关系运算符

下表列出了所有C语言支持的关系运算符。假设变量A=10和变量B=20，则：

操作符	描述	示例
==	检查两个操作数的值是否相等，如果是的话那么条件为真。	(A == B) 不为 true
!=	检查两个操作数的值是否相等，如果值不相等，则条件变为真。	(A != B) 为 true
>	检查左边的操作数的值是否大于右操作数的值，如果是的话那么条件为真。	(A > B) 不为 true
<	检查左边的操作数的值是否小于右操作数的值，如果是的话那么条件为真。	(A < B) 为 true
>=	检查左边的操作数的值是否大于或等于右操作数的值，如果是的话那么条件为真。	(A >= B) 不为  true
<=	检查左边的操作数的值是否小于或等于右操作数的值，如果是的话那么条件为真。	(A <= B) 为 true

示例

试试下面的例子就明白了所有的C语言编程提供的关系运算符：

#include <stdio.h>

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

   if( a == b )
   {
      printf("Line 1 - a is equal to b
" );
   }
   else
   {
      printf("Line 1 - a is not equal to b
" );
   }
   if ( a < b )
   {
      printf("Line 2 - a is less than b
" );
   }
   else
   {
      printf("Line 2 - a is not less than b
" );
   }
   if ( a > b )
   {
      printf("Line 3 - a is greater than b
" );
   }
   else
   {
      printf("Line 3 - a is not greater than b
" );
   }
   /* 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
" );
   }
   if ( b >= a )
   {
      printf("Line 5 - b is either greater than  or equal to b
" );
   }
}

当编译和执行上面的程序就产生以下结果：

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

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