A Patch to Focal-W to Use the Linc-8 Display

This document details a software patch for FOCAL-W (version 8/68) designed to enable the use of the LINC-8 point display for users of the LINC-8 computer system.

Key aspects of the patch include:

• Functionality: It allows users to set up and intensify X and Y coordinates similarly to the standard PDP-8 display.
• Coordinate Changes: X and Y coordinates must be reversed in the code (e.g., SET H = FDXS(Y)+FDIS(X)).
• Coordinate Ranges: The X-axis range is 0 to 512, and the Y-axis range is -256 to +256.
• Limitations: Applying this patch disables the ARCTAN function in FOCAL. If ARCTAN is required, it must be calculated using the FEXP function.
• Implementation: The document provides specific memory location modifications and assembly source code required to implement the patch into FOCAL-W.