Two approaches to on-line graphics systems

This article describes two types of software systems which provide an interface to users who wish to apply the power of interactive graphics to their specific problem. The systems are based on an 8K IMLAC PDS-1 minicomputer CRT display which provides sufficient processor power to handle display generation, management, and dynamic manipulation. The minicomputer software was first designed as an independent operating system which not only provides the user with high-speed timesharing access to the host computer, but also the resources of the local processor and its associated input/output devices. In this configuration, host compiled FORTRAN IV programs are loaded into the minicomputer through the timesharing link and executed independently from the host processor. A higher degree of processing is provided by the master-slave relationship between a local DEC PDP $\text{11}\text{40}$ minicomputer and the IMLAC. The user's FORTRAN IV program, executing in the PDP $\text{11}\text{40}$, directs an IMLAC graphics subsystem through subroutine calls. These systems provide the programmer with a foundation for a broad range of high level applications involving computer graphics.