C++ While Loop & For Loop & Break/Continue | C++ Programming for Beginners - Class 10 PDF Download

C++ Loops

• Loops can execute a block of code as long as a specified condition is reached.
• Loops are handy because they save time, reduce errors, and they make code more readable.

C++ While Loop

The while loop loops through a block of code as long as a specified condition is true:

Syntax

while (condition) {

  // code block to be executed

}

In the example below, the code in the loop will run, over and over again, as long as a variable (i) is less than 5:

Example

int i = 0;

while (i < 5) {

  cout << i << "\n";

  i++;

}

Note: Do not forget to increase the variable used in the condition, otherwise the loop will never end!

The Do/While Loop

The do/while loop is a variant of the while loop. This loop will execute the code block once, before checking if the condition is true, then it will repeat the loop as long as the condition is true.

Syntax

do {

  // code block to be executed

}

while (condition);

The example below uses a do/while loop. The loop will always be executed at least once, even if the condition is false, because the code block is executed before the condition is tested:

Example

int i = 0;

do {

  cout << i << "\n";

  i++;

}

while (i < 5);

C++ For Loop

When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop:

Syntax

for (statement 1; statement 2; statement 3) {

  // code block to be executed

}

• Statement 1 is executed (one time) before the execution of the code block.
• Statement 2 defines the condition for executing the code block.
• Statement 3 is executed (every time) after the code block has been executed.

The example below will print the numbers 0 to 4:

Example

for (int i = 0; i < 5; i++) {

  cout << i << "\n";

}

Example explained

• Statement 1 sets a variable before the loop starts (int i = 0).
• Statement 2 defines the condition for the loop to run (i must be less than 5). If the condition is true, the loop will start over again, if it is false, the loop will end.
• Statement 3 increases a value (i++) each time the code block in the loop has been executed.

Another Example

This example will only print even values between 0 and 10:

Example

for (int i = 0; i <= 10; i = i + 2) {

  cout << i << "\n";

}

C++ Break

• You have already seen the break statement used in an earlier chapter of this tutorial. It was used to "jump out" of a switch statement.
• The break statement can also be used to jump out of a loop.
• This example jumps out of the loop when i is equal to 4:

Example

for (int i = 0; i < 10; i++) {

  if (i == 4) {

    break;

  }

  cout << i << "\n";

}

C++ Continue

The continue statement breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop.
This example skips the value of 4:

Example

for (int i = 0; i < 10; i++) {

  if (i == 4) {

    continue;

  }

  cout << i << "\n";

}

Break and Continue in While Loop

You can also use break and continue in while loops:

Break Example

int i = 0;

while (i < 10) {

  cout << i << "\n";

  i++;

  if (i == 4) {

    break;

  }

}

Continue Example

int i = 0;

while (i < 10) {

  if (i == 4) {

    i++;

    continue;

  }

  cout << i << "\n";

  i++;

}