7-segment LED Displays can display a limited number of alpha characters - 'E' being one of them. The problem is when you want to display characters that contain diagonals like 'K' or 'M' or 'Z', and then you need a 'starburst' LED display, but unfortunately you then also need to drive far more segements.

There usually isn't a segment 'H' on 7-segment LED's unless you're counting the Decimal Point that's normally found on them.