EXOS 2.1 Kernel Specification

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1. Introduction.

EXOS is the extendable operating system for the micro­computer. It provides an interface between an applications program (such as the IS­BASIC interpreter) and the hardware of the machine. The main features of EXOS are a channel based input/output system and sophisticated memory management facilities. The I/O system allows device­independent communication with a range of built in devices and also any additional device drivers provided by the user.

The built­in devices included with the EXOS kernel in the ROM, are:

• Video driver providing text and graphics handling.
• Keyboard handler providing joystick, autorepeat and programmable function keys.
• Screen editor with word processing capabilities.
• Comprehensive four source stereo sound generator.
• Cassette tape file handler.
• Centronics compatible parallel interface.
• RS232 type serial interface.
• Intelligent Net three wire network interface.

This document describes the EXOS kernel, wich interfaces between an applications program and the various devices, providing memory management and various other facilities. It explains the action of the kernel from the point of view of both devices and applications programs. The built­in device drivers themselves are each described in separate documents, some of wich make reference to the kernel specification.

It is intended that, along with the various device driver specifications, this document will provide sufficient information for writing applications programs using EXOS, or for writing new EXOS device drivers. All details in this document apply to EXOS version 2.1.

Next chapter: Overview of the EXOS Environment