GNU Compiling Question

I have this program that compiles and runs in microsoft C++ but when I try to compile with GNU either no output is produced or the output file is put somewhere and I don't know where it is! I am using the gcc command to compile. Should that put the output file in the same directory as my .c file? Or is my problem of a different nature?

First off, thank you very much for the help!
There is an fprintf in the .c file. So it should be printing to that file right? Also, if I open the a.out file there's a bunch of unreadable stuff in the file.

Code:

#include <stdio.h>
#define max 5000

int main (void)
{

     char data [max];
     int j = 0, i=0;
     FILE* input;
     FILE* output;


     input = fopen ("input_40x10x300_nohead.cor", "r");   //open the input file
     output = fopen ("input_new_40x10x300.cor", "w");

         for(j=1; j<max && fscanf(input, "%c", &data[j]) != EOF; j++)
         {

                                if (data[j] == ' ')
                {
                    i++;
                                }

                                if(i < 4  || i >= 7)
 {
                  fputc (data[j], output);
                 }

                                if (data[j] == '\n')
                                {
                                         j=0;
                                         i=0;
                                }

     }

         fclose (input);
         fclose(output); 

     return 0;
}

Also, previously this:

Code:

 fprintf (output, "%c", data[j]);

was in the place of:

Code:

 fputc (data[j], output);

but that did not work either.

I added the code above. I am not familiar with perror but I assume that if that condition was true it would have reported that error during compiling. The program compiled fine and when I added fprintf (output, "Outside") and another one that should print "inside" in the loop just to see if I could write to the file at all. This did not print to the file either. This leads me to believe I have some error in opening the file or in my syntax in writing to the file. Thanks again for the help, it is very appreciated.

The code again, for reference:

Code:

#include <stdio.h>
#define max 5000

int main (void)
{

     char data [max];
     int j = 0, i=0;
     FILE* input;
     FILE* output;


     input = fopen ("input_40x10x300_nohead.cor", "r");   //open the input file
     output = fopen ("input_new_40x10x300.cor", "w");

        if ( input == NULL ) {
    perror( "Can't open input file" );
    exit( 1 );
}

        fprintf (output, "outside");
         for(j=1; j<max && fscanf(input, "%c", &data[j]) != EOF; j++)
         {


                                if (data[j] == ' ')
                {
                    i++;
                                }

                                if(i < 4  || i >= 7)
 {
                   fprintf (output, "%c", data[j]);
                   fprintf (output, "inside");
        }

                                if (data[j] == '\n')
                                {
                                         j=0;
                                         i=0;
                                }

     }

         fclose (input);
         fclose(output);

     return 0;

*edit: code was only half there.