咋算加法都得0，应该没啥问题啊

#include<stdio.h>
int main()
{
    char command_begin;
    double first_number;
    char character;
    double second_number;
    double value;
    printf("简单计算器程序\n---------\n");
    printf("在'>'提示后输入一个命令字符\n");
    printf("是否开始？（Y/N）>");
    scanf("%c",&command_begin);
    while (command_begin=='Y'||command_begin=='y')
    {
        /* 当接受Y/y命令时执行计算器程序*/
        printf("请输入一个简单的算式：");
        scanf("%1f%c%1f",&first_number,&character,&second_number);/* 输入一个算式，如3+5*/
        switch(character)
        {
            case'+':
                value=first_number+second_number;
                printf("等于%1f\n",value);
                break; 
            case'-':
                value=first_number-second_number;
                printf("等于%1f\n",value);
                break; 
            case'*':
                value=first_number*second_number;
                printf("等于%1f\n",value);
                break; 
            case'/':
                while(second_number==0)
                {
                    printf("除数为零，请输入一个算式：");
                    scanf("%1f%c%1f",&first_number,&character,&second_number);
                }
                value=first_number/second_number;
                printf("等于%f\n",value);
                break;
                default:
                printf("非法输入！\n");
        }
        printf("是否继续运算？（Y/N>）");
        fflush(stdin);
        scanf("%c",&command_begin);

    }
    printf("程序退出！\n");
}

scanf里面是%lf不是%1f ,是字母l，不是数字1，%lf表示double类型

#include<stdio.h>
int main()
{
    char command_begin;
    double first_number;
    char character;
    double second_number;
    double value;
    printf("简单计算器程序\n---------\n");
    printf("在'>'提示后输入一个命令字符\n");
    printf("是否开始？（Y/N）>");
    scanf("%c",&command_begin);
    while (command_begin=='Y'||command_begin=='y')
    {
        /* 当接受Y/y命令时执行计算器程序*/
        printf("请输入一个简单的算式：");
        scanf("%lf%c%lf",&first_number,&character,&second_number);/* 输入一个算式，如3+5*/
        switch(character)
        {
            case'+':
                value=first_number+second_number;
                printf("等于%1f\n",value);
                break; 
            case'-':
                value=first_number-second_number;
                printf("等于%1f\n",value);
                break; 
            case'*':
                value=first_number*second_number;
                printf("等于%1f\n",value);
                break; 
            case'/':
                while(second_number==0)
                {
                    printf("除数为零，请输入一个算式：");
                    scanf("%lf%c%lf",&first_number,&character,&second_number);
                }
                value=first_number/second_number;
                printf("等于%f\n",value);
                break;
            default:
                printf("非法输入！\n");
        }
        printf("是否继续运算？（Y/N>）");
        fflush(stdin);
        scanf("%c",&command_begin);
 
    }
    printf("程序退出！\n");
}