#include <stdio.h>
#define ROWS 4
#define COLS 4
int nums[ROWS][COLS]={{1000,1000,1000,1000},
                 {900,500,400,100},
                 {90,50,40,10},
                 {9,5,4,1}};
char *roms[ROWS][COLS]={{"m","m","m","m"},
                      {"cm","d","cd","c"},
                      {"xc","l","xl","x"},
                      {"ix","v","iv","i"}};

main(int argc,char *argv[ ])
{
    int low,high;
    char roman[25];

    if(argc<2)
    {    printf("Usage:roman decimal_number\n");/*运行程序需带整数参数*/
         exit(0);
    }
    high=low=atoi(argv[1]);/*将第一个参数转换成整数*/
    checknum(low);
    if(argc>2)
    {/*带两个参数*/
    high=atoi(argv[2]);
    checknum(high);
    if(low>high)
        {
            low=high;
            high=atoi(argv[1]);
        }
    }
    else
        low=1;
    for(;low<=high;low++)
    {
        to_roman(low,roman);
        printf("%d\t%s\n",low,roman);
    }
}

checknum(int val)/*检查参数合理性*/
{
    if(val<1||val>9999)
    {
        printf("The number must be in range 1..9999.\n");
        exit(0);
    }
}
to_roman(int decimal,char roman[ ])/*将整数转换成罗马数字表示*/
{
    int power,index;
    roman[0]='\0';
    for(power=0;power<ROWS;power++)
        for(index=0;index<COLS;index++)
            while(decimal>=nums[power][index])
            {
                strcat(roman,roms[power][index]);
                decimal-=nums[power][index];
            }
}

其中主函数的两个参数int argc,char *argv[ ]的作用是什么？代表什么意思啊！
请大家回复这个问题！