Thread: Testing a binary file related program // Need help

Hi everyone! The following program has the purpose of writing in a binary file 65536 combinations of binary numbers with 16 digits. Furthermore, it also has to read from said file, given a certain combination in the line of commands, in which exact "line" is that combination located. For example, if you input "0000000000000111", it will print, "line 7". Just one more thing, i wrote two methods of finding the line, in which the first one does this without reading the file, whereas the second one is there to make sure it went to the right line, by reading the file.
With that said, i'm having two major problems:
1- The first one being that whenever i type "1111111111111111", the first process prints out line 65535. However the second one, using the fseek and fread functions prints 0... How can i fix this?
2-Can someone tell me why is it that the binary file has around 130 kb of data?
Thank you very much for the help, and as always if there is still some testing that needs to be done to make sure everything goes smoothly, please let me know!
Here's the code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>


int main(int argc, char **argv)
{
  unsigned short int w, i = 0;
  int c, b,p;
   // int a;
    FILE *f1;


    if(argc == 1)
      {
    printf("Input a certain configuration in the line of commands!\n");
    return 1;
      }


    f1 = fopen("Strings.bin", "wb+");




    for( i = 0; i < pow(2,16)-1; ++i)
      {
    fwrite(&i , sizeof(unsigned short int) , 1 , f1);
      }


    c = 0;
    i = 0;


     while (i < 16)
      {
          if(argv[1][15-i] == '1')
                c += pow(2,i);
          ++i;
      }


    printf("The given input is located in the line: %d.\n", c);


    fseek(f1,c*sizeof(unsigned short int),SEEK_SET);
    fread(&w,sizeof(unsigned short int),1,f1);


    printf("Confirmation: %d\n",w);


    fclose(f1);
       return 0;
}

Right, yeah that makes sense. But how can i fix this, i went to check my file, and well, it contains around 128 kb of data... how come?

I understood the fact that my file should be around 130 kb, but if i'm writing 65536 values, being each 2 bytes, shouldn't my file be exactly 2 x 65536 bytes as opposed to 128 kb? Or is that related to the inefficiency associated with the calculations of the powers of 2?
Just one final thing, being that i should have around 130 kb, how can i change the code for it to contain the last entry?
Thanks in advance for the help!

Originally Posted by user_0x

I understood the fact that my file should be around 130 kb, but if i'm writing 65536 values, being each 2 bytes, shouldn't my file be exactly 2 x 65536 bytes as opposed to 128 kb?

2**16 * 2 = 65536 * 2 = 131072 = 131.072kb = exactly 128 kib (where a kib is 2**10 = 1024)