Relational operators in C ( == , < , <= , > , >=)

#include <stdio.h>
void main()
{
 int a = 21;
 int b = 10;
 int c ;
 if( a == b )
 {
  printf("Line 1 - a is equal to b\n" );
 }
 else
 {
  printf("Line 1 - a is not equal to b\n" );
 }
 if ( a < b )
 {
  printf("Line 2 - a is less than b\n" );
 }
 else
 {
  printf("Line 2 - a is not less than b\n" );
 }
 if ( a > b )
 {
  printf("Line 3 - a is greater than b\n" );
 }
 else
 {
  printf("Line 3 - a is not greater than b\n" );
 }
/* Lets change value of a and b */
 a = 5;
 b = 20;
 if ( a <= b )
 {
  printf("Line 4 - a is either less than or equal to b\n" );
 }
 if ( b >= a )
 {
  printf("Line 5 - b is either greater than or equal to b\n" );
 }
}
output :
Line 1 - a is not equal to b
Line 2 - a is not less than b
Line 3 - a is greater than b
Line 4 - a is either less than or equal to b
Line 5 - b is either greater than or equal to b