#include<stdio.h>

int main(int argc, char** argv) {

  char* input_filename = "upper.c";
  char* output_filename = "double.txt";
  FILE* iptr;
  FILE* optr;
  char c;

  if (argc > 1)
    input_filename = argv[1];
  
  if (argc > 2)
    output_filename = argv[2];

  iptr = fopen(input_filename,"r");
  optr = fopen(output_filename,"w");

  while((c = getc(iptr)) != EOF) {
    putc(c,optr);
    if (c == '\n')
      putc(c,optr);
  }
  
  fclose(iptr);
  fclose(optr);
}