计划让程序做如下的检测：

附上代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char * Mystrrev (char * str );
int main()
{
    char str[33];
    int System;
    int n,x,y;
    
     FILE *fp;
     if ((fp = fopen ("D:\\wenjian.txt", "a+")) == NULL)
      {
         printf("打开文件失败\n");
         exit(1);
      }
    printf("请输入本次填充数据的进制：（2~9）\n");
    printf("进制 :");
    scanf("%d",&System);
    printf("请输入本次生成数据的组数：(0`n)\n");
    printf(" n = ");
    scanf("%d",&n);
    printf("请输入本次生成数据的数组大小：\n");
    printf(" 行 x= ");
    scanf("%d",&x);
    printf(" 列 y= ");
    scanf("%d",&y);

   int Data[n][x][y];
   for (int i = 0 ; i < n ; i++ )
    {
        itoa(i, str, System);
        int Str_length = strlen(str);
        char str_tem[33];
        char str_tem1[33];
        memset(str_tem,'0',33);
        int Data_x_length = (x-1)/2+(x-1)%2;
        if ( Data_x_length >= Str_length) str_tem[Data_x_length - Str_length] ='\0';
        else
        {
            printf("数组太小,请检查你的设置参数!");
            return -1;
        }
        strcat(str_tem,str);
        strcpy( str_tem1, str_tem);
        Mystrrev (str_tem1);
        if (x%2)
             strcat( str_tem1, str_tem);
        else
        {
            str_tem1[strlen(str_tem1)-1] ='\0';
            strcat( str_tem1, str_tem);
        }
        for (int ay=0;ay < y; ay++)
            Data[i][0][ay] = ay+1;
        for (int ax=1;ax < x;ax++)
            for (int ay=0;ay < y;ay++)
                 Data[i][ax][ay] =str_tem1[ax-1]- '0';
   }
    for (int an=0;an < n;an++)
    {
        fprintf(fp,"n = %4d\n",an);
        for (int ax = 0;ax < x ; ax++)
        {
            for (int ay = 0;ay < y;ay++)
                 fprintf(fp,"%4d",Data[an][ax][ay]);
            fprintf(fp,"\n");
        }
        fprintf(fp,"\n");
       
               }
    fclose(fp);
    return 0;
}
char * Mystrrev (char * str )
{
    char *start = str;
    char *left = str;
    char ch;
    while (*str++);
    str -= 2;
    while (left < str)
    {
        ch = *left;
        *left++ = *str;
        *str-- = ch;
    }
    return(start);
}

为啥当代码运行到
    请输入本次生成数据的数组大小 行
选择第20行（含21行以后的行数）的时候，输出的文件是空文件呢？文件没有内容。这个文件不应该是空文件哦。