C for Loop

In this tutorial, you will learn to make for loop in C programming with the help of examples.

In programming, a loop is used to repeat a block of code until the predetermined condition is met.

C programming has three types of loops:

for loop
while loop
do..while loop
We will learn about for loop in this tutorial. In the next tutorial, we will learn about while and do…while loop.

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for Loop

The syntax of the for loop is:

for (initializationStatement; testExpression; updateStatement)
{
    // statements inside the body of loop
}

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How for loop functions?

The initialization statement is executed just a single time.

Then, the test expression is evaluated. In the event that the test articulation is assessed to bogus, the for circle is ended.

However, if the test expression is evaluated to valid, explanations inside the collection of for circle are executed, and the update expression is updated.

Again the test expression is evaluated.

This process goes on until the test expression is false. When the test expression is false, the loop terminates.

To learn more about test expression (when the test expression is evaluated to true and false), check out relational and logical operators.

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for loop Flowchart

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Example 1: for loop

// Print numbers from 1 to 10
#include <stdio.h>

int main() {
  int i;

  for (i = 1; i < 11; ++i)
  {
    printf("%d ", i);
  }
  return 0;
}

Output

1 2 3 4 5 6 7 8 9 10

i is initialized to 1.
The test expression i < 11 is evaluated. Since 1 less than 11 is true, the body of for loop is executed. This will print the 1 (value of i) on the screen.
The update statement ++i is executed. Now, the value of i will be 2. Again, the test expression is evaluated to true, and the body of for loop is executed. This will print 2 (value of i) on the screen.
Again, the update statement ++i is executed and the test expression i < 11 is evaluated. This process goes on until i becomes 11.
When i becomes 11, i < 11 will be false, and the for loop terminates.

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Example 2: for loop

// Program to calculate the sum of first n natural numbers
// Positive integers 1,2,3...n are known as natural numbers

#include <stdio.h>
int main()
{
    int num, count, sum = 0;

    printf("Enter a positive integer: ");
    scanf("%d", &num);

    // for loop terminates when num is less than count
    for(count = 1; count <= num; ++count)
    {
        sum += count;
    }

    printf("Sum = %d", sum);

    return 0;
}

Output

Enter a positive integer: 10
Sum = 55

The value entered by the client is put away in the variable num. Assume, the client entered 10.

The count is instated to 1 and the test expression is evaluated. Since the test articulation count<=num (1 not exactly or equivalent to 10) is valid, the group of for circle is executed and the estimation of entirety will equivalent to 1.

Then, the update statement ++count is executed and the check will equivalent to 2. Once more, the test expression is evaluated. Since 2 is also under 10, the test expression is evaluated to valid and the body of for circle is executed. Presently, the entirety will equal to 3.

This process goes on and the sum is calculated until the count reaches 11.

When the count is 11, the test expression is evaluated to 0 (false), and the loop terminates.

Then, the value of the sum is printed on the screen.

We will learn about while loop and do…while loop in the next tutorial.

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C Flow Control