Print binary numbers to disk file, problem

Could somebody tell how I can actually write the input and output to a disk file?
When I open the disk file, it only has the description, but not the data

Code:

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#include <stdio.h>
#include <conio.h>
#include <process.h>

int main(void)
{
  FILE *test2_file;
  int num;
  int no_bits;
  int reply = 0;


  test2_file = fopen ("decimal2binary.txt", "w");
  fprintf (test2_file, "This is the content of the decimal2binary file.");

  do
  {
      system("cls");
      printf("\n                Welcome to the DECIMAL to BINARY program!");
      printf("\nThis program accepts a decimal number and converts it into a ");
      printf("binary number.\nIt also states how many bits the number occupies.");
      printf("\n\nEnter a number: ");
      scanf("%d",&num);
      no_bits=count_bits(num);
      printf("The number of bits is %d",no_bits);
      bin_print(num,no_bits);
      printf("\n");
      printf("Would you like to input another number (y/n): ");
      reply = getche();
      if ((reply != 'n') && (reply != 'N'))
        {
            printf("\n\nTo terminate inputs you need to reply N or n -");
            printf(" your reply was %c", reply);
        }
  }
  while ((reply == 'y') || (reply == 'Y'));
  fclose(test2_file);

  printf("\n\n");
  printf("Bye friends!\n");
  system("pause");
}

count_bits(int n)
{
  int i = 0;

  for (;n!=0; n = n >> 1)
  i++;

  return(i);
}


bin_print(int x, int n_bits)
{
  int j;

  printf("\nno. %d in binary: ",x);

  for( j = n_bits - 1; j >= 0; j--)
  printf("%i",( x >> j ) & 01);
}

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man fprintf, fscanf, fgets

Precisely. printf is writing to stdout, i.e. the console screen. fprintf will write to the open file.

Quote:

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Originally Posted by Guti14

When I open the disk file, it only has the description, but not the data

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Code:

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test2_file = fopen ("decimal2binary.txt", "w");

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You're re-creating the file, therefore the data is erased...
Should be:

Code:

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test2_file = fopen ("decimal2binary.txt", "r+");

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to have both read/write acess to the file.

You need to pass your output file to the print function:

Code:

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      bin_print(test2_file,num,no_bits);

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Then bin_print() would be:

Code:

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bin_print(FILE *fp, int x, int n_bits)
{
  int j;

  fprintf(fp,"\nno. %d in binary: ",x);

  for( j = n_bits - 1; j >= 0; j--)
  fprintf(fp,"%i",( x >> j ) & 01);
}

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