Summary - Advanced bitwise

Combine masking, shifting and hacks to write a permission system.

Bitwise operation summary

In this summary you'll combine masking, setting, shifting and packing into one program. The program places bits into a raw value, then extracts the components with shift and mask.

The structure: you add bits to raw with |= (using shift). Then you extract those bits back with >> and &. This simulates a real hardware register: you write flags to it, then parse them when reading. One integer carries both identity and state; this is the basis of memory savings in embedded systems.

Exercise Write the bitwise summary program

Declare unsigned int raw = 0;. Place five shifted left by one with raw |= (5 << 1);. Set the first bit with raw |= 1;. Print with printf("raw=%u\n", raw);. Extract the id with unsigned int id = (raw >> 1) & 0x0F;. Get the active bit with unsigned int active = raw & 1;. Print with printf("id=%u active=%u\n", id, active);.

Show example solution

#include <stdio.h>

int main(void) {
    unsigned int raw = 0;
    raw |= (5 << 1);
    raw |= 1;
    printf("raw=%u\n", raw);
    unsigned int id = (raw >> 1) & 0x0F;
    unsigned int active = raw & 1;
    printf("id=%u active=%u\n", id, active);
    return 0;
}

Summary

In this group you learned advanced bitwise operations. You saw masking, setting and clearing bits, shifting, bit hacks and pack/unpack. You combined them to write a program that carries identity and state in one integer.

Bitwise operations appear everywhere from embedded systems to network protocols. Packing multiple values in one integer saves memory and bandwidth. In the next groups, typedef for type abstraction and finally the intermediate final project await you. Bitwise skill is essential for low-level programming.

Test yourself

Which operation sets a bit?
- &=
- >>
- |=
- ^
Show answer

|= — |= sets the bit to 1 with bitwise OR.
Match the bitwise operations

|=

Set bit
&=

Clear bit
<<

Shift left
& 0x0F

Low four bits

Next lesson: typedef and struct

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