# Welcome to OS-9!

At the heart of your computer is an amazing device: the 6809 central processing unit (CPU). When introduced in 1980, This microprocessor offered sophisticated features that were only found only on much larger and costly computers. Even today, it is architecture is considered feature-rich. The OS-9 operating system was designed around the 6809 microprocessor to provide an extremely efficient and powerful operating system.

The foundation of a computer's software system is its Operating System or “OS”. It is the master control program that interfaces all other software to the system's hardware. Some of the things it must do are performing input and output operations, coordinating memory use, and many other “housekeeping” functions. All other software - programming languages, applications programs, etc. - live in your computer's memory along with the OS and depend on it to communicate with you using the keyboard and display and to store and retrieve data on disks, etc. Because virtually all other software relies on the OS, your computer's performance depends on the capabilities and efficiency of its OS.

OS-9's overall structure was based on the famous UNIX[1] operating system, which has been widely acclaimed as the operating system of the future because of its versatility, logical structure, and friendly user commands. The OS-9 family of advanced software is not only more powerful than most other microcomputer scftware - it is also much easier to learn and use.

Some of the advanced OS-9 features you'll learn about in this book are:

1. Friendly UNIX-like user interface and environment

2. Multiuser/Multitasking Real-Time Operating System

3. Extensive support for structured, modular programming

4. Device-independent interrupt-driven input/output system

5. Multi-level directory file system

6. Fast Random-Access File System

7. Readily Expandable and Adaptable Design

If you don't know what some of these thing mean yet - don't worry. As you explore OS-9 you'll soon learn how they enhance the capability of your computer and make it so much easier to use in almost any application.

OS-9 has many commands and functions - definitely more than you can learn in an evening! The best way to become an OS-9 expert is to study this manual carefully, section-by-section, taking time to try out each command or function. Because many functions affect others, you'll find this manual extensively cross-referenced so you can skip ahead to help you understand a new topic. Taking the time to study this book will certainly increase your knowledge and enjoyment of OS-9.

But if you can't wait, at least read the rest of this chapter, scan the command descriptions in a later chapter, and have fun experimenting!

[1] UNIX is an operating system designed by Bell Telephone Laboratories, which is becoming widely recognized as a standard for mini and micro operating systems because of its versatility and elegant structure.