Bit manipulation techniques - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the bitwise AND operator (&) do in C?

It compares each bit of two numbers and returns 1 only if both bits are 1; otherwise, it returns 0.

beginner

How do you set (turn on) the nth bit of a number using bit manipulation?

Use the OR operator (|) with a mask that has only the nth bit set: <br> number |= (1 << n);

intermediate

What is the purpose of the bitwise XOR operator (^) in bit manipulation?

It returns 1 for bits that are different and 0 for bits that are the same. It can be used to toggle bits.

beginner

How can you check if the nth bit of a number is set (1)?

Use the AND operator with a mask and check if the result is not zero: <br> if (number & (1 << n)) { /* nth bit is set */ }

beginner

What does the left shift operator (<<) do in bit manipulation?

It shifts all bits in a number to the left by a specified number of positions, adding zeros on the right. This multiplies the number by 2 for each shift.

Which operator is used to clear (turn off) the nth bit of a number in C?

A AND (&) with the complement of (1 << n)

B OR (|) with (1 << n)

C XOR (^) with (1 << n)

D Left shift (<<) by n

To clear the nth bit, use AND with the mask that has all bits set except the nth bit: number &= ~(1 << n);

What is the result of 5 & 3 in binary?

A 7

B 6

C 1

D 0

5 in binary is 0101, 3 is 0011; AND gives 0001 which is 1.

How do you toggle the 2nd bit of a number?

A number ^= (1 << 2);

B number &= ~(1 << 2);

C number |= (1 << 2);

D number << 2;

XOR (^) with (1 << 2) flips the 2nd bit.

What does the expression (number >> 1) do?

A Sets the 1st bit of number

B Shifts bits of number to the right by 1, dividing by 2

C Shifts bits of number to the left by 1, multiplying by 2

D Clears the 1st bit of number

Right shift by 1 moves bits right, effectively dividing by 2.

Which operator can be used to check if a number is even or odd?

A Left shift (<<) by 1

B OR (|) with 1

C XOR (^) with 1

D AND (&) with 1

Checking number & 1 returns 0 if even, 1 if odd.

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

Think about how masks with a single bit set can change bits using AND, OR, XOR.

Describe how left shift and right shift operators affect a number's value and bits.

Consider how shifting bits changes the number in binary.