Thanks again ahead of time.

I am looking to write a program that opens a text file, takes the text and converts all characters (excluding special and numbers) to capital letters.

I am unsure where I am going wrong for some reason I am using d, and cannot get it to code correctly keep getting char to char error. Please let me know what I have messed up as I am a little confused.

Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define MAXCHAR 250
int main(void)
{
   FILE *fp;
   char filename[MAXCHAR];
   char d;
  
   printf("Enter the name of the file to open\n");
   fgets(filename, MAXCHAR, stdin);
   filename[strlen(filename) - 1] = '\0';

   if  (!(fp = fopen(filename, "r+")))
   {
      printf("Unable to open %s\n", filename);
      exit(EXIT_FAILURE);
   }

  else
  {
       fgets(d,MAXCHAR,fp);
        if (fp > 'a' && fp < 'z')
        {
          fp = tolower(fp);
        }
        fputs(fp);
        }

   system("Pause");
   return 0;

}