Bit shifting
- C course
- Intermediate
- Lesson 102/116
- 5 min
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.
Practice 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.
Starter code
#include <stdio.h>
// Define x as 1
// Shift left and print
// Define y as 256
// Shift right and print
int main(void) {
return 0;
}Sample 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;
}Expected output
16 64
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Complete the left shift expression
printf("%u
", x << ____);printf("%u
", x << 4);Explanation: x << 4 is equivalent to multiplying by sixteen.
2 Match the shift operations
| Term | Meaning |
|---|---|
<< |
Shift left |
>> |
Shift right |
1 << 4 |
Sixteen |
256 >> 2 |
Sixty four |
3 What is 1 << 4?
- 4
- 16 Correct answer
- 8
- 32
Explanation: Shifting 1 four places left gives 16 (2⁴).