Bitmasking Techniques
1. Setting a Bit
In this technique, we set a particular bit to 1 without touching any of the other bits. For this, we use the bitwise OR ( | ) operator and the left shift (<<) operator.
Basically, we take the integer 1 and using the left shift operator, shift the binary representation of 1 (that is 1 only) to n places where (n+1) is the place of bit which we want to set. Then using the bitwise OR operator we turn the given number’s (n+1)th bit to 1.
Syntax
number | (1 << bit_position_to_set)
Example:
C
#include <stdio.h> int main() { int x = 13; printf("Ans: %d", 13 | (1 << 5)); return 0; } |
Ans: 45
2. Clearing a Bit
In this operation, we set a specific bit to 0 (as opposed to 1 in the previous case) without touching any of the other bits. We use the bitwise AND operator (&), bitwise NOT operator (~), and the left shift operator (<<) to achieve the task.
Basically, we again take 1 and shift it the the specified position. Then, we perform the NOT operation on this to convert that into a 0 and other bits of the value (1<<n) to 1. Then we do the AND operation to clear the specified bit and obtain the result.
Syntax:
number & ~(1 << bit_position_to_clear)
Example:
C
#include<stdio.h> int main() { int x = 13; printf("Ans: %d", 13 & ~(1 << 2) ); return 0; } |
Ans: 9
3. Flipping a Bit
In this operation, we flip a specific bit that is if the bit is 0 then turn it to 1 else turn it to 0. This operation requires the use of bitwise XOR (^) operator along with the left shift (<<) operator.
Basically, as in previous operations, we shift 1 to the specified number of positions and then perform the XOR operation to flip the bit of the given number.
Syntax:
number ^ (1 << bit_position_to_flip)
Example:
C
#include<stdio.h> int main() { int x = 13; printf("Ans: %d", 13 ^ (1 << 3) ); return 0; } |
Ans: 5
4. Checking a Bit
In this operation, we check if a particular bit is 1 or not using the bitwise AND operator (&) along with the left shift operator (<<).
We shift 1 using the left shift operator to the specified position and then perform the bitwise AND operation on that so as to check if that specific bit is 0 or 1. If the bit is 0 then the result would be 0 else the result would be 2^(bit_position).
Syntax:
number & (1 << bit_position_to_check)
Example:
C
#include<stdio.h> int main() { printf("Ans: %d \n", 13 & (1 << 3) ); printf("Ans: %d \n", 13 & (1 << 4) ); return 0; } |
Ans: 8 Ans: 0
Bitmasking In C
In this article, we are going to learn about Bitmask in C which is a powerful way to basically work with bits and functions upon boolean logic. It can be used to store data compactly and with much more efficiency in certain cases.
What is a Bit?
A bit is the smallest unit of data which can either store a 0 or 1 inside it. All the data in the computer is stored using these bits. These 2 possible values can also be represented as boolean values that are True or False. Using this we can apply boolean logic to manipulate data stored on the computer.