Operating Systems

Chapter 3c

Operating System

Functions of Operating Systems

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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

Types of Operating Systems

• 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

Types of Operating Systems

• 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

Types of Operating Systems

• 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

Multi user/Multi tasking OS

Providing a User Interface

• User interface

– How a user interacts with a computer

– Require different skill sets

Providing a User Interface

• 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

Graphical User Interface

Providing a User Interface

• Command line interfaces

– Older interface

• DOS, Linux, UNIX

– User types commands at a prompt

– User must remember all commands

– Included in all GUIs

Command Line Interface

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

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