GEOS SDK TechDocs
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Overview
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2 The System Architecture
GEOS is a state-of-the-art graphical operating system combining the latest software technology with numerous innovations. Its tightly coded assembly language and object-oriented system turns the humblest 8088-based PCs with as little as 512 K of RAM into graphical workstations. On higher-end machines, GEOS is in a class by itself--performance on 80286, 80386, and 80486 machines with extended or expanded memory is exceptional.
Besides being coded entirely in object-oriented assembly language (a concept and language developed by Geoworks), GEOS is built on one of the most sophisticated operating system architectures available for PCs. Most of the GEOS kernel and system is composed of dynamically-linkable libraries; in addition, developers can create their own libraries to support entire generations of applications.
GEOS also includes true pre-emptive multitasking, multiple threads of execution within single applications, built-in outline font technology, and drivers for various devices such as printers, mice, video cards, file systems, keyboards, parallel and serial ports, task switchers, power management systems, and font engines. Development for GEOS is easy and quick; much code traditionally required by applications has been provided within the system software, thereby reducing time spent by application programmers on coding and debugging.
In addition, GEOS employs a breakthrough generic user interface. Applications specify their user interface needs, and the system dynamically chooses the proper manifestation of the UI at run-time through the use of specific UI libraries. Complex drawing and geometry are handled automatically by the UI library. The generic UI allows applications to work with various UI specifications without being recompiled. Users can choose the look and feel they want without burdening the application programmer with extra coding.
Among the other advanced features included in GEOS are a single imaging model providing true WYSIWYG (a single image is used both for drawing to the screen and for printing); automatic scaling and scrolling of displayed data; dynamic memory management and virtual memory; an item database manager; a graphic object library including support for resize, move and scale operations; complex and complete text formatting and editing; specialized generic controller objects providing standard user interface and functionality; and full network support. Several other mechanisms and libraries not mentioned here are also built into the system.
The following sections of this chapter describe many of these concepts and implementations, providing a quick-view of the GEOS system as a whole. More information may be found on individual topics elsewhere in this developer's kit. This chapter provides the background information necessary, however, to take full advantage of all that GEOS has to offer the application developer.
GEOS SDK TechDocs
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| Overview
| 2 The System Architecture