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:

#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);
}

man fprintf, fscanf, fgets

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

Originally Posted by Guti14

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

Code:

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

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

Code:

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

to have both read/write acess to the file.

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

Code:

      bin_print(test2_file,num,no_bits);

Then bin_print() would be:

Code:

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);
}