Abstract: A command language system is disclosed wherein memory stacks register specific definitions for generic names, which definitions are appropriately selected in timely response to a name, on the basis of stack arrangement. A structure is included for searching the stack in order and detecting the first definition for a name of current interest. Thus, the stack is used to define the order of the name searching. As a consequence, in the interpretation of command languages, the user is given control over the context in which the names are executed. Specifically, a command program wil behave according to the definitions of the commands in a current context. The system further includes structure for deleting definitions from the stack which have been used and for sensing the bottom of the stack as a function of control.