Operating Systems

Foundation Computing

Half the people you know are below average.

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OverviewOperating systemsApplication SoftwareSecurityFilesA mystery

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Operating systemSits between the user (you) and the

physical hardwareMakes tasks simple - you don’t need to be

a programmer to use a computerCommand line environment vs graphical

user interface (GUI)Customization

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Operating systemSits between the user (you) and the

physical hardwareMakes tasks simple - you don’t need to be

a programmer to use a computerCommand line environment vs graphical

user interface (GUI)Customization

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Operating system (2) Is responsible for

Running and scheduling of programs (processes) Hardware management Memory allocation Networking (communication with other computers) Security (administrator, restricted permissions for users) File management And more!

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Examples of popular OS's

UnixMac OSWindowsLinux (free, open source)

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Application softwareIs not part of the OS, although it may be

sold in the same packageAllows the user to perform a certain taskExamples:

Word processing software Games Web clients (browser, email) Database software

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Security

Security flaws (install updates)Firewall (make sure it is turned on)Virus Protection (scan regularly!)SPAM FiltersNever open an email attachment from

a stranger! Archiving/backup

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Virus SoftwarePopular Brands of Virus Software:

Symantec (USQ staff use this) Norton's PC-Cillin AVG (free version:

http://www.grisoft.com/)

Update the virus database regularlyScan your system regularly

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A house or business

Firewall

You will sometimes need to turn it off Firewalls prevent communication.

Don't forget to turn it on again later!Firewall is often contained in ADSL modem

GW

PC PC

PC

Firewallneeded here.

Internetnot needed here.

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Files – get organised Files are used for

Documents Graphics Music Data

Files are organised in: Directories (folders) CD's Archives

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File Systems

Files are stored in file systems.Your computer may need to check or repair

your file system from time to time.Turning off without shutting down may

damage the file system.

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Files (2)Hierarchical structureFiles have a name and a suffix

Windows does not necessarily display the suffix

In Windows the suffix is used to identify the file type, eg letter.txt

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Files (2)

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Files (3)Text files:

Contain only text (ASCII)No fancy fonts, symbols, images etcJust characters you can type from the keyboard

Can be viewed in simple text editor like notepad

Examples: Files with .txt extensionHtml filesSource code from most programming languages

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Files (4)Binary files

Executable programs (eg .exe) Application specific formats (.doc, .xls, .ppt) Graphics, multimedia (.jpg, .gif, .mp3) Usually not easily readable if opened in

Notepad

Open with Word Open with Notepad

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Files (5)Windows associates file extensions with

an application, eg: .txt -> opened in Notepad .doc -> opened in Word .html -> opened in Internet Explorer

The icon indicates which application is associated with a file

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Binary numbersAll computer data is stored in the binary

number systemOnly uses 0 and 1

(binary=2 digits, decimal=10 digits)

One bit is either 0 or 1One byte is 8 bits

(28=2x2x2x2x2x2x2x2=256 possible values)

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File Size Units1024 (=210) major scaling factor 1 KB (kilobyte) =1024 bytes (B)1 MB (megabyte) = 1024 KB1 GB (gigabyte) = 1024 MB1 TB (terabyte) = 1024 GB

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A mystery I bought a hard disk with a size of 40 GB Why does my computer tell me it can only store

37.3 GB?

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A mystery (solved) I bought a hard disk with a size of 40 GB Why does my computer tell me it can only store

37.3 GB? Answer: Hard disk manufacturers use file size

units in a different way: They gave me 40,000,000,000 B and divided by 1000

each step, not by 1024, to reach GB But we know 40,000,000,000 B = 39,062,500 KB =

38,147 MB = 37.3 GB !!!