Two of the four are simply the standard ASCII control characters: · Control-H is Back Space: it moves the cursor one position left. · Control-J is Line Feed:

Two of the four are simply the standard ASCII control characters: · Control-H is Back Space: it moves the cursor one position left. · Control-J is Line Feed: it moves the cursor one line down. The other two seem to be arbitrary on the part of the ADM-3A designers, and having Control-L (Form Feed) perform cursor-right rather than clear-screen seems a bit dubious, but given their constraints and the desire to keep all the motions together, it's hard to argue for any different choices.