VB10C Interactive Graphics Terminal Jul70

This document describes the VB10/C Interactive Graphics Terminal, developed by Digital Equipment Corporation in July 1970, and its associated software and a graphical input device.

Key aspects of the VB10/C Terminal and its Software:

1. Purpose: It is a highly interactive display system for the PDP-10, designed for user freedom and flexibility under time-sharing.
2. Hardware: Consists of a 340/C display directly connected to PDP-10 memory. Features include memory protection, relocation, slave mode, raster mode, and subroutining. User interaction is facilitated by a standard Light Pen, with optional Function Box and Tablet.
3. Software Package: A crucial component, developed by Harry R. Lewis at NIH, allows users to write display programs in high-level languages like FORTRAN or LISP, abstracting away hardware instructions.
   • Capabilities: Includes routines for displaying vectors, points, and text; controlling scale and intensity; defining custom number spaces and viewpoints; generating pictures, subpictures, and nested subpictures; clipping (not displaying content outside defined windows); blanking/unblanking pictures; and managing memory.
   • Three-Dimensional Graphics: Supports creation and manipulation of 3D pictures, including rotation (pitch, yaw, roll) and zooming, by adjusting transformation coefficients.
   • Special Routines (FORTRAN): Provides specific routines for raster mode display and comprehensive three-dimensional display, including translation, rotation, and perspective projection using a 4x4 homogeneous matrix.
4. User Interaction: Supports various input methods from simple function box/teletype inputs to precise graphical data input via the Tablet (e.g., for drawing new structures or circuit design).
5. Document Structure: The manual details initialization procedures (FORTRAN and LISP), setting windows and viewports, methods for picture generation, plotting primitives (points, vectors), text display, light pen usage, miscellaneous picture handling (blanking, subpictures, replacement), and error messages.

The Grafacon (Rand Tablet) Service Routine (separate section):

The document also provides a detailed description of the Grafacon (Rand Tablet), a graphical stylus input device:

1. Hardware: A 10"x10" grid with 1024x1024 wires, offering 2^20 distinguishable positions. The stylus has a microswitch to detect pen-down events. Its coordinate system aligns with the DEC 340 display.
2. Functionality: Senses stylus position and converts it into coordinates. Samples data at regular intervals (~220 microseconds) and can generate interrupts for new data or pen switch changes.
3. Data Modes: Supports "Image Mode" (raw data) and "Image Binary Mode" (filtered, stripped to X/Y coordinates).
4. Data Spacing: Allows users to specify data sampling rate (equal-time) or thin data based on spatial distance (equal-space).
5. Interactive Features:
   • Tracking: Allows the Grafacon to modify a user's display file in real-time by placing coordinate data at a specified "tracking address," analogous to light-pen tracking.
   • Inking: A display subroutine that shows the pen's trajectory on the tablet when the pen is down, using an "ink buffer."
6. Control: The USETO UUO (User Unimplemented Operation) is used to pass parameters for configuring inking, tracking, data rate, and uptime.

In summary, this document is a comprehensive guide to the VB10/C interactive graphics system, detailing its hardware, its powerful high-level software for graphics programming, and the integrated use of the Grafacon graphical input tablet.