Chapter 3: Operating Systems

What to remember

• An operating system (OS) is system software that manages hardware, runs programs and gives the user an interface. Windows is a GUI-based OS from Microsoft; Linux is open source and is a UNIX-like OS; MS-DOS is a command-line OS.
• Know the file and folder basics: file extensions, Recycle Bin, Task Manager, Control Panel and the main DOS commands (DIR, CD, MD, COPY, DEL, CLS, REN).
• Shortcut keys are frequently asked: Ctrl+C copy, Ctrl+X cut, Ctrl+V paste, Ctrl+Z undo, Alt+Tab switch window, Windows key + D show desktop.

Operating system basics

An operating system sits between the user and the hardware. When the computer starts, the boot process loads the OS into RAM. Without an OS, a computer cannot run application programs.

Main functions of an OS:

• Process management: decides which program gets the CPU and for how long.
• Memory management: gives and takes back RAM for programs.
• File management: creates, stores, names, finds and deletes files and folders.
• Device management: controls input and output devices through programs called drivers.
• Security: user accounts, passwords and permissions.
• User interface: a way for the user to give commands.

Types of OS by use:

• Single-user: one user at a time, such as MS-DOS.
• Multi-user: many users share one computer, such as UNIX and Linux.
• Multitasking: runs several programs at once, such as Windows.
• Batch: jobs are collected and run together, with no user interaction.
• Real-time (RTOS): gives results within a fixed time, used in missiles, medical devices and industrial control.
• Time-sharing: the CPU time is divided in small slices among many users.
• Mobile OS: Android and iOS.

Interfaces: a CLI (Command Line Interface) needs typed commands, as in DOS. A GUI (Graphical User Interface) uses windows, icons, menus and a pointer, as in Windows. The kernel is the core of the OS that talks to the hardware. The shell is the part that takes the user's commands and passes them to the kernel.

Windows

Windows is a multitasking GUI operating system made by Microsoft. Its first big success came with Windows 3.0 (1990); Windows 95 introduced the Start button and taskbar. Later versions include Windows XP, 7, 8, 10 and 11.

Key parts of the Windows screen:

• Desktop: the main screen where icons are placed.
• Icon: a small picture for a file, folder or program.
• Taskbar: the strip at the bottom that shows the Start button, running programs and the notification area.
• Start menu: opens programs, settings and the power options.
• Recycle Bin: holds deleted files. Files can be restored from here until it is emptied. Pressing Shift+Delete deletes a file directly without sending it to the Recycle Bin.
• Control Panel and Settings: change system options such as display, users and uninstalling programs.
• Task Manager: shows running programs and processes and lets you end a program that has stopped responding. It opens directly with Ctrl+Shift+Esc, or from the screen shown by Ctrl+Alt+Delete.
• File Explorer (Windows Explorer): the tool for browsing files and folders.
• Notepad: a simple text editor. WordPad and Paint are other built-in programs.

Windows has window controls: minimise, maximise or restore, and close. A dialog box asks the user for choices. A folder holds files and other folders. A path is the address of a file, such as C:\Users\Ravi\Documents\letter.docx. The drive letters C: and D: name disk partitions; A: and B: were used for floppy disks.

Linux and UNIX basics

UNIX is a powerful multi-user, multitasking OS first created at Bell Labs. Linux is a free and open source UNIX-like kernel created by Linus Torvalds. Anyone can see, change and share its source code. Linux comes in many flavours called distributions, such as Ubuntu, Fedora, Debian and Red Hat. Android is also built on the Linux kernel. Linux is widely used on servers because it is stable and secure. Its mascot is a penguin called Tux. Open source means the source code is free for all to use and modify.

File system: Linux has a single tree with the root directory shown as "/". Users' home folders are inside /home. Names are case sensitive, so "File" and "file" are different.

Common Linux commands:

DOS commands

MS-DOS (Microsoft Disk Operating System) is a single-user, single-tasking, command-line OS. The prompt looks like C:\>. Commands are of two kinds. Internal commands are built into the command interpreter (COMMAND.COM) and are always available. External commands are separate program files that must be present on the disk.

Wildcards: * stands for any group of characters, and ? stands for one character. For example, DIR *.TXT lists all text files. A batch file has the extension .BAT and holds a list of DOS commands. AUTOEXEC.BAT and CONFIG.SYS are start-up files of DOS.

File management

A file is a named collection of data stored on a disk. The file name has two parts: the name and the extension, separated by a dot. The extension tells the type.

Basic operations are create, open, save, copy, move, rename, delete and search. Copy leaves the original in place; cut and paste moves it. Rename can be done with F2. A shortcut is a link to a file placed elsewhere, such as on the desktop. Properties show size, type and date. Compression (ZIP) reduces file size. Defragmentation arranges scattered pieces of files on an HDD to speed it up. Formatting prepares a disk with a file system, such as NTFS or FAT32; it erases data. NTFS is the modern Windows file system.

Shortcut keys

Exam traps

• DOS is command-line and single-tasking; Windows is GUI and multitasking.
• Shift+Delete skips the Recycle Bin; plain Delete sends the file there.
• Cut and paste moves a file; copy and paste keeps the original.
• Linux is open source and free; Windows is proprietary.
• Linux file names are case sensitive; Windows file names are not.
• DIR, COPY, DEL, REN and CLS are internal commands; FORMAT, XCOPY and CHKDSK are external.
• The kernel talks to hardware; the shell talks to the user.
• Ctrl+Y is redo; Ctrl+Z is undo. Alt+F4 closes a window, but Ctrl+F4 closes only the document inside a program.
• Linus Torvalds made Linux; he did not make UNIX.

One-liners

• 1. An OS manages hardware and software resources of a computer.
• 2. Linux was created by Linus Torvalds.
• 3. MS-DOS is a single-user, command-line OS.
• 4. The Recycle Bin keeps deleted files until it is emptied.
• 5. Task Manager can end a program that is not responding.
• 6. The extension of a Word file is .docx and of Excel is .xlsx.
• 7. In DOS, CLS clears the screen.
• 8. The wildcard * stands for any number of characters.
• 9. Alt+Tab switches between open programs.
• 10. Android is built on the Linux kernel.
• 11. The root directory in Linux is written as "/".
• 12. A driver is a program that lets the OS control a device.

Practice questions

1. Which of the following is system software?

   1. Media player
   2. MS Word
   3. Tally
   4. Operating system
   Answer

   D. Operating system

   An OS manages the computer and is system software.

2. Who created the Linux kernel?

   1. Dennis Ritchie
   2. Bill Gates
   3. Linus Torvalds
   4. Steve Jobs
   Answer

   C. Linus Torvalds

   Linus Torvalds released Linux as a free UNIX-like kernel.

3. MS-DOS is an example of a

   1. graphical OS
   2. mobile OS
   3. command line interface OS
   4. real-time OS only
   Answer

   C. command line interface OS

   DOS needs typed commands.

4. Which keys copy the selected item?

   1. Ctrl+Z
   2. Ctrl+C
   3. Ctrl+X
   4. Ctrl+V
   Answer

   B. Ctrl+C

   Ctrl+C copies; Ctrl+V pastes.

5. Which shortcut undoes the last action?

   1. Ctrl+U
   2. Ctrl+D
   3. Ctrl+Y
   4. Ctrl+Z
   Answer

   D. Ctrl+Z

   Ctrl+Z is undo; Ctrl+Y is redo.

6. Which shortcut switches between open windows?

   1. Ctrl+Tab
   2. Alt+Tab
   3. Shift+Tab
   4. Alt+Esc only
   Answer

   B. Alt+Tab

   Alt+Tab cycles through open programs.

7. Which DOS command clears the screen?

   1. VER
   2. DEL
   3. CLS
   4. DIR
   Answer

   C. CLS

   CLS means clear screen.

8. Which DOS command lists files and folders?

   1. MD
   2. TYPE
   3. REN
   4. DIR
   Answer

   D. DIR

   DIR shows the directory listing.

9. The extension of a Microsoft Word file is

   1. docx
   2. txt
   3. pptx
   4. xlsx
   Answer

   A. docx

   Word uses .docx.

10. Deleted files in Windows first go to the

    1. Control Panel
    2. Recycle Bin
    3. Task Manager
    4. Clipboard
    Answer

    B. Recycle Bin

    The Recycle Bin allows restoring deleted files.

11. Which program is used to end a program that is not responding?

    1. Recycle Bin
    2. Notepad
    3. Task Manager
    4. Paint
    Answer

    C. Task Manager

    Task Manager lists processes and lets you end a task.

12. The strip at the bottom of the Windows screen is called the

    1. Status bar
    2. Menu bar
    3. Title bar
    4. Taskbar
    Answer

    D. Taskbar

    The taskbar holds the Start button and running programs.

13. Linux is an example of

    1. open source software
    2. proprietary software
    3. shareware only
    4. firmware
    Answer

    A. open source software

    Its source code is free to view and change.

14. Which of the following is a Linux distribution?

    1. Paint
    2. Ubuntu
    3. Windows XP
    4. MS-DOS
    Answer

    B. Ubuntu

    Ubuntu, Fedora and Debian are distributions.

15. Which key combination permanently deletes a file without using the Recycle Bin?

    1. Delete
    2. Ctrl+Delete
    3. Shift+Delete
    4. Alt+Delete
    Answer

    C. Shift+Delete

    Shift+Delete bypasses the Recycle Bin.

16. Which function key renames a selected file in Windows?

    1. F12
    2. F1
    3. F5
    4. F2
    Answer

    D. F2

    F2 starts rename; F5 refreshes.

17. Which Linux command shows the present working directory?

    1. pwd
    2. ls
    3. cd
    4. cat
    Answer

    A. pwd

    pwd means print working directory.

18. Which Linux command lists files in a directory?

    1. cp
    2. ls
    3. rm
    4. mv
    Answer

    B. ls

    ls lists directory content.

19. Which of the following is an external DOS command?

    1. COPY
    2. DIR
    3. FORMAT
    4. CLS
    Answer

    C. FORMAT

    FORMAT is a separate program file, not built into COMMAND.COM.

20. Which of the following is an internal DOS command?

    1. REN
    2. CHKDSK
    3. TREE
    4. XCOPY
    Answer

    A. REN

    REN is built into COMMAND.COM.

21. In DOS, the wildcard symbol that stands for any group of characters is

    1. #
    2. *
    3. ?
    4. $
    Answer

    B. *

    * matches many characters; ? matches exactly one.

22. The core part of an OS that directly controls hardware is the

    1. shell
    2. driver
    3. compiler
    4. kernel
    Answer

    D. kernel

    The kernel is the heart of the OS.

23. The part of an OS that accepts and interprets user commands is the

    1. shell
    2. driver
    3. kernel
    4. BIOS
    Answer

    A. shell

    The shell passes commands to the kernel.

24. An OS in which many programs run at the same time is called

    1. single tasking
    2. batch only
    3. simplex
    4. multitasking
    Answer

    D. multitasking

    Windows is a multitasking OS.

25. An OS that must respond within a fixed time limit is a

    1. real-time OS
    2. batch OS
    3. single-user OS
    4. network OS only
    Answer

    A. real-time OS

    Used in control systems and medical devices.

26. A program that lets the OS control a hardware device is called a

    1. assembler
    2. driver
    3. browser
    4. compiler
    Answer

    B. driver

    Device drivers connect the OS to hardware.

27. Which file extension denotes a program that can be run directly?

    1. jpg
    2. pdf
    3. exe
    4. txt
    Answer

    C. exe

    .exe is an executable file.

28. Which shortcut opens Task Manager directly?

    1. Ctrl+Esc
    2. Ctrl+Shift+Esc
    3. Ctrl+Alt+Tab
    4. Alt+F4
    Answer

    B. Ctrl+Shift+Esc

    Ctrl+Shift+Esc opens Task Manager.

29. Which shortcut shows the desktop in Windows?

    1. Windows key + E
    2. Windows key + L
    3. Windows key + D
    4. Windows key + R
    Answer

    C. Windows key + D

    Win+D minimises all windows. Win+E opens File Explorer; Win+L locks.

30. Defragmentation is done to

    1. delete old files
    2. compress files
    3. install drivers
    4. arrange scattered file pieces on a disk
    Answer

    D. arrange scattered file pieces on a disk

    It improves access speed on an HDD.

31. The file system commonly used by modern Windows is

    1. EXT only
    2. HFS
    3. NTFS
    4. ISO
    Answer

    C. NTFS

    NTFS is the standard Windows file system.

32. Which command creates a new folder in DOS?

    1. CD
    2. MD
    3. DIR
    4. RD
    Answer

    B. MD

    MD means make directory; RD removes one.

33. In Linux, which command is used to change file permissions?

    1. chmod
    2. chown only
    3. mkdir
    4. sudo
    Answer

    A. chmod

    chmod changes read, write and execute permissions.

34. The root directory of a Linux file system is written as

    1. \
    2. C:\
    3. ~
    4. /
    Answer

    D. /

    Linux has one tree starting at /.

35. Which of the following is a batch file extension in DOS?

    1. bas
    2. bat
    3. bak
    4. bin
    Answer

    B. bat

    Batch files carry the .BAT extension.

36. The mobile operating system Android is based on the

    1. Symbian kernel
    2. UNIX Windows kernel
    3. DOS kernel
    4. Linux kernel
    Answer

    D. Linux kernel

    Android is built on the Linux kernel.

37. Statements: 1. Linux file names are case sensitive. 2. Windows is open source. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Windows is proprietary; Linux is open source.

38. Statements: 1. DIR is an internal DOS command. 2. FORMAT is an internal DOS command. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    FORMAT is an external command.

39. Statements: 1. Cut and paste moves a file. 2. Copy and paste keeps the original. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both describe the operations correctly.

40. Statements: 1. Ctrl+Y is undo. 2. Ctrl+Z is undo. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Ctrl+Z is undo; Ctrl+Y is redo.

41. Statements: 1. The kernel interacts with hardware. 2. MS-DOS is multi-user. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    MS-DOS is single-user.

42. Statements: 1. A GUI uses icons and windows. 2. A CLI needs typed commands. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    These are the standard descriptions.

43. Statements: 1. Alt+F4 closes the active window. 2. Shift+Delete sends a file to the Recycle Bin. Which is/are correct?

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Shift+Delete deletes permanently.

44. Match the pair: which pair is correct?

    1. TYPE - deletes a file
    2. VER - renames a file
    3. TREE - clears the screen
    4. XCOPY - copies folders with files
    Answer

    D. XCOPY - copies folders with files

    TYPE shows file contents; VER shows version; TREE shows folder structure.

45. Which Windows key combination locks the computer?

    1. Alt+F4
    2. Windows key + D
    3. Windows key + E
    4. Windows key + L
    Answer

    D. Windows key + L

    Win+L locks the screen.