$Plot

This document serves as the user manual for $PLOT, a FOCAL-12 overlay designed for the PDP-12 computer. The program allows users to operate an incremental digital plotter directly from FOCAL programs. It provides two main functional capabilities via "extra functions":

• FX: Handles drawing lines and points, with support for defined coordinate ranges (-2047 to +2047) and pen control (up/down).
• FZ: Facilitates drawing text characters by utilizing the pen motion table stored in a separate file, $CHAR.

The manual includes technical details such as loading procedures, calling sequences for various drawing commands, character rotation methods, system requirements (8K core and a linctape), and instructions for modifying the program for non-standard plotter interfaces. It also identifies specific error messages and potential limitations regarding buffer handling.