• switch语句会匹配多个表达式。
• 如果想匹配一个，需要加关键字，case 一旦匹配上某一个，则结束匹配。 ```cpp

  include

int main() { char c; c = getchar();

switch (c) //参数只能是整型变量
{
case '1':
    printf("OK\n");
    break;//switch遇到break就中断了
case '2':
    printf("not OK\n");
    break;
default://如果上面的条件都不满足，那么执行default
    printf("are u ok?\n");
}
return 0;

}

```cpp
#include <stdio.h>
#include <stdbool.h>
#define ADD '+'
#define SUB '-'
#define MULTIPLY '*'
#define DIVIDE '/'
#define REM '%'
int main() {
    int left;
    int right;
    while (true) {
        char operator;
        printf("Please input an expression: \n");
        scanf("%d %c %d", &left, &operator, &right);
        int result;
        switch (operator) {
            case ADD:
                result = left + right;
                break;
            case SUB:
                result = left - right;
                break;
            case MULTIPLY:
                result = left * right;
                break;
            case DIVIDE:
                result = left / right;
                break;
            case REM:
                result = left % right;
                break;
            default:
                printf("Unsupported operation: %c\n", operator);
                return 1;
        }
        printf("Result: %d\n", result);
    }
    return 0;
}