Arrow keys and editing
The 
and 
move the cursor through what you typed. Right after an answer, they bring the equation back so you can fix it. The 
and 
scroll through menus and step through earlier calculations. 
removes the character at the cursor, or the last one when the cursor is at the end. And 
with 
switches between insert mode, the default, and overwrite mode. Insert mode shows a triangle cursor, overwrite mode a block cursor.