Theme: A sort of remake of the famous Ed text editor with undo and redo, with the following commands:
- ind1, ind2c: change the text to the lines between ind1 and ind2, there will be ind2-ind1+1 lines plus a line with a single dot
- ind1, ind2d: deletes the lines between ind1 and ind2 (extremes included)
- ind1, ind2p: print the lines between ind1 and ind2
- nu: undo the last n commands (c or d)
- nr: redo the last n commands undone with undo
- q: ends