主要有两行看不懂~
为何---sum+=(a[i]-'0')*(8-i);
       if(code==(a[7]-'0'))  後面要加-'0'呢?

程序如下:
#include<stdio.h>
main()
{
      char number[9];
      printf("enter the uniform number:");
      scanf("%s",number);
      if(valid(number));
      printf("the number %s is valid\n",number);
      else
      printf("the number &s is invalid\n",number);
}

int valid(char a[])
{
    int i,sum,code;
    sum=0;
    for(i=0,i<=6;i++)
    sum+=(a[i]-'0')*(8-i);
    code=sum%10;
    if(code==(a[7]-'0'))
       return (1);
    else
       return (0);
}

原来是要把字串转换成数值~~
谢谢~~