Bit operations

Last reviewed May 28, 2026 Content v20260528

Track mode: server_compiled
Means: Compiled runner
Reading: ~1 min
Level: advanced

This lesson

This lesson teaches Bit operations: the syntax, patterns, and safety habits you need before advancing in C.

Teams still ship Bit operations in C codebases—skipping it leaves gaps in debugging and code reviews.

You will apply Bit operations in contexts like: Hardware registers, protocol packing, and checksum implementations.

Write C in main.c with int main(), click Run on server—the dev runner compiles with cc/gcc -std=c11 and runs the binary; read stderr for compile and linker errors (LEARNING_RUNNER_ENABLED=true).

When pointers, structs, and basic control flow from intermediate lessons are familiar.

Bitwise operators manipulate individual bits—essential for flags, embedded registers, codecs, and low-level protocols.

Operators

& — AND
| — OR
^ — XOR
<<, >> — shifts
~ — NOT

Mask example

#define FLAG_READY (1u << 0)
unsigned flags = FLAG_READY;
if (flags & FLAG_READY) { /* set */ }

Use unsigned types for portable shift behavior. Shifting past width is UB.

Important interview questions and answers

Q: Set bit n?
A: x |= (1u << n)
Q: Clear bit n?
A: x &= ~(1u << n)
Q: Logical vs arithmetic shift?
A: Right shift of signed negative values is implementation-defined in C—prefer unsigned for portable bit tricks.

Self-check

What is 5 & 3?
How do you test if bit 2 is set?

Interview prep

Set bit n?: flags |= (1u << n); — use unsigned types for portable shift behavior.

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Self-reflection (saved on this device)

Not saved yet.

Playground

Runs on the configured server runner (dev: npm run runner with LEARNING_RUNNER_ENABLED=true). Output appears below the editor.

Code runner not available

Server runner is disabled. Set LEARNING_RUNNER_ENABLED=true and LEARNING_RUNNER_URL in .env (see .env.example).

Check yourself

Multiple choice — immediate feedback.

Discussion

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Mask idiom?
Endianness?

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