More Operators

There are variety of operators which are frequently used with while. To illustrate their usage let us consider a problem wherein numbers from 1 to 10 are to be printed on the screen. The program for performing this task can be written using while  in the following different ways:

(a)  main( )
{
     int   i = 1 ;
     while ( i <= 10 )
 {
           printf ( "%d\n", i ) ;
           i = i + 1 ;
 }
}

(b)  main( )
{
  int   i = 1 ;
     while ( i <= 10 )
 {
           printf ( "%d\n", i ) ;
  i++ ;
 }
}

 Note that the increment operator ++ increments the value of i by 1, every time the statement i++ gets executed. Similarly, to reduce the value of a variable by 1 a decrement operator -- is also available. 
However, never use n+++ to increment the value of n by 2, since C doesn’t recognize the operator +++.

(c)  main( )
{
     int   i = 1 ;
     while ( i <= 10 )
 {
           printf ( "%d\n", i ) ;
           i += 1 ;
 }
}

 Note that +=  is a compound assignment operator. It increments the value of i by 1. Similarly, j = j + 10 can also be written as j += 10. Other compound assignment operators are -=, *=, / = and %=.

(d)  main( )
{
     int  i = 0 ;
     while ( i++ < 10 )

printf ( "%d\n", i ) ;
}

 In the statement while ( i++ < 10 ), firstly the comparison of value of i with 10 is performed, and then the incrementation of i takes place. Since the incrementation of i happens after its usage, here the ++ operator is called a post-incrementation operator. When the control reaches printf ( ),  i has already been incremented, hence i must be initialized to 0. 

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

 In th statement    e  while ( ++i <= 10 ), firstly incrementation of i takes place, then the comparison of value of i with 10 is performed. Since the incrementation of i happens before its usage, here the ++ operator is called a pre- incrementation operator