书上的程序看不懂啊，求个注释，有劳，谢谢大家
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(void)
{
   int n,m,t,flag,i,j,*p;
   int a[4][13];
   srand((unsigned)time(NULL));
   for(i=0;i<4;i++)
       for(j=0;j<13;j++)
           a[i][j]=0;
       t=1;
       while(t<=13)
       {
           n=rand()%4;
           printf("%d ",n);
           m=rand()%13;
           flag=1;
           if(a[n][m]==1) flag=0;
           if(flag) {a[n][m]=1;t++;}
       }
       p=a[0];
       t=0;
       for(i=0;i<4;i++)
       {
           if(i==0) printf("%s","黑桃:");
           else if(i==1) printf("%s","红桃:");
           else if(i==2) printf("%s","梅花:");
           else  printf("%s","方片:");
           for(j=0;j<13;j++)
           if(*(p+13*i+j)==1)
               {
                   if(j+1==1) printf("%3c",'A');
                       else if(j+1==11) printf("%3c",'J');
                       else if(j+1==12) printf("%3c",'Q');
                       else if(j+1==13) printf("%3c",'K');
                       else printf("%3d",j+1);
               }
           printf("\n");
       }
       return 1;
}