while loop in C

While loop is also known as a pre-tested loop. In general, a while loop allows a part of the code to be executed multiple times depending upon a given boolean condition. It can be viewed as a repeating if statement. The while loop is mostly used in the case where the number of iterations is not known in advance.

Syntax of while loop in C language

The syntax of while loop in c language is given below:

    
        while(condition){  
            //code to be executed  
            }

Example of the while loop in C language

Let's see the simple program of while loop that prints table of 1.

    
        #include  
            int main(){    
            int i=1;      
            while(i<=10){      
            printf("%d n",i);      
            i++;      
            }  
            return 0;  
            }

Output

1 2 3 4 5 6 7 8 9 10

Program to print table for the given number using while loop in C


    #include  
        int main(){    
        int i=1,number=0,b=9;    
        printf("Enter a number: ");    
        scanf("%d",&number);    
        while(i<=10){    
        printf("%d n",(number*i));    
        i++;    
        }    
        return 0;  
        }

Output

Enter a number: 50 50 100 150 200 250 300 350 400 450 500 Enter a number: 100 100 200 300 400 500 600 700 800 900 1000

Properties of while loop

A conditional 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.

Example 1:

    
        #include  
            void main ()  
            {  
                int j = 1;  
                while(j+=2,j<=10)  
                {  
                    printf("%d ",j);   
                }  
                printf("%d",j);  
            }

Output

3 5 7 9 11

Example 2:

        
            #include  
                void main ()  
                {  
                    while()  
                    {  
                        printf("hello Javatpoint");   
                    }  
                }

Output

compile time error: while loop can't be empty

Example 3:

            
                #include  
                    void main ()  
                    {  
                        int x = 10, y = 2;  
                        while(x+y-1)  
                        {  
                            printf("%d %d",x--,y--);  
                        }  
                    }

Output

infinite loop

Infinitive while loop in C

If the expression passed in while loop results in any non-zero value then the loop will run the infinite number of times.

            
                while(1){  
                    //statement  
                    }