When you type commands, text jumps around on the screen and
nothing works the way it's supposed to.
You may have hit the
key without noticing it.
is case-sensitive. That is, uppercase commands (
, etc.) are different from lowercase commands
), so all your commands are being
interpreted not as lowercase but as uppercase commands.
key again to return to lowercase, then type either
to restore the
last line changed or
to undo the last command.
You'll probably also have to do some additional editing to fully
restore the garbled part of your file.