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Operating Systems - Computer Studies Form 1


When acquiring computer hardware and software resources you need to make a number of considerations. In this lesson, we are going to discuss some of the factors to consider.

Lesson objectives

By the end of the lesson, you should be able to:

1. Identify hardware specifications when acquiring computer hardware.

2. Identify factors to consider when acquiring computer software.

Selecting a Computer System

In this lesson, we shall learn how to select a computer system by considering hardware and software


By the end of the lesson, you should be able to :

1. Identify hardware specifications when acquiring  computer hardware.

2. Identify factors to consider when acquiring computer software.

Background Information

The learner should have background knowledge of the following:

1. Computer hardware

2. Computer software

3. Setup and cabling


1. Read the advertisement of a computer sale below and drag the specifications into their corresponding hardware considerations

Hardware considerations

To buy hardware one needs to consider the following:

1. Processor

2. Memory capacity

3. Upgradeability

4. Compatibility

5. Cost

6. User needs

7. Warranty

8. Service support


The decision to select a particular processor depends on the number of available processors from different manufacturers including: Intel, AMD and Cyrix. Intel has two versions i.e. intel and intel celeron. Intel celeron are cheaper because they have less registers.

Processors are of different speeds e.g. an Intel Pentium IV has a speed of 3GHz. The speed of the processor gives it its power. The higher the speed, the more powerful the computer.

Therefore when selecting a computer/processor, you may consider the manufacturer, cost and the processor speed.


Memory capacity

Other than the processor speed, the processing power of the computer is also determined by memory capacity. the bigger the memory capacity, the faster the processing power.

It is advisable to acquire the right capacity of memory because there are certain software that require a certain minimum amount of memory to run comfortably. For example to run windows XP Microsoft recommends 128Mb of RAM.

128mb Memory Chip




This is the ability to attach specific parts and install more software in order to have more processing power.

Due to rapid change in technology, some computer devices may be rendered obsolete. Therefore there is need to acquire a computer that is easily upgradeable.


A computer is said to be compatible if it can interact with existing hardware devices. For example, one type of memory module may not be compatible with a particular type of computer.

However the current trend is for compatibility across platforms. For example manufacturers are producing devices which are compatible across the platform i.e. in both IBM and Apple computers.


The cost of an item is another key factor that dictates what you can afford.

The cost is determined by :

1. Processor make and speed

2. Memory size

3. Computer physical size

4. And the manufacturer

Therefore it is important to shop around for what your budget can accommodate.


If your work involves a lot of travel e.g. salesmanship then you need a computer that you can carry around with you.

Therefore the computer to choose is dictated upon by its portability. Laptops come in handy in such instances.

User needs

It is important to consider the users special needs when acquiring hardware because they may require special type of hardware. For example, the blind may need brail keyboard, speakers etc.

The user needs also determine the kind of software to be used which in turn determine the hardware to be used. For example design tasks require graphics software which in turn require high resolution display units, large hard disk etc .


A good computer offer should include a warranty. This means that should the computer malfunction, the vendor should be able to offer repair service free of charge. The warranty period in most cases range between six to twelve months.

It is therefore important to choose an offer with a warranty because it can save on repair costs.

Service support

These include follow up services such as initial installation and repair works. This is important because you are assured of expert service rather than use quarks.


Choose whether the following statements are True or False

The user needs, like the nature of work determines the kind of software to acquire

The portability of a software is not an important factor to consider when selecting a software.

Software considerations

Although you may have a powerful computer, you may not achieve your goals if you dont have the necessary software.

Some of the factors that you need to consider are:

1. Authenticity

2. Reliability

3. User needs

4. User friendliness

5. System requirements

6. Compatibility

7. Cost

8. Portability

9. Documentation


Authentic software is one that is protected by End User License Agreement (EULA). EULA spells out the condition that the user need to abide by before using the software.

Therefore it is illegal to acquire pirated software that is not accompanied by the EULA certificate of authenticity. The software must come with a warranty.


Software is said to be reliable if it is giving the expected output when given the neccessary input.

Select software that has been widely tested by several users and proved to be reliable.


Software that works without crashing and is considered to be error free.

User needs

The kind of tasks you intend to accomplish determines the software you acquire. For example document preparation tasks will need a word processor while drawing may require graphics software.

User friendliness

Human computer interface can either be graphical, menu driven or command line. Most users today go for graphical interface because it is more user friendly than the command line.

Special situations may also determine the kind of software you acquire. For example, the blind might need software that produce sound output in addition to text output.

System requirements

Read the documentation that comes with the software to see whether your system meets the minimum or recommended hardware requirements.

Every software requires some minimum system specifications for it to run on a computer.These are considered in terms of processor speed, memory capacity, hard disk size and display specifications. 


This is the ability to install and run software in more than one computer of different models. Such Software is referred to as portable.


Software compatibility refers its ability of a software to work smoothly in cross- platform. In the real world there are two platforms either IBM / PC compatible or Macintosh . In choosing an application software consider the possibility of running it on different machines with different operating systems. 

Therefore software developers are working towards software that are portable and compatible . A good example is Adobe PageMaker(R) that can work in commonly used versions of Windows, Linux and Macintosh operating.


As is the case of computer hardware, cost can also be a limiting factor in software acquisition. This makes the user sometimes look for cheaper alternatives such as freeware which may be unreliable.


Documentation refers to the user guides provided by the software manufacturer alongside the software. These guides may be in form of printed manuals, on-line help, Tutorials and any other form helpful to the user.

You need to select software that is accompanied by good documentations A good documentation has clear instructions on how to run the program.


Ability to add new features and functions to enhance existing software.

From time to time, most software developers strive to provide new versions or upgrades of their products. Some of the reasons for doing so is to:

1. Satisfy changing user needs

2. Enhance reliability and compatibility

3. Competition from other software houses

Prior Knowledge

In order to understand this lesson, you need the following skills:

1. Mouse Skills

2. Keyboard Skills

Let us review these skills using a practical activity:

Practical activity

Carry out the following mouse related activities

1.Point at My computer icon and click it. What do you observe?

The icon is highlighted

The icon disappears from the desktop

2.Point and double- click on My documents icon. What do you observe?

The icon opens

The icon moves to another location

3.Drag the My Network places icon to the top right corner of the desktop. What happens?

The icon disappears

Icon is moved to the top right corner

Carry out the following keyboard related activities:

Start WordPad from the Programs menus Accessories group,

Type the text below as it appears in :

1.Press Ctrl and S simultaneously to save the text Jaribio 

2.Press Alt and F4 simultaneously to exit WordPad.

Lesson objectives

By the end of the lesson you are expected to:

1.Define an operating system.

2.State the functions of an operating system

3. State types of operating systems

4. Describe how an operating system organizes information

5. Create files and folders/directories using an operating system

6. Work with files and folders/directories using an operating system

Operating system is a topic on its own. Under this topic the topic file management is covered.


Operating System

Organisation of information using an Operating System

In this lesson we are going to demonstrate the concept of information management using Microsoft Windows as an operating system.

Windows organizes information into drives, folders/directories and files.

A file is a collection of related data or information given a unique name for identification. For example Your class register if keyed into a computer it may be given a name like (Form1Register).

A folder is named storage location for storing related files for ease of access. Some operating system refers to it as a Directory . For example all the registers for all the classes can be stored in a folder called (StudentsRegisters). You can create more folders within a a folder, these are called subfolders. 

A drive refers to a physical or logical storage location on an auxiliary storage media. For example the default hard disk is identified as a drive C: The drive letters range from A-Z and denoted by a letter followed by a colon.

In summary, Windows organizes information into files, folders (or even subfolders) and drives. The chart below shows a tree structure of information storage in drive C:

Creating folders and subfolders

To create folders you need to identify the drive in which the folder will reside.

For example let us create a folder called Registers in the local drive C. To do this:

1.Right-click My computer icon.

2. In the shortcut menu click Open. What do you observe?

- My computer window is displayed

- Drive C: is opened

2. In My computer window, double click drive C: How many files and folders are displayed?

_________ files __________ folders

_________ files __________ folders

4.Click the file menu then point to New, then click folder. A folder with a name New folder is created. Note that the folder name is highlighted

5.Type the word Registers to replace the temporary folder name.

6. Press the enter key.

The folder Registers is created.

Creating files

To create a file you need to identify the drive and the folder in which the file will reside in.

For example let us create a text file called Fees in the local drive C: in the folder you have created i.e. MySchool. To do this follow the following steps:

Open the application e.g Wordpad or Wordprocessing.

Click on filemenu

Under save in option, select the folder ie MySchool

Under save as option, type the name of the file

Click on Save.

Creating folders and subfolders

To create folders you need to identify the drive in which the folder will reside.

For example let us create a folder called Registers in the local drive C. To do this:

1.Right-click My computer icon.

2. In the shortcut menu click Open. What do you observe?

- My computer window is displayed

- Drive C: is opened

2. In My computer window, double click drive C: How many files and folders are displayed?

_________ files __________ folders

_________ files __________ folders

4.Click the file menu then point to New, then click folder. A folder with a name New folder is created. Note that the folder name is highlighted

5.Type the word Registers to replace the temporary folder name.

6. Press the enter key.

The folder Registers is created.

Working with files and folders

Now that you have learnt how to create files and folders, let us see how you can manage them using windows explorer. In this lesson we shall look at how you can:

1. View contents of a folder or drive

2. Expand and collapse the folder tree 

3. Copy and move a file or folder

4. Rename a file or folder

5. Sorting files in a folder

6. Search for a file or folder

7. Delete a file or folder

Viewing files and folders

Files and folders can be viewed using the Windows Explorer. The explorer lists folders and their contents in two window panes.

To view windows explorer, proceed as follows:

1. Click on the start button

2. Select programs, accessories then windows explorer.

Note: You can also start windows explorer from the Start menu or by pressing the Windows logo key together with the letter E.

Look at the folder listing in the left pane. Some folders are preceded by a positive sign.

Click the positive sign. What do you observe?

1. Subfolders within the selected folder are displayed

2. The selected folder is moved one place down

On clicking the plus sign in front of a folder expands the tree and the sign is replaced by a - (minus) sign. This is referred to as Expanding the tree.

Click the - (minus) sign of the expanded list. What do you observe?

1. Subfolders within are hidden

2. The selected folder are deleted

On clicking the - (minus) sign in front of a folder collapses the tree and the sign is replaced by a + (plus) sign. This is referred to as Collapsing the tree.

To view the content of a folder, click a folder on the left pane of the explorer window.

Note: If a subfolder contains subfolder (s) in it, it will be preceded by a + (plus) sign.

Copying files or folders to a different location

1.To copy a file or folder to e.g. secondary storage proceed as follows

2.Insert the secondary storage medium into the  drive.

3.Open the windows explorer.

4.From the left window pane, click the folder or file you want to copy.

5.From the Edit menu, click the Copy command.

6.Select the location; a folder on the secondary storge medium where you want to place the copy.

7.Click Edit menu once again then click Paste. A duplicate copy is placed in the new location

Moving files or folders to a different location

To move a file or folder to e.g. to a different location, proceed as follows:

1. Select the destination e.g. the floppy drive.

2. Select the file or folder you want to move.

3. From the Edit menu, click the Cut option.

4. Select the destination the file or folder is to be moved to.

5. Click Edit menu once more then click Paste. The target file or folder is moved to the new location

Renaming a file or folder

Renaming is the process of changing the name given to a particular file .

To rename a file:

1. Open the windows explorer
2. Select the file or folder you want to rename
3. From the file menu, select the command rename. The old name is highlighted
4. Type in the new name then press the enter key.

Look at the illustration that shows this procedure next.

Sorting files

Windows automatically sorts items alphabetically in ascending order or descending order. However you can sort the items manually by categories such as by name, date size, type and date modified. To do this;

1. Open the drive or folder that contains the items you want to sort

2. Click the view menu, point to Arrange Icons by, and then click the appropriate sort command.

Deleting files and folders

Delete refers to erasing or doing away with an item. This is a sensitive command that needs to be exercised with extra caution otherwise you may loose important data.

Before we carry out this task, let us first explain what happens when you delete an item from removable device such as the floppy or from the hard disk.

Deleting items from the hard disk

When you delete any of these items from your hard disk, Windows places it in the Recycle Bin.

Items remain in the Recycle Bin until you decide to empty the recyle bin or restore back to their original location . Therefore the Recycle Bin is a safety measure in windows that helps in holding files that may have been deleted from a hard drive by mistake. 

Deleting items from a removable drive

Items deleted from a removable drive such as a floppy disk are not sent to the Recycle Bin.

To delete a file or folder;

1.Open Windows explorer and select the drive that contains the item to be deleted

2.Click the file or folder you wish to delete

3.From the explorer menu, click the File menu and then Delete. The File is deleted.

Note: You can also delete an item by right-clicking it and then clicking Delete.

Click Next to try and Delete using the shortcut menu.

Existing files can be deleted from their storage location and media.

To delete a file or folder from a computer;

1. Open the location where the file /folder is save

2. Click on the file to select

3. Go to file menu and select delete

4. The following dialogue box opens and prompting you to confirm delete.

5. Point and select yes to delete and NO to retain the file

When a file or folder is deleted it is temporarily stored in the recycle bin. A recycle bin is a system folder that acts as a buffer location for deleted files and folders.

Note1. there are shortcuts for carrying out these activities.

To delete a a file or folder tap the delete key from the keyboard and confirm delete dialog box opens.

You could also delete by pointing at the file/folder to select, right clicking and from the shortcut menu, clicking on delete

Note 2. Deleted files can be restored from the recycle bin.

To view deleted files in the recycle bin:

1. From the desktop, point and double-click on the recycle bin icon on the desktop to open it.

2. Select a file/folder you want to restore.

3. From the file menu, select restore.

You could also restore a file using shortcut menu. To do this:

Open the recycle bin, point to a file or folder you want to restore, right click and from the shortcut menu select restore.

Note 3. Files can be permanently deleted from the recycle bin. Once this is done these files and folder cannot be restored.

To empty the recycle bin, open the recycle bin by double clicking.

From the edit menu click on select all to select all the files and folders in the recycle bib

From the file menu, select delete.

A dialogue box opens and prompts you to confirm delete.

By clicking yes the content of the recycle bin are permanently deleted.

Searching for files or folders

Often users forget where they might have saved their files and folders . An operating system provides a way for searching files and folders under its control.some of the criteria used to search include:

1. name

2. date and time of modification

3. file type

4. size of the file

To search for a missing file or folder using a Windows operating system, the following procedure should be followed:

1. Click on the start button.

2. Select search

3.Click on files or folders.

The following are the search options for windows XP operating system:

The search options enables you to search for:

1. picture, music or video files

2. Specific application files such as word, excel, Access etc.

3. All files and folders in the computer.

Under each of these options, more distinctive options are provided such as keywords and search location.


Definition: It is a software that controls the hardware and the software resources and the actvities that take place in a computer.

It also creates a link between the liveware, the hardware and the software.

Some of the resources are:

- Input/output devices eg Keyboard, mouse,printers

- communication devices eg. modems, network cards


Operating systems are classified according to three criteria:

1. Number of Users i.e. Single user and Multi-user

2.Number of programs/Tasks


A single user operating system allows only one program to run at a time. This means that if you are working in a spreadsheet and want to write a memo, you must shut down the spreadsheet application and open up a word processor. This is annoying, especially if you need to quote some data from the spreadsheet in your memo! So new operating systems were designed that allowed multiple programs to run at the same time.

The simplest form is multi-tasking. What this really means is that the programs are taking turns with the processor. It allows a single user to have the spreadsheet and the word processor open at the same time, and even more. Now the user can see to copy data from one to the other. Much better!!

The computer must decide on how many time slices each program gets. The active program gets the most. Next is programs that are doing things but which aren't the foreground program. Last is programs that are open but aren't doing anything. They need a little bit of time every now and then to see if they are supposed to do something yet.

The next step up in complexity is multiple users. On a network several users can be using the same computer or even the same program on that computer. This is called time-sharing.

If a computer has multiple CPUs, it can do multiprocessing. Rather than a single CPU giving out turns to various programs, the different CPUs can work simultaneously. Speed increases immensely. Of course cost does, too!

It is possible for a computer to use more than one operating system through the use of virtual machines."Virtual" means it's not really there. But programs written for different operating systems are fooled into thinking their required operating system is present.


The functions of an operating system are:

Operating system: computer pointing to functions

1. Input/Output handling

Flow control is also part of the operating system's responsibilities. The operating system must manage all requests to read data from disks or tape and all writes to these and to printers. 

To speed up the output to printers, most operating systems now allow for print spooling, where the data to be printed is first put in a file. This frees up the processor for other work in between the times data is going to the printer. A printer can only handle so much data at a time. Without print spooling you'd have to wait for a print job to finish before you can do anything else. With it you can request several print jobs and go on working. The print spool will hold all the orders and process them in turn.

2. Memory management

Memory must be managed also by the operating system. All those rotating turns of CPU use leave data waiting around in buffers. Care must be taken not to lose data!! One way to help out the traffic jam is to use virtual memory. This includes disk space as part of main memory. While it is slower to put data on a

Swapfilehard disk, it increases the amount of data that can be held in memory at one time. When the memory chips get full, some of the data is paged out to the hard disk. This is called swapping. Windows uses a swap file for this purpose.

3. Job Scheduling

Time in the CPU is divided into time slices which are measured in milliseconds. Each task the CPU does is assigned a certain number of time slices. When time expires, another task gets a turn. The first task must wait until it has another turn. Since time slices are so small, you usually can't tell that any Time slices

sharing is going on. Tasks can be assigned priorities so that high priority (foreground) tasks get more time slices than low priority (background) tasks.

4. Error handling

5. Interrupt handling

6. System Security

Some system security is part of the operating system, though additional software can add more security functions. For multiple users who are not all

System security - computer with lockallowed access to everything, there must be a logon or login procedure wherethe user supplies a user name or ID and a secret password. An administrator must set up the permissions list of who can have access to what programs andwhat data.

Originally the operating system was created by each company that manufactured a processor and motherboard. So each operating system was proprietary, that is, unique to each manufacturer. Problem: changing to a new computer meant your software had to be replaced! Not good marketing. So there was pressure early on to standardize things so that software could be transferred to the new (and of course better!) computer. This required more standardization in operating systems.

The winner in the PC market was MS-DOS, Microsoft's Disk Operating System, and its twin at IBM, PC-DOS, also written by Microsoft. Now it's hard to recall those days when each computer had its own unique operating system.

Windows 95 and Windows 98 are actual operating systems on their own. The previous versions of Windows use DOS as the operating system and adding a graphical user interface which will do multitasking. But with Windows 95 Microsoft released an operating system that can take advantage of the 32-bit processors.

Windows Me (Windows Millennium Edition) is an upgrade of Windows 98, release date Sept. 14, 2000. The system resources required for this operating system are significantly higher than previous versions of Windows.

Windows NT (the NT apparently came from New Technology) is an operating system for client-server type networks. The last version of NT has a user interface that is practically identical to Windows 95. Since Windows NT was designed for the higher demands of networks, it had higher demands itself for disk space and memory.

Windows 2000 is an upgrade of Windows NT rather than of Windows 98.

Windows XP is an upgrade to Windows 2000. It comes in two versions - Home and Professional. The Professional version contains all the features of the Home version plus more business features, like networking and security features.

Windows Vista was released in early 2007. It has higher requirements for memory and processor speed than previous versions of Windows. Vista comes in several different flavors for home and business purposes.

Windows CE is for small devices like palmtop and handheld computers. Lite versions of a number of major applications are available to run on these devices. You can link your small computer to a regular one to synchronize documents and data.

The Apple Macintosh is a multitasking operating system that was the first graphical interface to achieve commercial success. The Mac was an immediate success in the areas of graphics production, and still commands the lion's share of that market. Apple made a major marketing error when they decided to keep their hardware and software under tight control rather than licensing others to produce compatible devices and programs. While the Apple products were of high quality, they were always more expensive than comparable products that were compatible with Microsoft's DOS operating system. This is an example of how a near lock on a market can be lost in a twinkling.

The current version is Mac OS X, which is version 10. Since January 2002, all new Mac computers use Mac OS X. Subversions are named Jaguar, Panther, Tiger, Leopard....

IBM's 32-bit operating system, OS/2, was a popular system for businesses with complex computer systems from IBM. It was powerful and had a nice graphical interface. Programs written for DOS and Windows could also run on this system. This system has never really caught on for PCs and is no longer marketed.

UNIX is an operating system developed by Bell Labs to handle complex scientific applications. University networks are likely to use UNIX, as are Internet Service Providers. A lot of people have experience with UNIX from their college work. Many computer old-timers love UNIX and its command line interface. But all those commands are not easy to remember for newcomers. X-Windows is a graphical interface for UNIX that some think is even easier to work with than Windows 98.

Linux is an operating system similar to UNIX that is becoming more and more popular. It is a open-source program created by Linus Torvalds at the University of Finland, starting in 1991. Open source means that the underlying computer code is freely available to everyone. 

Programmers can work directly with the code and add features. They can sell their customized version of Linux, as long as the source code is still open to others.

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