Loop Control

2 min read

Loop control statements change the normal sequential execution of loops, giving the programmer precise control over when a loop terminates or skips an iteration.

1. The `break` Statement

The break statement is used to immediately terminate the innermost loop (or switch statement) it is contained within. Execution proceeds to the statement immediately following the loop body.

Use Case: Exiting a Loop Early

This is often used when a condition is met inside the loop that makes further iteration unnecessary (e.g., finding a target value).

int target = 5;
int i;

for (i = 1; i <= 10; i++) {
    printf("Checking %d...\n", i);
    if (i == target) {
        printf("Target found!\n");
        break; // Exit the loop entirely
    }
}
printf("Loop finished.\n");
// Output stops after checking 5.

2. The `continue` Statement

The continue statement skips the remaining code inside the current iteration of a loop and immediately proceeds to the next iteration.

Use Case: Skipping Code Blocks

This is often used to bypass specific iterations that meet a certain condition (e.g., skipping odd numbers or corrupted data).

int i;

for (i = 1; i <= 5; i++) {
    if (i % 2 != 0) { // Check if 'i' is odd
        continue;     // Skip the rest of the current iteration
    }
    printf("Even number: %d\n", i);
}
// Output: Even number: 2, Even number: 4

3. The `switch` Statement

The switch statement is a multi-way decision structure that is often more readable and efficient than a long if-else if-else chain, especially when testing a single variable against many discrete integer or character values.

Key Components

switch (expression): The integer or character expression whose value is tested.
case constant: Marks a block of code to execute if the expression matches the constant.
break: Essential! Prevents execution from “falling through” to the next case block.
default: Optional block executed if none of the case constants match the expression (similar to the final else).

Example

char grade = 'B';

switch (grade) {
    case 'A':
        printf("Excellent!\n");
        break;
    case 'B':
        printf("Good Job.\n"); // This code executes
        break;
    case 'C':
        printf("Passed.\n");
        break;
    default:
        printf("Needs improvement.\n");
}
// Output: Good Job.

Crucial Detail: If you forget the break statement in a case block, execution will “fall through” and execute the code in the subsequent case blocks until a break or the end of the switch is reached.