bitwise_flags

A bitwise flag system written in C, modelling the kind of status register you'd find in embedded and defence software.

Three flags are defined — READY, ARMED, FAULT — each mapped to a unique bit in a uint8_t status register. The program demonstrates setting a flag, checking it, and toggling it off.

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How the operations work

Each flag is a power of 2, occupying a unique bit position:

#define READY (1 << 0)   // 00000001
#define ARMED (1 << 1)   // 00000010
#define FAULT (1 << 2)   // 00000100

Function	Code	Effect
set_flag	status |= flag	Forces bit ON
clear_flag	status &= ~flag	Forces bit OFF
toggle_flag	status ^= flag	Flips bit
check_flag	!!(status & flag)	Returns 0 or 1

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Build and run

gcc -Wall -Wextra -Werror -std=c11 -pedantic -o bitwise_flags main.c
./bitwise_flags

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Why this matters in embedded and defence C

Real hardware registers work exactly this way. For example, a UART status register might look like:

Bit 0 — TX ready
Bit 1 — RX data available  
Bit 2 — Parity error
Bit 3 — Overflow

You read the register, mask off the bit you care about, and act on it. The patterns here — |=, &= ~, ^=, & flag — are used constantly in device drivers, interrupt handlers, and comms stacks.

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