Display

This document details "DISPLAY," a data display facility for PDP-12A computers, tailored for routines that don't require complex display processing or cannot dedicate significant core memory. It allows for the visualization of any contiguous section of core memory through a movable "window," augmented by a cursor and an octal readout of cursor positions to facilitate operator interaction.

The system requires a PDP-12A computer and specific core allocation: two PDP-8 pages in field Ø (excluding page Ø), beta registers Ø, 1, and 2, and six locations in page Ø. The binary output resides in a single tape block.

There are two primary calls to "DISPLAY":

1. Initial Call (IDORA): Configures the display by specifying the start and end 15-bit addresses of the data buffer (which must be at least 512 points long and is treated as a core ring), a 12-bit Y offset to be added to the data, and an SCR K instruction for Y-axis scaling.
2. Refresh Call (RDORA): Displays 512 points of the data buffer based on the current window and cursor settings, prepares for the next refresh, and returns control to the calling program.

Operator interaction is facilitated by:

• Knob Ø: Controls the position of the data window within the buffer (clockwise for moving right, counter-clockwise for moving left).
• Knobs 1, 5, and Sense Switch 5 (SSW 5): Control a cursor. If SSW 5 is Ø, Knob 1 moves the cursor along the displayed curve. If SSW 5 is 1, Knob 1 controls the horizontal position and Knob 5 controls the vertical position independently of the curve.

Four octal words are displayed in the top-left corner, providing information about the cursor: the 15-bit core address of the cursor point, the 12-bit contents of that memory location, and the cursor's relative Y coordinate on the scope. These values are accessible to the calling program from page Ø after a refresh. The document also outlines the internal workings of IDORA and RDORA, and details standard parameters and memory locations for the display routines.