⍫ Lock

You can lock a user-defined function, operator or method by entering or leaving the line editor using the 'del-tilde' character (⍫) rather than 'del' (∇).

Once a function has been locked, it can be run, but cannot be edited or displayed. If you try to edit it, a DEFN ERROR will be reported.

If execution of a locked function is stopped because of an error or interrupt, the function is never suspended, but instead is abandoned. Any error within a locked function will cause a DOMAIN ERROR to be signalled to the caller.