下列程序的主要功能是（）。  #include   main( ) {      FILE *in,*out;      char ch,infile[10],outfile[10];      printf(“Enter the infile name:/n”);      scanf(“%s”,infile);      printf(“Enter the outfile name:/n”);      scanf(“%s”,outfile);      if((in=fopen(infile, “r”))==NULL){          printf(“Cannot open infile/n”);          exit(0);      }  if((out=fopen(outfile, “w”))==NULL){          printf(“Cannot open outfile/n”);          exit(0);      }      while(!feof(in))          fputc(fgetc(in),out);      fclose(in);      fclose(out);  }