forLoops

`for` Loops

A for loop is also called a counting loop, because it repeatedly executes a block of code a certain number of times. The basic syntax for a for loop is: :


for (counter = initial-expression; logical-expression; change-counter)
        statement

A for loop is executed as follows:

Execute the counter = initial expression. This happens only the first time through the loop.
Evaluate the logical expression:
If it is true
- Execute the statement inside the for loop.
- Return to the top of the loop and execute the change-counter part.
- Then back to "Evaluate the logical expression."

This is repeated until the logical expression evaluates to false, then execution falls through to the next statement.

The statement repeated by the for loop can also be a compound statement:


for (counter = initial-expression; logical-expression; counter-change)
{
    statement
    statement
    ...
}

A real section of code is a little clearer:


for (i = 1; i <= 10; i++)
{
    statement
    statement
    ...
}

In the for loop above, how many times will the statements be repeated?

The first part of the for loop, i = 1; initializes the object i to the value 1.

The next part, i <= 10; contains the logical expression that will be evaluated each time through the loop. The loop will continue until this expression evaluates to false.

The last part, i++ increments i by adding 1 to it (it could also have been written as i = i + 1 or i += 1).

At the conclusion of the loop, i has the value 11.

Typically, the variable i should be of type int, but for loops can be written with floats or doubles, if appropriate.

You can change the counter in any way you would like. For instance, you could write a for loop that counts by 5s:


for (i = 5; i <= 30; i = i + 5)
    statement

You can also use a for loop that counts down. How would you do it?

Tips on for Loops

for Loops

`for` Loops