Write C programming syntax for, while, do while loops.

Repetitive statements in Programming

You must be trying to write repetitive statements in C programming and want to more. C programing uses a structural blocks called loops. There are three types of loops in C. They are "for" loop, "while" loop and "do-while" loop. Learn more about loops : Repetitive statements and loops in C programming.

For Loop syntax

For loop stars with "for" keyword and three parameters enclosed within a first bracket. Three parameters are -

  1. Initialization statements
  2. Condition of the looping
  3. Repeat steps
Loop statements are enclosed with a second bracket. This bracket in not needed if there is only one statement.

for (
  <initial statement(s)>;
  <Condition expression>;
  <Repeat step(s)>
  )
{
  <Loop statement(s)>;
}

For loop Diagram

For loop - Examples

for (int i = 0; i < 10; i++)
{
  printf("Iteration %d\n", i);
}

for (int i = 0, j = 2; i < 10; i++, j += 2)
{
  printf("2 x %d = %d\n", i + 1, j);
}

for (; ;)
{
  printf("I am infinite loop\n");
  delay(1000);
}

While Loop syntax

While loop stars with "while" keyword and is one condition for the loop which is enclosed within a first bracket. Loop statements are enclosed with a second bracket. This bracket in not needed if there is only one statement.

while (<Condition expression>)
{
  <Loop statement(s)>;
}

While loop Diagram

While loop - Examples

int i = 0;
while(i < 10)
{
  printf("Iteration %d\n", i);
  i++;
}

while (TRUE)
{
  printf("I am infinite loop\n");
  delay(1000);
}

Do-While Loop syntax

Do While loop stars with no condition and loop statements are enclosed with second bracket. However "while" keyword along with the condition is placed at the end of the loop statement. Thus entry to the loop is unconditional but the exit or the continuation is decided by the condition expression.

do
{
  <Loop statement(s)>;

}while (<Condition expression>);

Do-While loop Diagram

Do-While loop - Examples

int i = 0;
do
{
  printf("Iteration %d\n", i);
  i++;
} while (i < 10);

do
{
  printf("I am infinite loop\n");
  delay(1000);
}while (TRUE)

Important notes

Initial statement(s) - these are one or multiple statements (use comma in between). Often contains initialization of counter variables.

Repeat step(s) - these are one or multiple statements. Often contains counter operation on variables like increment, decrement etc.

Condition statement - is however only one condition statement.

Condition statement - for loop will be an infinite if it is blank.

Condition expression - while/do-while loop will be an infinite if it is a always TRUE.

Loop statement(s) - these statements are tasks in each steps. Counter variables are often used in the steps.

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Further readings

How to write repetitive statements in C? [for, while, do while example, flowchart]
Repetitive tasks in programming. Repetitive statements and loop statements. How to write loop statements. For while do-while loop, syntax and example code.

How to convert for a loop to while loop, vice versa?[GUIDE]
Convert for loop to while loop and vice versa. Understand for, while, do-while loops and write code properly. Also understand on how to convert for, while, do-while to other loops

When is do-while loop preferred over while loop, Give example?
Understand importance and need of do-while loop. How preferred over while loop, Use of do while over while loop. Give example do while vs while usecase

Write infinite loop statements for 'while', 'do-while' and 'for'?
What is an infinite loop in programming? Need of infinite loop. Write infinite loop statements in C. Example of infinite loop 'for' 'while', 'do-while'.

How to break a loop? How to skip loop iterations with continue? [example and flowchart]
Understanding C continue and break keyword with flowchart and practical example source code. Where to put break or continue in for loop, while loop, do while loop

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