ConvertToUppercase

#include <stdio.h>
#include <string.h>
char * ConvertToUppercase(char * input)
{
    char output[255];
    int i;
    for(i=0;i<strlen(input);i++)
    {
        output[i] = input[i]-32;
    }
    return output;
}
main() {


   FILE *fp;
   char buff[255];

   fp = fopen("test.txt", "r");


   fgets(buff, 255, (FILE*)fp);
   printf("3: %s\n", buff );
   fclose(fp);
   printf("%s",ConvertToUppercase(buff));
}