DMCL is an abbreviation and stands for Defined Macro Command Line. It is meant to be an extension to the current BAE keyboard input system, where the user can redefine single keypresses such that a special ULC function is called.
DMCL tries to provide fast access to the most used functions of the SCM and GED module for all people that like to type in commands, instead of clicking their way through menus with the mouse.
It is based on short command words with 2-4 letters, so called mnemonics. They build an orthogonal set of commands, consisting of a prefix and suffix. The prefix equals the action that should be executed, while the suffix specifies the object that is about to be changed. For example, in order to add another part/symbol you type the command "as" (Add Symbol). If you want to delete the same object again, simply replace the "a" for "Add" with a "d" meaning "Delete". So the correct command would be "ds" (Delete Symbol) in the latter case.
This way you are able to access the most often used functions like add/move/copy in a consistent way for all objects that can be created or moved around. With this you have functions like "cs" (Copy Symbol) at your fingertips, that are deeply buried in the standard menus otherwise.