Computers
Software
Computer Layers
Hardware
BIOS
Operating System
Applications
Software Classifications
System Software (operating system)
 Application Software
 Utility Software
 Malware

 Viruses
and worms
 Trojan horses
 Spyware and adware
Practice
http://software.ucdavis.edu „
 Click on Antivirus software „
 Sophos
 Enable automatic update

 Windows
 Mac:
http://support.apple.com/kb/ht1338
The operating system
The operating system
Definition found on Wikipedia:
“An operating system (OS) is the software that manages the
sharing of the resources of a computer and provides
programmers with an interface used to access those resources”
Most common operating systems:
- Windows, DOS (Disk Operating System) (desktops, laptops)
- Unix and variants, including Linux (servers)
- MacOS
- Chrome OS
Operating system
Resource management and user interface
 What resources?

Operating system
Process management
 Memory management
 Disk and file system
 Event management and Device drivers
 Output device management
 Networking
 Graphical User Interface
 Security

Process management
Multitasking
 A process

 Running,

ready, blocked
Time slicing and task switching
File management
Logical and physical structure
 mapping

Memory management:
Current computers organize memory resources hierarchically,
from registers, CPU cache, RAM and disks.
The virtual memory manager coordinates the use of these resources by tracking
which one is available, which is to be allocated or deallocated and how to move
data between them.
Thrashing
Page Fault
 Thrashing: in the extreme case, there are „
so many active processes competing for
main memory that the computer spends
most of its time swapping pages.
 What can you do?

Event management

An event is a specific action that produces a reaction in
some program.




Device driver




Type a letter
Move the mouse
Time display
a computer program allowing higher-level programs to interact
with a hardware device
Hardware specific and operating-system dependent
Output device management
Press a key “S” in writing your term paper
The operating system
Most operating systems come with an application that provides a
user interface for managing the operating system, such as a
command line interpreter or graphical user interface (GUI).
Operating systems provide a software platform on top of which
other programs, called application programs, can run.
Your choice of operating system determines the applications you
can run.
Interaction between operating systems and microprocessors
Questions:

Is web browser a part of an operating
system?

Is multimedia play a part of an operating
system?
Popular Operating Systems








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Windows
Unix
Linux
MAC OS
Palm OS
Android
Windows Mobile
Symbian (obsolete)
Blackberry 6 OS
Suite and component

Suite
A
set of applications, e.g., Office 2007
 Interoperability
 Sharing code/functionality
 Similar feeling

Component
 With
standard interface for interoperability
 COM: common object model
 CORBA: common object request broker architecture
Web-based Applications






An application that is accessed via web browser over a network
A computer software application that is coded in a browsersupported language (such as HTML, JavaScript, Java, etc.) and
reliant on a common web browser to render the application
executable.
Advantages: Little disk space, automatic upgrade, integrate with
other web …
procedures, cross-platform compatibility, mobility friendly,
business reasons
Limits: Internet connectivity, inconsistency in browser
implementations, …
(currently) limited functionalities
Applications: webmail, online sale, wikis, etc.
Why did Google develop Chrome/Android?
An example

Google application suite
Progression
Hardware
 Software
 Service

 Computing
as a service …
 Software as a service …
 Storage as a service

Ex: http://aws.amazon.com/products/
Software

What is the difference between
Internet „Explorer and Chrome?
Software
Proprietary „
 Open-Source

A few practical tips
The computer fails the POST tests „
 Likely cause: One of the essential devices
is either failing or is missing
 Try: „

Check for any loose connections
(keyboard,
mouse,…}
 Check that the fans are working …
 Swap memory

The computer is thrashing „
 The computer all used all its RAM
resources „and starts using the hard drive
as alternative memory, slowing down
significantly.
 Try: „


Close all applications you are not using
anymore …
 Get more memory for the computer
The computer becomes very hot „
 Most probably one of the fans is
not „working anymore
 Detect fans that are not working
and „replace them



The computer “freezes” (i.e. becomes non „responsive)
There are many possible reasons: „




it looks as if it is frozen The computer may be thrashing …
one application has crashed …
the Window manager is down …
Unfortunately, often the only solution is to restart
the „computer (either by turning it off first or in the worst
case by unplugging it, or by pressing continuously on the
on/off button.