What is an operating system?

• An OS is a program that acts an intermediary between the user of a computer and computer hardware.

• A program that runs on the “raw” hardware and supports

             –Resource Abstraction (across different types of hardware)
             –Resource Sharing

• Manages the hardware resources

             –Each program gets time with the resource
             –Each program gets space on the resource

Modern Operating Systems

• Mainframe operating systems: MVS (Multiple Virtual Storage)
• Multiprocessor operating systems: Cellular IRIX
• Server operating systems: FreeBSD, Solaris
• Personal computer operating systems: Windows, Unix, Linux
• Real-time operating systems: VxWorks
• Embedded operating systems: Inferno, Cisco IOS

Goals of an Operating System

• Simplify the execution of user programs and make solving user problems easier.
• Use computer hardware efficiently.
• Allow sharing of hardware and software resources.
• Make application software portable and versatile.
• Provide isolation, security and protection among user programs.
• Improve overall system reliability

Why should we know about Operating Systems?

• Need to understand interaction between the hardware and applications
• New applications, new hardware..
• Need to understand basic principles in the design of computer systems
• efficient resource management, security, flexibility
• Increasing need for specialized operating systems
• e.g. embedded operating systems for devices -cell phones, sensors and controllers
• real-time operating systems -aircraft control, multimedia services

Embedded Operating Systems

The zoo of Operating Systems

• Windows 98 Second Edition
• Windows Millennium Edition
• Windows 2000 Server with SP4
• Windows XP Professional with SP2
• Windows 2003 Server with SP1 or SP2 or R2
• Windows Vista
• Windows 7
• Red Hat Enterprise Linux 3/4
• Fedora Core Linux
• Sun Solaris

The zoo of Application Software

• MS Office 2000/XP/2003/2007
• Open Office
• Database Servers like Oracle10g, MS SQL Server 2005
• Content Management Systems like PostNuke, PHPNuke
• Encrypting Software like Truecrypt, Cryptainer
• Shredder Software like Eraser
• Antivirus Software like Symantec-Norton AV, McAfee, ClamAV, Kaspersky, Trend Micro
• Multimedia Software like WinAmp, Media Player
• Office Automation tools like Schedulers, Calendars, Mailers
• Web Browsers like IE, Opera, FireFox, Netscape
• Personal Fire Walls like ZoneAlarm