## 关系运算符

== 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

```#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
" ); } }```

```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```