# The need for loops

While solving certain programming problems, some blocks of code need to be executed repeatedly. The repetition of the same code until a particular condition is met justifies the need of *for loops* as a whole.

# Syntax of a for loop

The **for loop** is a special kind of loop that only repeats the block of code it contains for a specific number of times. The number of repetitions is defined by a conditional statement within the loop. Let's look at the syntax for declaring a loop to better understand how this works. 
 

  for(controlVariable; condition; changingControl){
    //body of for loop
  }

Now let's look at each section of the for loop:

* The `controlVariable` is the variable defined that will be used to initialize the loop counter i.e. the number of times the loop will run.

* The `condition` is the statement on the basis of which the loop will be evaluated. Given that the statement returns *false*, the loop will no longer run.

* The `changingControl` is the statement that will either *increment*, *decrement* or change the `controlVariable` for the next loop run.

* The curly braces, `{}`, contain the code block that is to be executed.

# How does a for loop work?

The illustration below shows the life cycle of the for loop and how it evaluates statements to run itself

Now that we know why we need a for loop and how it works, lets look at an example to re-inforce what we have learnt!

#include <stdio.h>

int main() {
  // your code goes here
  int sum =0;
  for(int a=0;a<10;a++){
    sum= sum+a;
    printf("%d\n",sum);
    

  }
}

In the code above, let's see which part is what:

* Here the `controlVariable` is the `int a = 0` declaration which defines the initializer value for the *for loop*.
* The `condition` in this case is the `a < 10` statement; if `a` is less than *5* the loop will continue to run, otherwise it will terminate.
* `changingControl` is the expression `a++` indicating that before the next run of the loop, *increase the value of a by 1*.
* The body of the loop to be executed each time is the block of code that adds `a` to `sum` and then prints the value of `sum`.
* This entire process of checking the `condition` and subsequent actions is repeated once the code body executes.

Using for loops in C

The need for loops

Syntax of a for loop

How does a for loop work?

Applying theory to example