Loops in C

1#include <stdio.h>
2
3int main() {
4    // Demonstrating true/false values
5    printf("Testing loop conditions:\n\n");
6    
7    // while(0) - FALSE, never runs
8    printf("while(0): ");
9    while (0) {
10        printf("This never prints");
11    }
12    printf("Skipped (0 is FALSE)\n");
13    
14    // while(1) runs once with break
15    printf("while(1): ");
16    while (1) {
17        printf("Runs! (1 is TRUE)\n");
18        break;
19    }
20    
21    // Negative numbers are TRUE
22    int x = -5;
23    printf("while(-5): ");
24    while (x) {
25        printf("Runs! (-5 is TRUE, non-zero)\n");
26        break;
27    }
28    
29    // Comparison results
30    printf("\nComparison expressions:\n");
31    printf("5 > 3 evaluates to: %d (TRUE)\n", 5 > 3);
32    printf("5 < 3 evaluates to: %d (FALSE)\n", 5 < 3);
33    printf("5 == 5 evaluates to: %d (TRUE)\n", 5 == 5);
34    
35    return 0;
36}

1#include <stdio.h>
2
3int main() {
4    int num, sum = 0;
5    
6    printf("Enter numbers to sum (0 to stop):\n");
7    
8    printf("Enter number: ");
9    scanf("%d", &num);
10    
11    while (num != 0) {    // Continue until 0 is entered
12        sum += num;
13        printf("Running sum: %d\n", sum);
14        printf("Enter number: ");
15        scanf("%d", &num);
16    }
17    
18    printf("\nFinal sum: %d\n", sum);
19    
20    return 0;
21}

1#include <stdio.h>
2
3int main() {
4    // Pattern 1: Count up (0 to 4)
5    printf("Count up: ");
6    for (int i = 0; i < 5; i++) {
7        printf("%d ", i);
8    }
9    printf("\n");
10    
11    // Pattern 2: Count down (5 to 1)
12    printf("Count down: ");
13    for (int i = 5; i >= 1; i--) {
14        printf("%d ", i);
15    }
16    printf("\n");
17    
18    // Pattern 3: Skip values (even numbers)
19    printf("Even numbers: ");
20    for (int i = 0; i <= 10; i += 2) {
21        printf("%d ", i);
22    }
23    printf("\n");
24    
25    // Pattern 4: Multiple variables
26    printf("Two counters: ");
27    for (int i = 0, j = 10; i < j; i++, j--) {
28        printf("(%d,%d) ", i, j);
29    }
30    printf("\n");
31    
32    return 0;
33}

1#include <stdio.h>
2
3int main() {
4    printf("Multiplication Table (1-5):\n\n");
5    
6    // Print header row
7    printf("    ");
8    for (int j = 1; j <= 5; j++) {
9        printf("%4d", j);
10    }
11    printf("\n    --------------------\n");
12    
13    // Outer loop: rows (1 to 5)
14    for (int i = 1; i <= 5; i++) {
15        printf("%d | ", i);
16        
17        // Inner loop: columns (1 to 5)
18        for (int j = 1; j <= 5; j++) {
19            printf("%4d", i * j);
20        }
21        printf("\n");
22    }
23    
24    return 0;
25}

1#include <stdio.h>
2
3int main() {
4    int rows = 5;
5    
6    printf("Right Triangle Pattern:\n");
7    
8    for (int i = 1; i <= rows; i++) {
9        // Inner loop runs 'i' times each row
10        for (int j = 1; j <= i; j++) {
11            printf("* ");
12        }
13        printf("\n");
14    }
15    
16    return 0;
17}

1#include <stdio.h>
2
3int main() {
4    int age;
5    
6    // Input validation with do-while
7    do {
8        printf("Enter your age (1-120): ");
9        scanf("%d", &age);
10        
11        if (age < 1 || age > 120) {
12            printf("Invalid age! Please try again.\n");
13        }
14    } while (age < 1 || age > 120);
15    
16    printf("\nValid age entered: %d\n", age);
17    
18    if (age >= 18) {
19        printf("You are an adult.\n");
20    } else {
21        printf("You are a minor.\n");
22    }
23    
24    return 0;
25}

1#include <stdio.h>
2
3int main() {
4    // BREAK: Exit loop when target found
5    printf("Finding first multiple of 7 (1-20):\n");
6    for (int i = 1; i <= 20; i++) {
7        if (i % 7 == 0) {
8            printf("Found: %d\n", i);
9            break;  // Stop searching
10        }
11        printf("%d ", i);
12    }
13    
14    // CONTINUE: Skip certain values
15    printf("\nOdd numbers from 1-10:\n");
16    for (int i = 1; i <= 10; i++) {
17        if (i % 2 == 0) {
18            continue;  // Skip even numbers
19        }
20        printf("%d ", i);
21    }
22    printf("\n");
23    
24    return 0;
25}

1#include <stdio.h>
2
3int main() {
4    // Finding coordinates in a 2D search
5    printf("Searching for (2,2) in 4x4 grid:\n");
6    
7    for (int i = 0; i < 4; i++) {
8        for (int j = 0; j < 4; j++) {
9            printf("Checking (%d,%d)\n", i, j);
10            if (i == 2 && j == 2) {
11                printf(">>> FOUND! <<<\n");
12                goto found;  // Exit BOTH loops
13            }
14        }
15    }
16    printf("Not found.\n");
17    goto end;
18    
19    found:
20    printf("Search complete - target located.\n");
21    
22    end:
23    return 0;
24}

1#include <stdio.h>
2
3int main() {
4    int choice, a, b;
5    
6    while (1) {  // Infinite loop
7        printf("\n=== Calculator ===\n");
8        printf("1. Add\n");
9        printf("2. Subtract\n");
10        printf("3. Multiply\n");
11        printf("4. Exit\n");
12        printf("Choice: ");
13        scanf("%d", &choice);
14        
15        if (choice == 4) {
16            printf("Goodbye!\n");
17            break;  // Exit infinite loop
18        }
19        
20        if (choice < 1 || choice > 4) {
21            printf("Invalid choice!\n");
22            continue;  // Skip to next iteration
23        }
24        
25        printf("Enter two numbers: ");
26        scanf("%d %d", &a, &b);
27        
28        switch (choice) {
29            case 1: printf("Result: %d\n", a + b); break;
30            case 2: printf("Result: %d\n", a - b); break;
31            case 3: printf("Result: %d\n", a * b); break;
32        }
33    }
34    
35    return 0;
36}