Work started on GROATS in April 1968 when the purchase of an SC4020 was approved. The users of Atlas were approximately 80% Fortran and 20% Algol. Paul Nelson wrote SCFOR to support the Fortran users and Bob Hopgood wrote GROATS to support the Algol users.

GROATS was heavily influenced by POLYGRAPHICS which the Laboratory ported to the IBM 360/195 for IBM Fortran users.

The main novel features were:

  • The definition of regions with their own user coordinates was hierarchical. So regions could be defined within regions each with their own coordinate system.
  • The Bell Labs fonts were ported so that a set of fonts were available for textual output
  • A font definition program was implemented on the PDP15 so that non-standard fonts could be defined. In consequence there was support for Greek, Hieroglyphics etc
  • An open text font that could easily be zoomed was defined in conjunction with the BBC for the Open University Mathematics films
  • Regions could be reflected, rotated and expanded so that a variety of animation effects were possible
  • Regions could be masks that stopped drawing inside the boundary of the region
  • Shading a la Flash was available so that lines drawn could have a shadow that appeared above to the left, right or below the curve specified.
  • Right to left and left to right writing directions for text was allowed
  • Sets of drawing commands could be filed away for future use as pictures
  • Inbetweening was achieved by a function draw from to that changed one picture into another over a sequence of frames
  • Transitions were provided in the same way as SCFOR, gradually randomly eroding the lines drawn in the starting picture and replacing them with lines drawn in the second picture
  • A library of useful functions for drawing graphs etc and even 3D hidden line elimination with perspective viewing were eventually added

A full description of the system can be found in the GROATS Manual.

A Film describing the system is available on the Chilton website:

Groats Film:

A version of the original film has been created using SVG with a few changes where the original art work no longer exists:

ATLAS COMPUTER LABORATORY