試試下麵的例子就明白了所有C++提供的關係運算符。

複製下麵的C++程序並粘貼到test.cpp 文件編譯並運行此程序。

#include <iostream>
using namespace std;

main()
{
   int a = 21;
   int b = 10;
   int c ;

   if( a == b )
   {
      cout << "Line 1 - a is equal to b" << endl ;
   }
   else
   {
      cout << "Line 1 - a is not equal to b" << endl ;
   }
   if ( a < b )
   {
      cout << "Line 2 - a is less than b" << endl ;
   }
   else
   {
      cout << "Line 2 - a is not less than b" << endl ;
   }
   if ( a > b )
   {
      cout << "Line 3 - a is greater than b" << endl ;
   }
   else
   {
      cout << "Line 3 - a is not greater than b" << endl ;
   }
   /* Let's change the values of a and b */
   a = 5;
   b = 20;
   if ( a <= b )
   {
      cout << "Line 4 - a is either less than 
                                    or euqal to  b" << endl ;
   }
   if ( b >= a )
   {
      cout << "Line 5 - b is either greater than 
                                    or equal to b" << endl ;
   }
   return 0;
}

讓我們編譯和運行上麵的程序，這將產生以下結果：

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 euqal to  b
Line 5 - b is either greater than or equal to b