1. UNIX Unbounded 5th Edition Amir Afzal Chapter 2 The UNIX Operating System
Copyright ©2008 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

2. Chapter 2 The UNIX Operating System
This chapter briefly describes the history of the UNIX operating system. It explores UNIX development over the years, discusses the major UNIX versions, and explains some of the system’s important features.

3. 2.1 A BRIEF HISTORY
The UNIX operating system was the brainchild of Ken Thompson and Dennis Ritchie
Universities and colleges have played an important role in the popularity of the UNIX operating system
There are two major versions of the UNIX operating system
- AT&T UNIX version V
- Berkeley UNIX
Other UNIX varieties are based on one of these two versions
About 95 percent of the UNIX operating system is written in C.
A very small part of UNIX is still written in assembly language;
that part is mostly concentrated in the kernel, the part that interacts directly with the hardware.

4. 2.2 Other Unix Systems Linux Solaris UnixWare X Window System
X Window system, also referred to as X or X11, is not a UNIX version.
It is a graphical user interface designed to provide the bases for graphical windowing in a way that is portable to most UNIX platforms.

5. 2.3: OVERVIEW OF THE UNIX OPERATING SYSTEM
The UNIX operating system is implemented in a layered-style software model
Kernel
The UNIX kernel, also called the base operating system, is the layer that manages all the hardware-dependent functions
Resident Modules Layer
Provides service routines that perform user-requested service
Utility Layer
It is the UNIX user interface, commonly referred to as the shell

6. Figure 2-1: The Unix System Components

7. 2.4 UNIX FEATURES Portability Multiuser capability
Multitasking capability
Hierarchical File System
Device-Independent Input and Output Operations
User Interface: Shell
Shell Script

8. Utilities
The UNIX system includes more than 100 utility programs, also called commands
Utilities are part of the standard UNIX system and are designed to perform a variety of functions required by the users
These utilities include the following:
• Text editing and text formatting utilities
• File manipulation utilities
• Electronic mail ( ) utilities
• Programmers’ tools

9. System Services
The UNIX system provides a number of services that facilitate administration and maintenance of the system.
The following are some of these services:
• System administration service
• System reconfiguration service
• File system maintenance service
• File transfer service (called UUCP for UNIX to UNIX Copy)