which were performed immediately, or to prefix them with a line number, in which case they were added to the program if they were unique, or overrode existing code if the same number had previously been used.

The method of operation is similar to BASIC's "immediate mode" vs. "program mode". It contrasts with JOSS, in which all commands, both program and direct, were saved and loaded as part of the user's workspace. This allowed JOSS to have commands without line numbers, which they used for definitions