IMPLEMENTATION OF GRAPHICAL KERNEL SYSTEM LEVEL--Ob ON IBM-PC-AT COMPATIBLE

Abstract

With the proliferation of sophisticated and inexpensive graphic devices, a need for an international standard was felt. The Graphical Kernel System (GKS), evolved after years of research and deliberations, emerged as a conerstone of a family of compatible graphic standards. GKS standard defines a two dimensional (2D) system capable of performing tasks relating to picture generation and presentation, structuring of pictures, handling of input from workstations, controlling the workstations attached to the system, long time storage of graphical data and thus can be used in diverse applications. Utilising the concepts of abstract device space (called the normalised device coordinates in GKS parlance) and workstation GKS enables the development of device independent application software resulting in easy portability onto different installations. GKS is a system nucleus which defines functions without reference to specific graphical device. In addition, it is possible to tailor GKS to special qualities of specific environments using the concept of levels which define implementable subsystems leading to the development of compact yet robust graphic software. In this thesis, an endeavour has been made to implement level Ob(GKS)with the facility of picture structuring (part of level la) integrated into the system on an IBM-PC-AT iv compatible with a Colour Graphic Adapter (CGA). Five output primitives and the various attributes associated with each primitive have been implemented using the bundle concept for late binding of attributes in the viewing pipeline. A dynamically resetable normalisation transformation and workstation transformation can be defined by the user. Facility for input by way of LOCATOR logical input device with a tracking cross has been provided for interactive manipulation of structured pictures. A Workstation Dependent Segment Storage (WDSS) facility has also been provided as part of the implementation. 'C' has been used to bind the abstract data types and functions of GKS.