When i first started programming in Basic on a PDP11 i wrote a program with a password embedded in it but it included deletion of the characters and typing over them with hashes as part of the password.

If you listed the program on the terminal it printed, deleted and printed hashes fast enough you could not read it, and if you printed out to the printer, it printed fast enough you could not read it and hashed out well enough you could not read it either..