DX-1 Sys

The Digigraphic Display Program (DDP) is an early interactive graphics software system, developed by Charles W. Adams Associates in conjunction with Itek Corporation, for the DX-1 computer system (based on a PDP-1 computer) in 1963.

Its primary function is to enable users to create, display, and manipulate graphic and alphanumeric information such as charts, diagrams, and curves directly on a buffered display scope without flicker. The system utilizes a light pen, a push-button control panel, and foot pedals for interactive input, as well as on-screen "light buttons" for numerical input and control.

Drawings are stored in a condensed digital format called an "Entity Table," where each component (e.g., points, lines, circles, curves, polygons, dimensions, and textual remarks) is considered an "entity" and can be assigned to a "group" for collective manipulation. DDP offers features to accelerate drafting, including:

• Drawing: Sketching points, lines (with horizontal, vertical, or protractor constraints), circles, arcs, freehand curves (which can be smoothed into third-degree curves), and regular polygons.
• Manipulation: Moving, rotating, or reflecting subdrawings or copies of entities.
• Dimensioning & Query: Querying distances and angles, and generating drawn dimensions.
• Viewing & Control: Tools for scaling, magnification (zooming), and temporary or permanent erasure of entities based on type or group.
• Alphanumeric Input: Adding textual remarks with formatting options.

The program's design emphasizes extensibility, allowing for the addition of special-purpose software routines and expansion of the entity format with minimal modification.