It's actually somewhat of a challenge to display "Mem cleared" without access to the lowercase font. You have access to any uppercase character, spaces, and BASIC functions. With stat vars, you also get lowercase "a" "b" "c" "d" "e" and "r". And you can display text at a specific row and column.

I ended up displaying "M" "e" "min(" "c" "log(" "e" "a" "r" "e" "d". Then covered up the "in(" with spaces.

Then you lower your contrast for the full effect.