C integer calculator (implemented with the parameters of the main function)

1. Topic

Use the parameters of the main function to implement an integer calculator. The program can accept three parameters. The first parameter "-a" option performs addition, "-s" option performs subtraction, "-m" option performs multiplication, "-d" option ” option performs division, and the last two arguments are operands.

2. Program code

#define _CRT_SECURE_NO_WARNINGS 1

#include <stdio.h>
#include <Windows.h>
#include <stdlib.h>

int Add(int x, int y)//两个数相加
{
    return x + y;
}

int Sub(int x, int y)//两个数相减
{
    return x - y;
}

int Mul(int x, int y)//两个数相乘
{
    return x * y;
}

int Div(int x, int y)//两个数相除
{
    return x / y;
}

int main(int argc, char* argv[], char* envp[])
{
    if (argc != 4)//argc表示的是命令行参数的个数（包含文件名），要求为4个，若输入的不为4个，则输入有误
    {
        printf("input error!\n");
        return 0;
    }

    int x = atoi(argv[2]);//argv是命令行参数中的每个参数
    //aito函数功能是把字符串转成数字，例如atoi('123')结果就为123，要引头文件stdlib.h
    int y = atoi(argv[3]);
    int ret = 0;

    switch (*(argv[1] + 1))//argv取到的是'-'的地址，加一就为后面字母的地址，再解引用
    {
    case 'a':
        ret = Add(x, y);
        break;
    case 's':
        ret = Sub(x, y);
        break;
    case 'm':
        ret = Mul(x, y);
        break;
    case 'd':
        ret = Div(x, y);
        break;
    }

    printf("%d\n", ret);

    system("pause");
    return 0;
}

3. Execution results