USING LOOPS

INTRODUCTION

• Looping, also called iteration, is a crucial feature in programming.

• It allows you to repeat a set of statements until specific conditions are met.

• In C, there are three primary loop constructs:

  • The while statement

  • The do-while statement

  • The for statement

THE WHILE LOOP

• The while loop repeatedly executes a statement while a given condition is true.

• When the condition is no longer true, the loop terminates.

• General form of the while statement:

while (expression) {
  statement;
}

Example Using the While Loop:

int x = 1;

while (x <= 5) {
    printf("%d ", x);
    x++;
}

THE DO-WHILE LOOP

• The do-while loop ensures that the statements in the loop are executed at least once before testing the condition.

General form of the do-while statement:

do {
  statement;0
} while (expression);

Example Using the Do-While Loop:

int y = 1;
do {
    printf("%d ", y);
    y++;
} while (y <= 5);

THE FOR LOOP

• The for loop provides a more concise way to control loops and combines initialization, condition, and increment in one line.

• General form of the for statement:

  for (expression1; expression2; expression3) {
    statement;
  }

  Example Using the For Loop:

  for (int i = 1; i <= 5; i++) {
      printf("%d ", i);
  }

THE NULL STATEMENT

• The for statement does not end with a semicolon; it contains either a statement block or a single statement.

• A for statement can have a null statement represented by a semicolon.

Example Using the Null Statement:

for (int i = 1; i <= 5; i++)
    ;  // This is a null statement

USING COMPLEX EXPRESSIONS IN A FOR STATEMENT

• You can use the comma operator to combine multiple expressions in the three parts of a for statement.

Example Using Complex Expressions in a For Loop:

for (int i = 1, j = 10; i != j; i++, j--) {
    /* statement block */
}

USING NESTED LOOPS

• Nested loops involve putting one loop inside another, creating inner and outer loops.

• When the program reaches an inner loop, it runs like any other statement inside the outer loop.

Example Using Nested Loops:

for (int i = 1; i <= 3; i++) {
    for (int j = 1; j <= 3; j++) {
        printf("%d %d ", i, j);
    }
    printf("\n");
}

SUMMARY

• Looping in C is a powerful feature that allows you to repeat code until specific conditions are met.

• The three loop statements, while, do-while, and for, offer different ways to implement loops.

• Pay attention to semicolon placement in for statements to avoid unintended consequences.

• You can use complex expressions in a for loop by using the comma operator.

• Nested loops are used when you need to create a loop within a loop, and inner loops complete before outer loops.