豪华版计算器，如果加上图形库就跟好了(下面省略没写)。

#include <stdio.h>

int get_option();
void print_result(int num1,int num2,int result,int option);

int main(void)
{
    int done = 0;
    int option,num1,num2,result;
    
    while(!done)
    {
        option = get_option();
        if(option == 5)
        {
            done = 1;
        }
        else {
            do {
                printf("\n请输入两个数：");
                scanf("%d %d",&num1,&num2);
                if(option == 4 && num2 == 0)
                {
                    printf("\n对不起，除数不能为零");
                } 
                else {
                    switch(option){
                        case 1:
                            result = num1 + num2;
                            break;
                        case 2:
                            result = num1 - num2;
                            break;
                        case 3:
                            result = num1 * num2;
                            break;
                        case 4:
                            result = num1 / num2;
                    }
                    print_result(num1,num2,result,option);
                }
            }while(option == 4 && num2 == 0);
        }
    }

    return 0;
}

int get_option()
{
    int option;
    do
    {
        printf("\n ****************");
        printf("\n *    1.加法    *");
        printf("\n *    2.减法    *");
        printf("\n *    3.乘法    *");
        printf("\n *    4.除法    *");
        printf("\n *    0.退出    *");
        printf("\n ****************");

        printf("\n请输入您需要的功能：");
        scanf("%d",&option);

        if(option <1 || option > 5)
        {
            printf("对不起您输入的数字有误，请重新输入。\n");
        }
    }while(option <1 || option > 5);

        return option;
}

void print_result(int num1,int num2,int result,int option){
    char operator;
    switch(option){
        case 1:
            operator = '+';
            break;
        case 21:
            operator = '-';
            break;
        case 3:
            operator = '*';
            break;
        case 4:
            operator = '/';
            break;
    }
    printf("\n** %d %c %d = %d **\n",num1,operator,num2,result);
}