Understanding the bitwise AND (&) operator in C#: which uses are correct? 1) Invert a bit 2) Put a bit ON (set to 1) 3) Put a bit OFF (clear to 0) 4) Check whether a bit is ON 5) Check whether a bit is OFF

Introduction / Context:
Bitwise AND (&) is frequently used with masks for clearing and testing bits. This question asks which operations are appropriate for &.

Given Data / Assumptions:

• We have integer/byte values and masks.
• We want to categorize valid uses of &.

Concept / Approach:
AND with a mask of 0 clears a bit; with 1, it preserves the bit. Therefore, & can clear bits and test bits. It cannot invert or set bits to 1; those operations are best done with XOR (^) for invert and OR (|) for setting.

Step-by-Step Solution:

Verification / Alternative check:
Example: n = 0b1011 (11), mask = 0b1000 (8). n & mask = 8 (bit ON). Clearing: n & ~mask = 0b0011.

Why Other Options Are Wrong:

• 1: Inversion requires XOR (^) with mask or bitwise NOT (~) on the whole value, not &.
• 2: Setting a bit ON uses OR (|) with the mask.

Common Pitfalls:
Using & when you actually want to set bits ON (use |) or invert (use ^ or ~ appropriately).

Final Answer:
3, 4, 5