Operating Systems An Introduction

2 What Does An Operating System Do? Manages the hardware and software resources of the system. In a desktop computer, these resources include such things as the processor, memory, disk space, etc. Provides a stable, consistent way for applications to deal with the hardware without having to know all the details of the hardware.

3 Operating systems Hardware Operating system User Application User The operating system acts a a ‘shell’ around the hardware. The applications software need an operating system to work, and users need the applications software to interact with the hardware via the operating system.

4 Popular Operating Systems UNIX Linux Windows 2000 Windows XP Windows 2003 Macintosh OS X

5 What Kinds Are There? Real-time operating system (RTOS) - Real-time operating systems are used to control machinery, scientific instruments and industrial systems. An RTOS typically has very little user-interface capability, and no end-user utilities. Single-user, single task - Operating system designed to manage the computer so that one user can effectively do one thing at a time. The Palm OS for Palm handheld computers is a good example of a modern single-user, single-task operating system.

6 What Kinds Are There? Single-user, multi-tasking - Type of operating system most people use on their desktop and laptop computers today. Multi-user - A multi-user operating system allows many different users to take advantage of the computer's resources simultaneously. The operating system must make sure that the requirements of the various users are balanced, and that each of the programs they are using has sufficient and separate resources

7 Networked is not Multi-user Most modern operating systems can exist in a network. A user on one computer on the network can connect to shared directory/folder on another computer. However this does not necessarily make the operating system multi-user. A user connected to a shared resource on another computer is not actually using any of that computer’s CPU or memory.

8 Networked is not Multi-user Using this yardstick UNIX/Linux is considered multi- user. When a user on another computer connects to a UNIX computer using telnet or X-Windows then that user is actually using CPU and memory resources on the UNIX computer. UNIX/Linux can also function as a networked computer when running services such as NFS or Samba.

9 Networked is not Multi-user Like UNIX, Windows can function as a networked computer. When the File and Printer Sharing Service is enabled, users on other computers on the network can connect to shared folders and printers. Users connected to those shared resources are not actually utilising the CPU or memory of the computer housing the shares.

10 Networked is not Multi-user Here are some features of Windows that may qualify it as a multi-user OS. – Windows XP has a switch user function, a second user can log onto Windows XP while leaving most of the first user’s programs running. – Windows 2000/2003 Server has a telnet server, similar to the telnet service in UNIX. – Windows 2000/2003 Server can function as a terminal services server, users connected as terminal services clients will actually be using the CPU and memory of the Windows server.

11 History of UNIX Late 1960s – UNIX designed by Ken Thomson of AT&T Bell Laboratories UNIX rewritten in the C-language by Dennis Ritchie, and distributed for a small fee to universities First commercial version, UNIX Version 6, developed by AT&T Berkeley Software Distribution (BSD) UNIX produced.

12 History of LINUX Richard Stallman releases his GNU (aka "GNU is Not Unix") Manifesto thus starting the open source revolution Andrew Tannenbaum creates MINIX, a small, highly portable Unix clone for educational/academic purposes. Sep 1991 – Linus Torvalds releases Linux version 0.01's source code. It isn’t an independent OS due to the fact that it still needs MINIX to compile.

13 History of LINUX Dec 1991 – Linux v0.11 released as a standalone operating system with floppy disk support – Slackware Linux v1.00 released by Patrick Volkerding – RedHat Linux v1.00 released – Debian Linux v1.00 released.

14 Red Hat Linux Screen Shot

15 History of Windows 1975 – Microsoft founded by Bill Gates and Paul Allen – MS-DOS v1.0 released – Windows v1.0 released as a GUI running on top of MS-DOS – Windows for Workgroups v3.11 released with integrated network capability – NT 3.1 released, MS-DOS independent.

16 History of Windows 1994 – NT 3.5 released, 32-bit processing – Windows 95 released as an upgrade to Windows – Windows 98 released – Windows 2000 released – Windows XP released, 64-bit version available – Windows Server 2003 released.

17 What is Macintosh OS X Mac OS X is a super-modern operating system that combines the power and stability of UNIX with the legendary elegance of the Macintosh. Mac OS X features a stunning new user interface called Aqua, making work and play on the Mac even more intuitive for new users, while providing powerful, customizable tools for professionals. At the foundation of Mac OS X lies an industrial- strength UNIX-based core operating system that delivers unprecedented stability and performance. Quote from

18 Macintosh OS X Screen Shot