IT_Chapter_7A

Functions of Operating Systems

• Provide a user interface

• Run programs

• Manage hardware devices

• Organized file storage

Types of Operating Systems

• Real-time operating system

– Very fast small OS

– Built into a device

– Respond quickly to user input

– MP3 players, Medical devices

• Single user/Single tasking OS

– One user works on the system

– Performs one task at a time

– MS-DOS and Palm OS

– Take up little space on disk

– Run on inexpensive computers

• Single user/Multitasking OS

– User performs many tasks at once

– Most common form of OS

– Windows XP and OS X

– Require expensive computers

– Tend to be complex

• Multi user/Multitasking OS

– Many users connect to one computer

– Each user has a unique session

– UNIX, Linux, and VMS

– Maintenance can be easy

– Requires a powerful computer

Providing a User Interface

• User interface

– How a user interacts with a computer

– Require different skill sets

• Graphical user interface (GUI)

– Most common interface

• Windows, OS X, Gnome, KDE

– Uses a mouse to control objects

– Uses a desktop metaphor

– Shortcuts open programs or documents

– Open documents have additional objects

– Task switching

– Dialog boxes allow directed input

• Command line interfaces

– Older interface

• DOS, Linux, UNIX

– User types commands at a prompt

– User must remember all commands

– Included in all GUIs

Running Programs

• Many different applications supported

• System call

– Provides consistent access to OS features

• Share information between programs

– Copy and paste

– Object Linking and Embedding

Managing Hardware

• Programs need to access hardware

• Interrupts

– CPU is stopped

– Hardware device is accessed

• Device drivers control the hardware

Organizing Files and Folders

• Organized storage

• Long file names

• Folders can be created and nested

• All storage devices work consistently

Enhancing an OS

• Utilities

– Provide services not included with OS

– Goes beyond the four functions

– Firewall, anti-virus and compression

– Prices vary

• Backup software

– Archives files onto removable media

– Ensures data integrity

– Most OS include a backup package

– Many third party packages exist

• Anti-virus software

– Crucial utility

– Finds, blocks and removes viruses

– Must be updated regularly

– McAfee and Norton Anti-Virus

• Firewall

– Crucial utility

– Protects your computer from intruders

– Makes computer invisible to hackers

– Zone Labs is a home firewall

– Cisco sells hardware firewalls

• Intrusion detection

– Often part of a firewall package

– Announces attempts to breach security

– Snort is a Linux based package

• Screen savers

– Crucial utility for command line systems

• Prevents burn in

– Merely fun for GUI systems

– Screen saver decorates idle screens