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 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);
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
}
The example below will print the numbers 0 to 4:
Example
for (int i = 0; i < 5; i++) {
cout << i << "\n";
}
Example explained
This example will only print even values between 0 and 10:
Example
for (int i = 0; i <= 10; i = i + 2) {
cout << i << "\n";
}
Example
for (int i = 0; i < 10; i++) {
if (i == 4) {
break;
}
cout << i << "\n";
}
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";
}
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++;
}
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