Using bitwise AND (&) with a mask to test whether a specific bit is set in an integer: is this a valid and standard technique?

Introduction / Context:Testing individual bits is a foundational skill in systems programming, device drivers, embedded development, and competitive programming. The classic approach is to use the bitwise AND operator with a mask that has the target bit set to 1 and all other bits 0.

Given Data / Assumptions:

• x is an integer value.
• mask is an integer with a 1 in the bit position we want to test and 0 elsewhere (e.g., 1u << k).
• We want a boolean-like result indicating whether the bit is set.

Concept / Approach:The expression (x & mask) != 0 evaluates to true if and only if the corresponding bit in x is 1. This works because AND preserves a 1 only where both operands have a 1. It is completely independent of endianness, as endianness affects byte ordering in memory, not the logical interpretation of bit positions within an arithmetic expression.

Step-by-Step Solution:

Verification / Alternative check:For x = 10 (1010b) and k = 1, mask = 0010b; x & mask = 0010b != 0 → bit 1 is set. For k = 0, mask = 0001b; x & mask = 0000b → bit 0 is not set.

Why Other Options Are Wrong:

Common Pitfalls:Using signed shifts incorrectly; forgetting to use unsigned types when shifting to build masks.

Final Answer:Correct.