Set Clear Toggle a Specific Bit in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

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What does it mean to set a specific bit in a number?

Setting a bit means changing that bit to 1, regardless of its current value.

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How do you clear a specific bit in a number?

Clearing a bit means changing that bit to 0, regardless of its current value.

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What does toggle a bit mean?

Toggling a bit means changing it from 0 to 1 or from 1 to 0.

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Which operator is used to set a bit at position pos in Python?

Use the bitwise OR operator (|) with (1 << pos). Example: num | (1 << pos)

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How do you clear a bit at position pos using bitwise operators?

Use bitwise AND (&) with the negation of (1 << pos): num & ~(1 << pos)

What is the result of setting bit 2 (0-based) in the number 8 (binary 1000)?

A 12 (binary 1100)

B 10 (binary 1010)

C 14 (binary 1110)

D 8 (binary 1000)

Setting bit 2 means turning the third bit from right to 1. 8 is 1000, setting bit 2 adds 4 (0100), so 1000 | 0100 = 1100 (12).

Which operation toggles a bit at position pos?

A num | (1 << pos)

B num & ~(1 << pos)

C num << pos

D num ^ (1 << pos)

XOR (^) with (1 << pos) flips the bit at pos: 0 becomes 1, 1 becomes 0.

Clearing a bit means:

A Flipping its value

B Setting it to 1

C Setting it to 0

D Leaving it unchanged

Clearing a bit means making that bit 0.

What does the expression num & ~(1 << pos) do?

A Sets bit pos to 1

B Clears bit pos to 0

C Toggles bit pos

D Checks if bit pos is set

It clears the bit at position pos by ANDing with the inverse mask.

If num = 5 (binary 0101), what is the result of toggling bit 0?

A 4 (binary 0100)

B 7 (binary 0111)

C 1 (binary 0001)

D 5 (binary 0101)

Toggling bit 0 flips the rightmost bit: 0101 ^ 0001 = 0100 (4).

Explain how to set, clear, and toggle a specific bit in a number using bitwise operators.

Think about how each operator affects bits at a given position.

Describe a real-life example where setting, clearing, or toggling bits might be useful.

Think about simple yes/no settings stored in one number.