A student oriented CAD system in APL

Abstract

This paper describes a two-dimensional computer-aided design tutorial system (CADETS) modelled after Unigraphics I. Written in APL, a 3279 colour graphics terminal is used as a graphics input as well as output device. The screen is divided into five windows. The main, and the largest, window is used for graphics; the others are used for user communication. Menus are used extensively to generate, modify and manipulate the display. Within CADETS, there are currently eleven ways to create a point, thirteen ways to create a line segment, ten ways to specify a circular arc, several functions to generate common geometric objects such as triangles, rectangles, polygons, conics and ten fonts to write labels. Once created, the user may pick the geometric entities in the current model for inquiry, transformation or deletion through a series of selection menus. Manipulation of geometric entities is facilitated by transformation functions such as translation, scaling, rotation, and mirroring. Options to move, copy or duplicate the transformed entities are available. Geometric models created by the user may be stored as either TSIO or VSPC data sets. The user may retrieve, inquire or change the data set names of the models at will. The power of CADETS is further enhanced by the introduction of layers. This facility enables the user to view and draw each individual layer independently or to view selected layers simultaneously. The system has been used by several users including high school students who were unaware of even the existence of APL. The system requires minimal investment on hardware as well as software compared to sophisticated expensive systems, yet provides tools for teaching several fundamental CAD techniques.