Overview of the University of Pennsylvania CORE System Standard Graphics Package Implementation
The CORE System is a proposed standard for a device-independent graphics system. The concept of a device-independent system was first developed in 1977 by the Graphics Standards Planning Committee (GSPC) of ACM Siggraph and later refined in 1979 [1,2]. The CORE System design has received favorable reviews and has been implemented by various vendors at several universities, and other computing facilities (e.g. [3,7]). The main objectives of the CORE System are to provide uniformity, compatibility, and flexibility in graphics software. Three advantages that the CORE system provides over non-standard graphics systems are device independence, program portability, and functional completeness. A large number of different graphics hardware devices currently exist with a wide range of available functions. The CORE System provides device independence by shielding the applications programmer from specific hardware characteristics. The shielding is at the functional level: the device-independent (DI) system uses internal routines to convert the application programmer's functional commands to specific commands for the selected hardware device driver (DD). The progammer describes a graphical world to the CORE System in device-independent normalized device coordinates. The programmer also specifies the viewport on the logical view surface (output device) where a picture segment is to be placed. As the CORE System becomes the accepted standard graphics package, program portability will become more feasible. Program portability means the ability to transport application programs between two sites without requiring structural modifications. The CORE System was designed for functional completeness so that any graphics function a programmer desires is either included within the system or can be easily built on top of CORE System routines.