While Loop in C

While Loop in C

In while loop First check the condition if condition is true then control goes inside the loop body other wise goes outside the body. while loop will be repeats in clock wise direction.

Execution Flow of While Loop

Assignment;
while(condition)
{
statements;
............
Increment or Decrements (++ or --);
}

Note: If while loop condition never false then loop become infinite loop.

Here, statement(s) may be a single statement or a block of statements. The condition may be any expression, and true is any nonzero value. The loop iterates while the condition is true.
When the condition becomes false, the program control passes to the line immediately following the loop.

When while loop is use ?

When we do not know about how many times loops are perform or iteration of loop is unknown.

Flow Diagram

#include<stdio.h>
#include<conio.h>

void main()
{
int i;
clrscr();
i=1;
while(i<5)
{
printf("\n%d",i);
i++;
}
getch();
}

Output:
1
2
3
4

Execution process of while loop is slower than for loop.

Infinite While Loop

#include<stdio.h>
#include<conio.h>

void main()
{
  int var = 6;
  while (var >=5)
   {
    printf("%d", var);
    var++;
   }
getch();
}

var will always have value >=5 so the loop would never end.

Properties of While Loop

• In while loop onditional expression is used to check the condition. The statements defined inside the while loop will repeatedly execute until the given condition fails.
• The condition will be true if it returns 0. The condition will be false if it returns any non-zero number.
• In while loop, the condition expression is compulsory.
• Running a while loop without a body is possible.
• We can have more than one conditional expression in while loop.
• If the loop body contains only one statement, then the braces are optional.

While Loop Can't be Empty

#include<stdio.h>
#include<conio.h>

void main()
{
while()  
    {  
     printf("Hello World!");   
    }  
getch();
}

compile time error: while loop can't be empty