POS is the graphical interface to QSIM. It provides a set of primitive plotting functions which are used to display the results of a simulation. Currently it runs under the Symbolics, Explorers and X-Windows. xPOS is the latest version of POS. This section is designed to provide a description of the modifications made to POS so that it is compatible with X-windows. For more information about POS, please refer to the POS User's Manual.
The interface between POS and X-windows occurs via a C program. The POS code places information about the plots to be drawn in a temporary file. This file is then read by the C program which interfaces with X-windows and creates the desired window. The interface between C and X-windows is a stable interface which is well documented. Conversely, the Lisp interface to X-windows (CLX) is less-stable and poorly documented. Use of a C program for this interface should simplify maintenance and reduce the system dependencies.