Computers

Software

Computer Layers

Hardware

BIOS

Operating System

Applications

Software Classifications

System Software (operating system) Application Software Utility Software Malware

Viruses and wormsTrojan horsesSpyware and adware

Practice

http://software.ucdavis.edu „ Click on Antivirus software „ Sophos Enable automatic update

WindowsMac: 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. Type a letter Move the mouse Time display

Device driver 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

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

The operating system

Questions:

Is web browser a part of an operating system?

Is multimedia play a part of an operating system?

Popular Operating Systems

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 browser-

supported 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.