The Units package allows you to represent, convert, and perform arithmetic with physical unit values (e.g. distances, velocities, accelerations, etc). There is not much formal documentation, but most of the classes in this package have comments. The most important methods are those in Unit and UnitValue. You should look through all those. To add your own units, see the classes BaseUnit, DerivedUnit, NamedUnit, and PrefixedUnit, and look through the initialization code. You should duplicate what is done there to add your own units. Remember to send Unit initialize to make your changes take effect. Note that you can send Unit printAbbreviated: true or Unit printAbbreviated: false to control how units print. Ported to Squeak by Helge Horch