Emacs is a widely used software program for—among other things—editing text documents (including this book!). Here’s a mildly simplified description of Emacs (to make this problem more manageable). In...

Emacs is a widely used software program for—among other things—editing text documents (including this book!). Here’s a mildly simplified description of Emacs (to make this problem more manageable). In Emacs, a command character is produced by pressing a letter key while holding down either the Control key, the Meta key, or both. (For example, Control+Y or Meta+B or Control+Meta+U are command characters.)

 How many command characters are there in Emacs?