Statement C Tutorial

#include 
#include 
main()
{
  char cResponse = '\0';
  printf("\nPlease enter a letter: ");
  scanf("%c", &cResponse);
  if ( isdigit(cResponse)== 0 )
    printf("\nThank you\n");
  else
    printf("\nYou did not enter a letter\n");
}
Please enter a letter: 1

You did not enter a letter