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How to set, clear, toggle and checking a single bit in C?

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YasminRadwan26

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2022-06-23

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How to set, clear, toggle and checking a single bit in C?

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YasminRadwan26

2022-06-23

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Answer:

Note: Here I assume that bit of register starts with 0th position, it means the 2nd position is actually 3rd bits.

D7

D6

D5

D4

D3

D2

D1

D0

Setting N-th Bit

Setting an N-th bit means that if the N-th bit is 0, then set it to 1 and if it is 1 then leave it unchanged. In C, bitwise OR operator (|) use to set a bit of integral data type. As we know that | (Bitwise OR operator) evaluates a new integral value in which each bit position is 1 only when operand’s (integer type) has a 1 in that position.

In simple words, you can say that “Bitwise OR ” of two bits is always one if any one of them is one.

That means,
| 0 = 0
| 0 = 1
| 1 = 1
| 1 = 1

Algorithm to set the bits:

Number | = (1UL << nth Position);

Clearing a Bit

Clearing a bit means that if N-th bit is 1, then clear it to 0 and if it is 0 then leave it unchanged. Bitwise AND operator (&) use to clear a bit of integral data type. “AND” of two bits is always zero if any one of them is zero.

That means,
& 0 = 0
& 0 = 0
& 1 = 0
& 1 = 1

Algorithm to clear the bit:

To clear the nth bit, first, you need to invert the string of bits then AND it with the number.

Number &= ~(1UL << nth Position);

Checking a Bit

To check the nth bit, shift the ‘1’ nth position toward the left and then “AND” it with the number.

An algorithm to check the bit

Bit = Number & (1UL << nth);

Toggling a Bit

Toggling a bit means that if the N-th bit is 1, then change it to 0 and if it is 0 then change it to 1. Bitwise XOR (^) operator use to toggle the bit of an integral data type. To toggle the nth bit shift the ‘1’ nth position toward the left and “XOR” it.

That means,
^ 0 = 0
^ 0 = 1
^ 1 = 1
^ 1 = 0

An algorithm to toggle the bits

Number ^= (1UL << nth Position);

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