OPERATING SYSTEM

[the_ad id=”1178″]

OPERATING SYSTEM

Introduction

Definition of Operating System

OPERATING SYSTEM-A set of complex programs that work together to control execution of user programs called applications.

Examples:

MS Windows, UNIX, LINUX, Macintosh (Mac OS) and OS/2.

Functions of an operating system software 

(i)         Memory allocation & loading of programs

–           Loads application programs from an external storage into the available locations in the Main memory (RAM)

–           It keeps track (monitors) of the parts of the memory that are in use, and those which are free

(ii)        Processor management:

[the_ad id=”1178″]

The processor can only execute one program at any one time. Therefore, in a multi- tasking system access to the CPU must be carefully control & monitored. The OS must decide, which program will be allowed into the system, and for how long

(iii)       Job scheduling

It schedules & loads programs in order to provide a continuous sequence of processing. This is necessary when more than one application program is occupying the main storage

(iv)       Error reporting and interrupt handling

The OS reports any errors that occur during program execution.

(v)        Management of CPU time

In a multi- taking  system where several user programs share the computer  resources, the processing is done according to the  job  priorities allocated and in a continuous process until all the jobs in the queue within the  memory are executed. This ensures that the CPU does not remain idle at any given time.

[the_ad id=”1178″]

• Manages the input and output devices

The OS controls the allocation of I/O devices and tries to resolve any conflicts that arise. It also monitors the state of each I/O device and signals any faults detected

• File management

OS is concerned with the logical organization of the files in the computer & provides ways for sorting, retrieving & sharing of the files

It also provides a means of protecting the data files & programs against unauthorized access and corruption.

It controls the selection & operation of the hardware devices used for input, output & storage

It interfaces the user to the system’s hardware, i.e. it provides a quick means of communication between the computer user and his programs

• Logging & accounting

The OS keeps records (internal logs) on how the computer resources (e.g. CPU time, memory, peripherals) are being used

It also keeps a complete record of all what happens during processing (usually in the form of a printed log)

[the_ad id=”1178″]

Operating System

Resources under the Operating System

•    Processor: The operating system arranges all tasks accordingly to prioritize and decides which task to continue and which task to stop.
•    Main memory: The operating system determines which task to remain in memory for execution and what to send back to backing storage to wait.
•    Input Output devices and ports: It controls the input of the data and output of information.
•    Secondary storage device: The operating system manages the storage (saving) and the retrieval of data and information in storage devices. It utilizes hard disk space by holding take not need currently by the RAM.
•    Communication devices and ports: Operating system controls the exchange of data and information.

Types of Operating System

Classification according to task handled currently

1. Single program operating system: It allows processing of only one program at a time like the Microsoft Disk Operating System (MS DOS)
2. Multitasking operating system: It allows a single CPU to execute more than one program at a time

Classification according to number of user

1. Single user operating system: Can only be used by one application at a time e.g. Windos95/98, MS DOS.
2. Multi-user/ multi-access operating system: can be used by more than one use at a time e.g. UNIX, LINUX, Windows NT/2000/XP/VISTA, and Novell.

Human Computer Interface (HCI)

This is a method of interaction between the user and the computer.

1. Command line interface: The user interacts with the computer by typing the command in the command prompt then pressing the enter key for execution.
2. Menu driven interface: They give the use a list of options to select from
3. Graphical user interface: It represents commands in form of graphics or icons.

[the_ad id=”1178″]

Operating System Consideration

1. Hardware configuration: memory size, hard disk capacity and the processor type.
2. Basic design of the computer
3. User friendliness and the human computer interface (HCI)
4. Availability in the market
5. Cost
6. Reliability: can it run without crashing/ hanging i.e. stop responding to commands

Common features in Windows Operating System

•    Similar interface/ interaction
•    Long file name
•    Plug n play (PnP) windows automatically accept a new hardware once installed
•    Support multi-tasking and multi-user

Factors that dictate how an operating system organizes information

• Rapid access: organization method should allow quick access to stored data.
• Ease of update: by keeping a record of the date modified.
• Economy of storage: should use the least storage possible because memory is a scarce resource.
• Simplicity of maintenance: organization method should enable quick navigation through the file system and make it easy for it to be maintained.
• Reliability: organization method must be reliable.

Properties operating system display about a file

•    Capacity
•     Location
•     Extension
•     Date

[the_ad id=”1178″]

Two types of Windows

1. Application Window:  Screen that appears when an application program is opened.
2. Document window: this represents the work area

File

Common storage unit in a computer where

Types of files

•    System files: files that contain information required for the operation of the computer
•    Application files: Files that hold programs or start an application. 

File Extensions

Importance

Examples DAT- data TXT- text

• DOC- document
• XLS- excel
• SYS- system files COM- command file BAK- back up
• PPT- PowerPoint
• BAT- batch file

Operating System

Folder/ directory: A named storage area created for storing files for easy access.

Subfolder: divided folder

Windows desktop: This is the first screen after successful booting.

Desktop Elements

Icons: This is the graphical/ pictorial representation of items.

Taskbar: It allows the user to switch between different files and programs. Start button: It displays the start menu.

Task manager: Display buttons of the current running tasks.

System tray: Has icons of tasks running in the background but not displayed on the screen.

[the_ad id=”1178″]

Parts of an application window

• Title bar: Display name of current application program or task. Minimize button: Reduces a window to a button on the taskbar.
• Restore/ maximize: It stretches a window to cover the entire screen or return to the original screen. Close button: Exits the document but not the application.
• Menu bar: provides a list of commands inform of buttons. Toolbar: represents shortcuts to menu commands.
• Work area/ document window: Where data is being entered.

Disk management

• Formatting: Preparing a disk for use by imprinting tracks and sectors.
• Scanning:  -scanning for virus
• -scanning for errors: SCANDISK: Check up for minor storage problems e.g. lost storage location or damaged surface
• Defragmenting: Re-arranging scattered folders to speed up access and retrieval.
• Compressing: Squeezing disk contents to free space on the media.
• Backing up data: Creating duplicate copies of data on separate storage device for security purposes.
• Boot up (start-up)/ system disk: System disk created to start the system in case the components of starting up fail or when the hard disk is seriously damaged. The booting instructions are copied on the disk.

Partitioning: Subdividing a large physical disk into two or more portions called logical drives. Reasons for disk partitioning:

•    When user intends to install more than one operating system on the same disk.
•    For back up purposes

[the_ad id=”1178″]

Troubleshooting Windows Related Problems

•     This is a process of diagnosis and trying to fix hardware or software related problems.
•     Some problems Windows experience
•     Failure to boot
•     Computer hanging now and then
•     Abnormal restart 

These problems may result from

1. Problem in installing process missing files
2. Insufficient system memory
3. Problems with hard disk boot sector may be due to virus infection
4. Corrupted window registry system
5. Due to interrupt request conflicts

Operating System

[the_ad id=”1178″]

Solved KCSE Questions on the topic

1. The central processor and peripheral devices of a computer system are coordinated by the operating system

(a) Define the term ‘operating system’

• A set of computer programs that normally reside in the main memory and used to control the basic computer hardware resources & the operation of the entire system
• The main program that controls the execution of user applications, and enables the user to access the hardware & software resources of the computer

(b) List two resources/ components that an operating system manages

• –           Processor
• –           Memory (RAM)
• –           Secondary storage devices
• –           Input/ output devices
• –           Communication devices
• –           I/O & communication ports
• –           Files

(c) There are several types of operating systems in use today. State two examples of

Operating systems which you are familiar                                                      (2 mks)

• –           Disk Operating System (DOS)
• –           Windows
• –           MacOS
• –           Unix
• –           Linux

2. Name the two latest operating systems from Microsoft corporation(2 mks)

• –           Windows XP
• –           Windows Vista

3. Explain any four functions of an operating system software ( 8 mks)

[the_ad id=”1178″]

(i)         Memory allocation & loading of programs

• –           Loads application programs from an external storage into the available locations in the Main memory (RAM)
• –           It keeps track (monitors) of the parts of the memory that are in use, and those which are free

(ii)        Processor management:

The processor can only execute one program at any one time. Therefore, in a multi- tasking system access to the CPU must be carefully control & monitored. The OS must decide, which program will be allowed into the system, and for how long

(iii)       Job scheduling- it schedules & loads programs in order to provide a continuous sequence of processing. This is necessary when more than one application program is occupying the main storage

(iv)       Error reporting and interrupt handling- The OS  reports any errors that occur during program execution.

(v)        Management of CPU time:

In a multi- taking  system where several user programs share the computer  resources, the processing is done according to the  job  priorities allocated and in a continuous process until all the jobs in the queue within the  memory are executed. This ensures that the CPU does not remain idle at any given time.

• Manages the input and output devices

The OS controls the allocation of I/O devices and tries to resolve any conflicts that arise. It also monitors the state of each I/O device and signals any faults detected

• File management

OS is concerned with the logical organization of the files in the computer & provides ways for sorting, retrieving & sharing of the files

It also provides a means of protecting the data files & programs against unauthorized access and corruption.

• It controls the selection & operation of the hardware devices used for input, output & storage
• It interfaces the user to the system’s hardware, i.e. it provides a quick means of communication between the computer user and his programs
• Logging & accounting

The OS keeps records (internal logs) on how the computer resources (e.g. CPU time, memory, peripherals) are being used

It also keeps a complete record of all what happens during processing (usually in the form of a printed log)

[the_ad id=”1178″]

4. What is an interrupt?

An interrupt is break from the normal sequential flow of instructions processing in a program

5. Give three ways in which operating system are classified (3 mks)

• The number of users they handle
• The number of tasks they execute concurrently
• Human computer interface

6. Giving an example in each case, explain the following types of operating systems

(a)        Single – user / single tasking

A system that allows only one user to run one user program at a time in an interactive, conversational mode. E.g. Ms- DOS, PC- DOS.

          (b)        Multi- User/ Multi- tasking

A multi- user computer system can allow interactive facilities to several at a time. A Multi- tasking Computer system can allow more than one program which are in the memory to be processed at the same time. E.g. Microsoft Windows, Linux.

7. A computer user may interact with a computer either through Graphical  User Interface (GUI) or though typed commands

(a)        Give one advantage of using GUI based operating system over a command line interface  ( 1 mk

• User friendliness
• Easy to learn & use even by those  who do  not have much knowledge about them
• One does not need to master any commands
• It is faster to work with than a command line interface as it only relies on clicking the icons by use of a pointing device

(b) Some computer systems still use command line interfaces. State two advantages of command line interface

• –           They are more flexible than menu- driven interfaces
• –           There is security of data as only those who know how to use the commands will access it.
• –           They use cheap hardware & software facilities
• –           One has a better control over the system resources

8. What is a deadlock in reference to operating systems?

• –           It is a situation in an OS when a particular task holds a needed resource and refuses to release it for use by other tasks

[the_ad id=”1178″]

9. Explain briefly the following concepts as used in the windows environment:

(a)        Desktop

Desktop is mostly an empty screen that appears when windows starts and has some standard icons that show that the computer is ready for use.

(b)        Window

A rectangular area on a computer screen in which text, graphical images or the contents of a folder or disk may be displaced

            (c)        Icon

A little picture on the computer screen representing a program, disk file folder or any other item

            (d)        Sidekick menu

A submenu that appears either on the right or left of a main menu

            (e)        Taskbar

A long bar/ strip that runs across the desktop and displays the start button and any other active tasks.

            (f)        Task

Any activity taking place in windows and is displayed on the taskbar, e.g. running program                                                                                                          (3 mks)

10. Identify three functions of taskbar
    • Indicates what programs are running
    • Holds minimized programs
    • Provides a shortcut menu  for arranging  programs

11. State two differences between Disk Operating System (DOS)  and Windows operating system                                                                                             ( 2 mks)

[the_ad id=”1178″]

12. Identify three factors you would consider when choosing an operating system for use in a computer ( 3 mks)

(i)         Hardware configuration of the computer, e.g. RAM memory size, Hard disk capacity, type of processor, etc

(ii)        Basic design of the computer – It is an IBM compatible, or apple computer?

(iii)       Hardware compatibility

(iv)       User (type of work to be done), i.e. the applications intended for the computer

(v)        User friendliness or human computer interface, i.e. it is command line based, Menu driven or graphical user interface?

(vi)       Availability in the Markey, e.g. Microsoft Windows based operating systems are very common

(vii)      Portability

(viii)     Cost- how expensive the OS is

(ix)       Reliability, i.e. can it run without crashing (stop responding to commands)?

(x)        The method of communicating with the computer, e.g. the number of peripherals

(xi)       The method of operating the computer

13. Explain how windows organizes information in reference to files and folders

It stores related data & information records into files, and related files into folders & subfolders

14. (a) Distinguish between systems files and application files       ( 2 mks)

System files hold critical system information while application files hold programs data

(b) State the extensions used signifying the following file types                       (2 mks)

(i) Driver or system file – DLL, SYS, INI

(ii) Batch file – BAT

15. (a) List and explain down the three parts of the windows Taskbar ( 3 mks)
    • Start button – Provides access to the start menu
    • Task Manager – Displays buttons of currently running tasks
    • System tray – displays icons of applications that automatically start and run in the background

[the_ad id=”1178″]

(b) Outline the procedure of renaming a file or folder using windows operating system                                                                                                                                  (3 maks)

Method 1:

• In an explorer window, click the file/ folder you want to rename
• Click on file, choose rename
• Type the new name, then press enter

Method 2:

• In an explorer window, right- click the file/ folder you want to rename
• Choose Rename from the shortcut menu that appears
• Type the new name, then press Enter

16. (a) What is a dialog box?

Window that appears temporarily to request or supply information. It contains options (settings) one must select to complete a task

(b) List five settings that may be found in a dialog box

• Textbox- a box you can type data in
• List box – a box that contains a list of options, one of which is selected
• Checkbox- a small, square box that can be selected or cleared. It appears with an option that you can turn on or off. When the checkbox is selected, a selected, a checkbox (þ or x)appears in the box
• Radio button – a round button that can either be blank or can contain a dot. If the button contains a dot¤, it is selected.
• Pull down menu – A box with a downward – pointing triangular button at its right end (6). When the triangular button is clicked, it displays a menu.
• Command button- A button that can click to carry out or cancel the selected action. E.g. the OK or cancel button.

17. (a) Define ‘ folder/ directive tree’

Directory tree is the hierarchical arrangement of folders and storage locations from the root downwards.

[the_ad id=”1178″]

(b) Give two examples of root directories you know                                        (1 mk)

• –           A:\
• –           C:\
• –           D:\
• –           E:\

(c) Give three uses of sub- directories or subfolders                                        (3 mks)

• –           Used to store files that are not required currently until they are needed again
• –           Used to store the files of one program separately from the files of another program
• –           It allows each user to keep his/ her files separately, even if all the users are using the same systems.

18. The Hierarchical system represented below shows how a school organizes its files. Study it and answer the questions below.

The F2 directory has the files: classlist.doc, Districts.xls, and the tribe.mdb. Write down the path of accessing the Districts. xls file.

A:\SCHOOL\EXAMS\F2\Districts.xls                                                               (2 mks)

19. (a) (i) Explain the meaning of backup                                          (2 mks)

It means making of duplicate copies of data or programs from the hard disk into storage media so that in case the system fails, or originals are corrupted or lost, the data can be reconstructed from the backups.

This is used to protect data from accidental erasure or hardware problems

[the_ad id=”1178″]

(ii) Explain two methods you can use in windows to back up data into a storage device             (2 mks)

• –           Using copy and paste commands on the Edit Menu
• –           Using the send to command on the file menu
• –           Using the backup facility to compress the data into another disk

(b) Identify two reasons why a user needs to know the space available for data storage in the hard disk

• –           To know the amount of data that can be stored in the hard disk
• –           To know how much space is left in the hard disk in case a new programs needs to be installed
• –           To detect the likelihood of a virus infection

20. Name the command one would use to repair cross- linked files in graphical user interface software (  1mk)

• Scandisk

21. (a) Explain the team Disk Defragmenter, and give two advantages of this feature ( 3 mks)

• Disk defragmenter is a tool that is used to re- arrange scattered files & folders on a storage media

[the_ad id=”1178″]

Advantages

• –           Rearranges scattered folders & files on storage media
• –           Reduces the time by the read / write head to locate files or folders on the storage media this speed up access to files & folders, hence, makes files to open more quickly
• –           Consolidates related data close to each other, hence, frees space on the storage media

            (b) Distinguish between disk compressing and disk defragmenting

Compressing is creating more space on a disk by squeezing disk contents (files) into a smaller storage location on the disk.

Defragmenting is rearranging scattered related files/ folders closer to each other on the surface of a storage unit.

22.     Give two reasons why a new disk must be formatted before using it               (2 mks)

• –           To prepare a new disk so that files can be stored on it
• –           To create sectors & tracks for the storage of data
• –           To create/ prepare a new root directory and file allocation tables on the disk
• –           To remove/ delete any existing files or information stored on the disk, if it is no longer needed
• –           To determine the effective storage capacity of the disk, i.e. formatting enables the user to know how much data the disk can hold.
• –           It can also check for bad sectors on the new disk.

23. (a) What is meant by the term ‘disk partitioning’?

It is the process of dividing a large physical disk into 2 or more partitions/ volume

            (b) Give two reasons why the hard disk may be partitioned

• –           To install more than one operating systems on the same disk
• –           For the purposes of backup on the same disk, so that if one partition fails the other will still be working.

[the_ad id=”1178″]

24. A Form four computer student is attempting to print a programming documentation. The printer is not responding to the print command. Explain three possible causes for the anomaly. (3 marks)

• –           The printer may not be installed.
• –           The printer may not have been set as the default printer.
• –           The data interface cable to the printer could be loose. Make sure it is firm at the ports.
• –           The printer could still be off. Switch it on, and it will start printing.
• –           The wrong printer could have been selected. Select the right printer in the print dialog box and send the print job again.

25. State two purposes of the recycle bin. (2 marks)

• –           Contains the files and folders that have been deleted.
• –           Can be used to restore files & folders accidentally deleted from the computer.

[the_ad id=”1178″]

MORE NOTES

JOIN US ON TELEGRAM