C: العمليات على البتات

Decimal 42  =  Binary 00101010
Decimal 255 =  Binary 11111111

Decimal  5  =  00000101
Decimal -5  =  11111011  (two's complement)

  1010  (10)
& 1100  (12)
------
  1000  (8)

  1010  (10)
| 1100  (12)
------
  1110  (14)

  1010  (10)
^ 1100  (12)
------
  0110  (6)

~ 00101010  (42)
= 11010101  (-43, two's complement)

5 << 2
= 00000101 << 2
= 00010100
= 20

20 >> 2
= 00010100 >> 2
= 00000101
= 5

flags |= (1 << n);

flags &= ~(1 << n);

flags ^= (1 << n);

if (flags & (1 << n)) {
}

#include <stdio.h>

void print_bits(unsigned char val) {
    for (int i = 7; i >= 0; i--) {
        printf("%d", (val >> i) & 1);
    }
    printf("\n");
}

int main(void) {
    unsigned char flags = 0;

    flags |= (1 << 3);
    printf("Set bit 3: ");
    print_bits(flags);

    flags |= (1 << 5);
    printf("Set bit 5: ");
    print_bits(flags);

    flags &= ~(1 << 3);
    printf("Clear bit 3: ");
    print_bits(flags);

    flags ^= (1 << 5);
    printf("Toggle bit 5: ");
    print_bits(flags);

    flags ^= (1 << 7);
    printf("Toggle bit 7: ");
    print_bits(flags);

    if (flags & (1 << 7)) {
        printf("Bit 7 is 1\n");
    }

    return 0;
}

Set bit 3: 00001000
Set bit 5: 00101000
Clear bit 3: 00100000
Toggle bit 5: 00000000
Toggle bit 7: 10000000
Bit 7 is 1

unsigned int val = 0xABCD;
unsigned int low_byte = val & 0xFF;

unsigned int high_byte = (val >> 8) & 0xFF;

unsigned int combined = (high << 8) | low;

#include <stdio.h>

int main(void) {
    unsigned int color = 0xFF6633;

    unsigned char r = (color >> 16) & 0xFF;
    unsigned char g = (color >> 8) & 0xFF;
    unsigned char b = color & 0xFF;

    printf("Color #FF6633:\n");
    printf("  Red: %d\n", r);
    printf("  Green: %d\n", g);
    printf("  Blue: %d\n", b);

    unsigned int new_color = 0x00;
    new_color |= ((r / 2) << 16);
    new_color |= ((g / 2) << 8);
    new_color |= (b / 2);
    printf("Darkened: #%06X\n", new_color);

    return 0;
}

Color #FF6633:
  Red: 255
  Green: 102
  Blue: 51
Darkened: #7F3319

rwxr-xr-x = 111101101 = 0755
rw-r--r-- = 110100100 = 0644

#include <stdio.h>

#define READ    (1 << 2)
#define WRITE   (1 << 1)
#define EXECUTE (1 << 0)

void show_permission(unsigned char perm) {
    printf("%c", (perm & READ) ? 'r' : '-');
    printf("%c", (perm & WRITE) ? 'w' : '-');
    printf("%c", (perm & EXECUTE) ? 'x' : '-');
}

int main(void) {
    unsigned char owner  = READ | WRITE | EXECUTE;
    unsigned char group  = READ | EXECUTE;
    unsigned char other  = READ | EXECUTE;

    printf("Permissions: ");
    show_permission(owner);
    show_permission(group);
    show_permission(other);
    printf("\n");

    owner &= ~WRITE;
    printf("After removing write: ");
    show_permission(owner);
    show_permission(group);
    show_permission(other);
    printf("\n");

    return 0;
}

Permissions: rwxr-xr-x
After removing write: r-xr-xr-x

a ^= b;
b ^= a;
a ^= b;

if (n & 1) {
}

n << 1
n << 2
n >> 1

unsigned int pow2 = 1u << n;

unsigned int aligned = (value + mask) & ~mask;

#include <stdio.h>

int main(void) {
    int values[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    for (int i = 0; i < 10; i++) {
        int aligned = (values[i] + 3) & ~3;
        printf("%d -> %d\n", values[i], aligned);
    }
    return 0;
}

0 -> 0
1 -> 4
2 -> 4
3 -> 4
4 -> 4
5 -> 8
6 -> 8
7 -> 8
8 -> 8
9 -> 12