Brian Katzung's Early Computing Environment


Back To Hobbies 

Early Computing 

Here is a picture of the "Pharmacology Graphics System" in its incarnation as a Digital Equipment Corporation (DEC) PDP 11/34. (It began its life as a PDP 11/10 with a full complement of 56 kilobytes!) At the left is the dot matrix printer, the vector-drawing graphics display with "light pen", and, on the shelf next to the tractor feed of the printer, a pen plotter (a one-color-at-a-time precursor to the ink jet). On the right are two dual disk drives, each containing one permanent and one removable "RK05" platter (only about a megabyte or two capacity per platter!), the analog-to-digital and digital-to-analog converter patch panel (for data acquisition and control), the central processor, and a storage bay for removable RK05 platters. 

Vector-drawing displays move their electron beam in an arbitrary path called a display list. The refresh rate is a function of the length of the display list, so the display starts to flicker badly if the display list becomes too complex. The "light pen" reports the X and Y coordinates of the electron beam as it passes by the photodiode at the tip of the light pen. Instead of moving a cursor with a mouse and clicking mouse buttons, you drag a "target" around the screen and point at options listed on the screen with the light pen. 

Early incarnations of the system ran DEC's RT-11 real-time operating system. Custom applications were written BASIC and Fortran IV. Later incarnations ran small flavors of BSD UNIX. We wrote UNIX device drivers for the graphics display and the A/D and D/A converter and ported the custom applications to C.

Home * Top * Back
Updated 11 September 1998