Sunday 30 September 2012

Decision making looping

The ‘C’ language provides three loop constructs for performing loop operations they are

1.      The while statement
2.      Do-while statement
3.      The for statement

The While Statement : This type of loop is also called an entry controlled, is executed and if is true then the body  of the loop is executed this process repeated until the boolean expression becomes false. Ones it becomes false the control is a transferred out the loop. The general form of the while statement is

                        While (boolean expression)
{
                                    body of the loop;
}
Flow chart:


Ex :                 i = 1;
                        While(I<=5)
{   printf(“%d”,i);
i++; }

In the above example the loop with be executed until the condition is false

Do-While Statement : This type of loop is also called an exist controlled loop statement.
i.e.., The boolean expression  evaluated at the bottom of the loop and if it is true then body of the loop executed again and again until the boolean expression becomes false. Ones it becomes false the control is do-while statement is

                        Do
                        {
                                    body of the loop ;
                        }
                        while ( boolean expression)

Flow chart :     
Ex :                 i = 1;
                        Do
                        {
                        printf(“%d”,i);
                        i++;
                        }
                        While(i<=5)

While  statement                                     Do-while statement        

1. It is an entry controlled loop.                       1. It is an exit controlled looping.                                                                                      
2. If boolean expression is false                        2. The body of the loop executed
then  the body of the loop   never                     atleast ones even  be executed if the
be executed.                                                      Boolean expression is either true or false

The  For Statement : The for loop is another entry control led loop that provides a more concise loop control structure the general form of the for loop is

                                    For ( initialisation; test condition; increment)
                                    {
                                                body of the loop;
                                    }

 Where initialization is used to initialize some parameter that controls the looping action, ‘test condition’ represents  if that condition  is true  the body of the loop is executed, otherwise the loop is terminated After evaluating information  and the new value of the control variable is again tested the loop condition. If the condition is satisfied the body of the  loop is again executed it this process continues until the value of the control variable false to satisfy the condition.


Flow chart :      

Ex :     for (I=1; I<=5; I++)
{                                                          Output :   1  2  3  4  5
printf(“%d”,i);
            }

Jumping From The Loops :

Break Statement : The break statement can be accomplish by using to exist the loop. when break is encountered inside  a loop, the loop is immediately exited and the program continues with the statement which is followed by the loop. If nested loops then the break statement inside one loop transfers the control to the next outer loop.

Ex :                 for (I=1; I<5; I++)
                        {                                                          Output :          1   2   3
if ( I == 4)                              
break;
printf(“%d”,i);
}

Continue Statement : The continue statement  which is like break statement. Its work is to skip the present statement  and continues  with the next iteration of the loop .

Ex :                 for (I=1; I<5; I++)
                        {                                                          Output :          1   2   4   5
if ( I == 3)                              
continue;
printf(“%d”,i);
}

In the above example when I=3  then the continue  statement  will  rise and skip statement in the loop and continues for the next iteration i.e.., I=4.

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