show example solution

#include <stdio.h>

int main(void) {
    unsigned int x = 1;
    printf("%u\n", x << 4);
    unsigned int y = 256;
    printf("%u\n", y >> 2);
    return 0;
}

Test yourself

Complete the left shift expression

printf("%u
", x << ____);

Show answer

printf("%u
", x << 4);

Match the shift operations

<<

Shift left
>>

Shift right
1 << 4

Sixteen
256 >> 2

Sixty four
What is 1 << 4?
- 4
- 16
- 8
- 32
Show answer

16 — Shifting 1 four places left gives 16 (2⁴).

Next lesson: Bit hacks

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