程序代码：

#include <stdio.h>
int main()
{
    FILE *fa,*fb;
    int n;
    fa=fopen("a.dic.txt","r");
    fb=fopen("user.out.txt","w");
    if(fa==NULL||fb==NULL)
    {
        printf("Can not open file!\n");
        exit(0);
    }
    fscanf(fa,"%d",&n);
        n=n*n;
    fprintf(fb,"%d",n);
    fclose(fa);
    fclose(fb);
    return 0;
}