ICT(ID:7347/ict002)

Satellite graphics language 

for Interactive Control Tables

Cotton and Greatorex, developed for the UNIVAC 1557

Specially built lowe-level interpretive language to communicate with and receive graphics back from, satellites
References:
  • Cotton, I. W., and F. S. Greatorex, "Data Structures and Techniques for Remote Computer Graphics" pp553-544 view details
          in [AFIPS] Proceedings of the 1968 Fall Joint Computer Conference FJCC 33 view details
  • Cotton, I .W., "Languages for Graphic Attention Handling" view details
          in Proc. Computer Graphics Symposium, Brunel University 1970 view details
  • Foley, James D. "The Design of Satellite Graphics Systems" view details Extract: ICT
    Cotton and Greatorex describe a system for UNIVAC 1557 (graphics support CPU) and 1558 (DPU) linked to a UNIVAC 1108 (main CPU). The main application program is written in FORTRAN, and subroutine calls are used to build a hierarchical data structure. At any time the structure can be clipped, and a distillate transmitted to the satellite. The same hierarchical structure is maintained by the satellite. The satellite can do additional clipping, and can create a DPU program.

    The satellite is accessable to the application programmer via an interpretive language whose syntax is similar to assembler language, but with more powerful semantics. It is called ICT (for Interactive Control Tables). The language operates on 65 registers plus a stack holding a maximum of 15 entries. Some registers have permanently assigned meanings: for instance, registers 8 and 9 always contain the tracking cross's current position.
    The language is capable of providing user feedback and interaction of any sort, including but not limited to rubber-banding, intensification of detected entities, prompts, and constrained line drawing. It can interrogate and modify the satellite's hierarchical data structure, can perform logical and arithmetical computations, can compose messages to be transmitted to the main CPU, and can effect transfers of control and subroutine invocations. Hence the language is powerful. A large number of pictures changes can be made without main CPU intervention.
    When messages are sent to the main CPU, the application program decodes them, and either updates the data base as required, or performs some analysis of the data base. In the former case the user can continue his interactions, as the satellite's data base has already been updated. In the latter case he will normally wait for the results before proceeding.
    The UNIVAC system has many advantages. A lot of work can be done by the satellite, so the user can receive fast response to most of his actions. Communication link traffic can be
    low. There is some flexibility in dividing processing between the two computers, although semantic analysis must be done by the host. But the programmer must be bilingual, so there are learning difficulties. The syntax of the interpretive language could easily be considerably improved at rather low cost, thereby reducing some of the learning problems. Finally, the programmer is forced to be very conscious of the dual CPU configuration.

          in Klinger, A.; Fu, K. S.; Kunii, T. L. "Data Structures, Computer Graphics, and Pattern Recognition" (Largely based on IEEE Computer Society conference held in Los Angeles, May 1975) Academic Press, NY 1977 view details