Bitmasks and Bit Manipulation

1#include <stdio.h>
2
3// Helper function to print binary
4void printBinary(unsigned int n, int bits) {
5    for (int i = bits - 1; i >= 0; i--) {
6        printf("%d", (n >> i) & 1);
7    }
8}
9
10int main() {
11    unsigned int x = 0b00001010;  // Start with 10
12    
13    printf("Original:    ");
14    printBinary(x, 8);
15    printf(" = %d\n", x);
16    
17    // SET bit 0 (rightmost)
18    x = x | (1 << 0);
19    printf("Set bit 0:   ");
20    printBinary(x, 8);
21    printf(" = %d\n", x);
22    
23    // SET bit 4
24    x = x | (1 << 4);
25    printf("Set bit 4:   ");
26    printBinary(x, 8);
27    printf(" = %d\n", x);
28    
29    // CLEAR bit 1
30    x = x & ~(1 << 1);
31    printf("Clear bit 1: ");
32    printBinary(x, 8);
33    printf(" = %d\n", x);
34    
35    // TOGGLE bit 3
36    x = x ^ (1 << 3);
37    printf("Toggle bit 3:");
38    printBinary(x, 8);
39    printf(" = %d\n", x);
40    
41    // CHECK if bit 4 is set
42    if ((x >> 4) & 1) {
43        printf("Bit 4 is SET\n");
44    } else {
45        printf("Bit 4 is NOT set\n");
46    }
47    
48    return 0;
49}

1#include <stdio.h>
2
3// Define permission flags using bit positions
4#define READ    (1 << 0)  // 001 = 1
5#define WRITE   (1 << 1)  // 010 = 2
6#define EXECUTE (1 << 2)  // 100 = 4
7
8void printPermissions(int perms) {
9    printf("Permissions: ");
10    if (perms & READ)    printf("Read ");
11    if (perms & WRITE)   printf("Write ");
12    if (perms & EXECUTE) printf("Execute ");
13    printf("\n");
14}
15
16int main() {
17    int permissions = 0;  // No permissions
18    
19    printf("=== File Permission System ===\n\n");
20    
21    // Grant READ permission
22    permissions |= READ;
23    printf("After granting READ:\n");
24    printPermissions(permissions);
25    
26    // Grant WRITE permission
27    permissions |= WRITE;
28    printf("After granting WRITE:\n");
29    printPermissions(permissions);
30    
31    // Grant EXECUTE permission
32    permissions |= EXECUTE;
33    printf("After granting EXECUTE:\n");
34    printPermissions(permissions);
35    
36    // Revoke WRITE permission
37    permissions &= ~WRITE;
38    printf("After revoking WRITE:\n");
39    printPermissions(permissions);
40    
41    // Check specific permission
42    if (permissions & EXECUTE) {
43        printf("\nUser CAN execute this file.\n");
44    }
45    
46    if (!(permissions & WRITE)) {
47        printf("User CANNOT write to this file.\n");
48    }
49    
50    // Grant multiple at once
51    int fullAccess = READ | WRITE | EXECUTE;
52    printf("\nFull access value: %d (binary: ", fullAccess);
53    for (int i = 2; i >= 0; i--) printf("%d", (fullAccess >> i) & 1);
54    printf(")\n");
55    
56    return 0;
57}

1#include <stdio.h>
2
3// Game state flags
4#define HAS_SWORD      (1 << 0)  // 0001
5#define HAS_SHIELD     (1 << 1)  // 0010
6#define HAS_POTION     (1 << 2)  // 0100
7#define QUEST_COMPLETE (1 << 3)  // 1000
8
9void printInventory(int flags) {
10    printf("Inventory: ");
11    if (flags & HAS_SWORD)      printf("[Sword] ");
12    if (flags & HAS_SHIELD)     printf("[Shield] ");
13    if (flags & HAS_POTION)     printf("[Potion] ");
14    if (flags & QUEST_COMPLETE) printf("[Quest✓] ");
15    if (flags == 0)             printf("[Empty]");
16    printf("\n");
17}
18
19int main() {
20    int playerFlags = 0;
21    
22    printf("=== Adventure Game ===\n\n");
23    printInventory(playerFlags);
24    
25    // Pick up sword
26    printf("You found a SWORD!\n");
27    playerFlags |= HAS_SWORD;
28    printInventory(playerFlags);
29    
30    // Pick up shield
31    printf("You found a SHIELD!\n");
32    playerFlags |= HAS_SHIELD;
33    printInventory(playerFlags);
34    
35    // Use potion (can't - don't have one!)
36    if (playerFlags & HAS_POTION) {
37        printf("Used potion!\n");
38        playerFlags &= ~HAS_POTION;
39    } else {
40        printf("No potion to use!\n");
41    }
42    
43    // Pick up potion
44    printf("You found a POTION!\n");
45    playerFlags |= HAS_POTION;
46    printInventory(playerFlags);
47    
48    // Complete quest
49    printf("QUEST COMPLETE!\n");
50    playerFlags |= QUEST_COMPLETE;
51    printInventory(playerFlags);
52    
53    // Check if ready for boss (need sword AND shield)
54    if ((playerFlags & HAS_SWORD) && (playerFlags & HAS_SHIELD)) {
55        printf("\nYou are ready to fight the boss!\n");
56    }
57    
58    return 0;
59}