Operating SystemsMr Conti4th April 2014

Operating Systems

An operating system (or OS) is a computer program which controls everything the computer does.

What is an operating system?

New computers usually come with one installed.

You cannot use any other program (software) without an operating system.

You can’t do anything without me!

Yes, but what does it do?You probably don’t think about it, but while you’re doing the interesting stuff, your operating system is:

handling communications between software and hardware

allocating computer memory and CPU time organizing how data is stored on backing storage.

OK printer, word processor says print it

now, spreadsheet you’ll have to wait!

No, no, CPU, I said save first then check for e-

mail!Now, if I put that there because that file was deleted, then this will fit there. Now where did I put that other

one?

CommunicatingAt any one time, your computer might be:

loading and saving data and programs

The operating system has to communicate with the hardware and software and manage the tasks, so that the system cannot, for example, try to read from and write to a floppy disk at the same time.

Because the operating system manages what the software does, most pieces of software need a particular operating system to run on.

displaying information on the monitor.

communicating with peripherals such as a mouse or a printer

Managing Computer MemoryEven though you think you are only doing one thing on your computer, like working with a spreadsheet, computer memory must be allocated to each task the computer is doing.

Memory would be used to:

store the spreadsheet program

store your spreadsheet file store a copy of the image

that is being displayed on the monitor

run the operating system.

Managing Computer MemoryMost computers only have one microprocessor in their CPU, so can only do one thing at a time.

The operating system splits CPU time into tiny slices, and allocates each task some time, so it appears as if the computer is doing many things at once – multitasking.

If you were printing the first page of your spreadsheet while working on the second one, the CPU’s time would need to be divided up between:

letting you enter more data on the keyboard

The operating system helps to manage which tasks take priority.

printing sheet 1 displaying what is going on via

your monitor.

Types of Operating System

MS-DOS A simple, command-driven operating system used on personal computers (PCs).

Windows An operating system used on most PC computers.

UNIX A multi-user, multi-computer operating system which is used on large mainframe computers and networks.

OS X An operating system for Apple Mac computers.

Command Line InterfaceOlder operating systems such as MS-DOS are often called Command Line Interfaces or CLIs.

They are text based, and the user has to type in what they want to do using commands the computer will understand.

They work very quickly, and don’t use up many system resources such as memory or hard disk space, but they are difficult to use unless you know the commands really well.

Menu Based InterfaceMenu-based interfaces were developed to make things easier. Instead of typing in a command, you could choose one from a list on the screen. They are still text-based, and can be slow because you have to follow a set route to do anything. Like CLIs, they don’t use up lots of resources.

Mobile phones are a good example of a menu-driven interface.

Welcome to the KS4 SystemPress:1 for Hardware2 for Software3 for Networks

Graphical User InterfaceGUIs or Graphical User Interfaces are much easier to use.

They use pictures called icons to represent files or buttons, and the user clicks on the button with a pointer moved by a mouse.

This isn’t a real calculator, it’s a GUI that represents one.Clicking on icons with a mouse or pointer is easier than having to type in the numbers for the calculation in a format the computer will understand, as would happen in a CLI. The interface converts the mouse clicks into code for us.

WIMPMany people these days like WIMP.

WIMP stands for Windows Icons, Menus, Pointer, and many of the interfaces we are used to are WIMP environments.

Finding Things

Memo

To: J. Vincent

From: S. Sanghera

Re: Meeting

Please bring your notes with you,

When we have papers to file, we put a:

Safety Meetings

Meetings

We label folders and

drawers

Folder

Filing cabinet

into a

into a

File

Tree Diagram

Root c:main directory

A file is one document.

A directory (folder) is a storage area for files that have something in common.

Directories can be split into sub-directories.

Directories(folders)

Sub-directories(folders)

The operating system helps us to organize computer files.

File Names

A file name is split up into two parts: the file name and the extension. For example:

This part is the filename, and is usually chosen by the user.

This part is the extension, and is usually added by the software.

safetymemo.doc

 The two parts of the filename are separated by a dot.

Sorting Files

You could keep all the files from the same program together in a folder.

Or all the files for the same topic.

The operating system associates a program with each file type.

When you double click a document ending in .doc, for example, it will usually open it in the word processor.

There are lots of ways you can organize your files, and it doesn’t matter too much as long as you can remember how you did it.

It will depend on what you actually have to store.

Emma’s directory on the school network is in a mess. All her files are in one folder and she has to search through them all to find anything.

In music, she has been working on a project about composers. She has lots of files about ICT topics. She has also been using a spreadsheet for her maths coursework

and a desktop publishing program for the other projects. She has decided to put all the files for the same kind of program

together in a folder.

Reorganise Emma’s directory and put the correct files in the corresponding folders.

Word Processing – Desk Top Publishing DTP – Spreadsheets - Graphics

Task

Emma now thinks it might have been better to group her files by subject, rather than file type.

Reorganise Emma’s directory and put the correct files in the corresponding folders.

Music– Maths– ICT

Extension Task

An operating system (or OS) is a computer program which controls everything the computer does.

The operating system: handles communication between software and hardware; allocates computer memory and CPU time; and organizes how data is stored on backing storage.

The operating system helps to manage what gets priority when multitasking.

There are four types of interfaces: Command Line Interfaces (CLI), menu-based interfaces, Graphical User Interfaces (GUI) and Windows Icons, Menus, Pointer (WIMP).

The operating system helps us to organize files in folders.

Summary