POP-1: an on-line language

Lisp, etc.) are designed for off-line use. With the above examples in mind, certain principles seem obvious. The online user can make best use of such a system by building up complex entities in small units. For example, when calculating a large expression, it is better to work out parts of it and store these parts in variables, rather than try to do the whole thing at once. In the above examples pop-1 has appeared as a language with a fixed vocabulary.