Numeric

Question 1 Solve: $10 + 10 \times 100 \div 10$ 200 110 10 20 110 Answer: Explanation: According to the BODMAS rule, division is performed first: $100 \div 10 = 10$. Next, we perform multiplication: $10 \times 10 = 100$. Finally, the addition is performed: $10 + 100 = 110$. Question 2 Solve: $10 + 10 \div 100 \times 10$ 2 10 1001/100 11 11 ...
Post a Comment

OPERATING SYSTEM (OS)

OPERATING SYSTEM (OS)

1. Introduction and Definitions

An Operating System (OS) is a fundamental part of a computer that controls and manages its overall operations.

Key Definitions:

  • An operating system is a well-organized set of special software programs that regulates all computer activities.
  • It acts as an interface (communication medium) between the human user, application software, and the computer hardware.
  • It monitors the computer's resources, launches other programs when needed, and ensures successful data processing by issuing instructions to various computer components.

Important Facts:

  • Resource Manager: The OS acts as a resource manager to ensure the optimal utilization of hardware capabilities.
  • User Interface: It provides an easy-to-use interface, making computer operations simple for the user.
  • System Logging: The OS maintains logs of users, tracking their activities and the amount of time they spend working on the computer.

2. Main Functions of an Operating System

The OS plays a vital role in the successful operation of a computer. Its core functions are divided into four main categories:

  • Processing Management:
    • Manages the Central Processing Unit (CPU).
    • Executes programs sequentially and divides CPU time among all active programs.
  • Memory Management:
    • Essential for the successful execution of programs.
    • Reserves specific spaces in the computer's memory and allocates different memory locations to various programs.
    • Temporarily stores data and information in designated memory locations during Input/Output operations.
  • Input-Output (I/O) Device Management:
    • Reads data from input units to appropriate memory locations and sends processed results from memory to output units.
    • The programmer only needs to specify what data to input or output; the OS handles the entire underlying execution process.
  • File Management:
    • Organizes files systematically within directories.
    • Responsible for fetching files from secondary memory (storage) and loading them into primary memory during program execution.

3. Types of Operating Systems

Operating systems are classified based on their processing capabilities, user interactions, and specific use cases.

A. Based on User and Task Handling

  • Single User OS: Allows only one user to work at a time. It is the most commonly used type of OS (e.g., Windows 95, Windows NT, Windows 2000).
  • Multi User OS: Allows multiple users to work simultaneously while balancing resources. It ensures that one user's system issues do not impact other users (e.g., UNIX, VMS).
  • Single Tasking OS: Can only run one program at a time (e.g., Palm computer OS).
  • Multi Tasking OS: Can execute multiple tasks simultaneously, allowing users to easily switch between them. It is further divided into two types:
    1. Preemptive OS: Distributes computation time among tasks based on predefined criteria. It can halt an ongoing task to start a new one (e.g., OS/2, Windows 95/NT).
    2. Cooperative Multi Tasking OS: A simpler form where a program uses the CPU for as long as it needs. If idle, it temporarily yields CPU access to another program (e.g., Mac OS, MS-Windows 3.x).

B. Based on Processing Methods

  • Batch Processing OS: Groups similar tasks into a "batch" and executes them together using batch monitor software. It requires no user intervention and does not need time management. Mainly used for numerical analysis, bill printing, and payroll.
  • Time Sharing OS: Allows multiple users or programs to share computer resources simultaneously.
    • Time Slice/Quantum: The OS allocates a tiny fraction of time (time slice) to each user/program.
    • The switching happens so fast that every user feels they are the sole user of the computer (e.g., Mainframe computers).
    • Swapping: Programs are moved in and out of main memory based on their time slices. If a program exceeds its time slice, it is paused, and the next program is executed.
  • Real Time OS (RTOS): A specialized multitasking OS used for real-time applications with strict deadlines. Delays are unacceptable, as the output of one program often serves as the input for another (e.g., Auto Pilot mechanism in aircraft). It is further divided into two parts.

4. Quick Classification & Comparison Table

Operating System Type Key Characteristic Ideal Use Case / Examples
Batch Processing Groups similar tasks; no user intervention required. Payroll, Bill printing, Numerical Analysis.
Single-User Restricts system to one active user at a time. Standard personal computers (Win 95/2000).
Multi-User Multiple users work simultaneously; isolated user environments. Enterprise servers (UNIX, VMS).
Single-Tasking Runs exactly one program at any given time. Basic handhelds (Palm OS).
Multi-Tasking Runs multiple programs; allows seamless task switching. Modern desktops (Preemptive and Cooperative).
Time-Sharing Uses "Time Slicing" / "Swapping"; creates illusion of sole usage. Mainframe computers.
Real-Time (RTOS) Strict deadlines; zero delay tolerance. Aircraft Auto-Pilot.

 

5. Real-Time Operating System (RTOS) 

Real-Time Operating Systems are designed to handle critical tasks without delay. They are classified into two main categories:

  • Hard Real-Time System: Guarantees that critical tasks are completed perfectly on time. If the task is not completed on time, the execution of the program completely fails.
    • Examples: Air traffic control systems, Pacemakers.
  • Soft Real-Time System: A deadline is provided for the task, but if the execution finishes slightly before or after the deadline, the system does not fail.

6. Some Important Computer Operating Systems

Below is a breakdown of widely used computer operating systems:

  • UNIX:
    • Type: Multi-tasking and Multi-user OS.
    • History: Developed in 1969 at AT&T Bell Labs. Initially written in Assembly language, but rewritten in C language in 1973.
    • Key Features: Full name is Uniplexed Information and Computing System. Mostly used for servers and workstations. Data management is handled by the Kernel. Though difficult to install and set up, it offers exceptionally high computer performance.
  • LINUX:
    • History: Developed in 1991 by Linus Torvalds.
    • Key Features: Based on UNIX and widely used for servers. It is Open-Source software and can run on all types of computers.
  • SOLARIS:
    • History: Developed by Sun Microsystems in 1993, and acquired by Oracle Corporation in 2010 (now known as Oracle Solaris).
    • Key Features: Highly suited for system management and network-related tasks.
  • BOSS (Bharat Operating System Solutions):
    • History: Developed by C-DAC (Centre for Development of Advanced Computing) specifically for use in the Indian region.
    • Key Features: It is Open-Source software. Its latest version is GNU/Linux Version 5.0.
  • MS WINDOWS:
    • History: Developed by Microsoft.
    • Key Features: It is a Graphical User Interface (GUI) OS, making it extremely user-friendly and easy to operate. Popular versions include Windows 95, 98, XP, and Vista.

7. Booting

Booting is the process of starting or restarting a computer. During this process, the Operating System is loaded from the Hard Disk into the computer's RAM (Main Memory).

Types of Booting:

  1. Cold Booting: The process of turning on a computer that is completely powered off.
  2. Warm Booting: The process of restarting a computer that is already turned on.

8. Mobile Operating Systems

Operating systems designed specifically to operate and control the features of smartphones, tablets, and digital mobile devices are called Mobile OS.

  • Android: Introduced by Google in 2007. It is a Linux-based OS primarily designed for touch-screen devices. (Note: A widely known version mentioned is KitKat, introduced in Jan 2014).
  • Symbian: An open-source OS introduced by Symbian Ltd. Widely used in phone sets by companies like Motorola, Sony, Nokia, and Samsung.
  • iOS: A highly popular OS developed by Apple Inc. Exclusively used in Apple devices like the iPhone, iPad, and iPod.
  • Blackberry: Considered the most secure operating system. Used by the Blackberry company for its phones, supporting WAP 1.2. (Latest version mentioned: Blackberry 10).

9. In-Depth: MS-DOS & Command Line Interface

A. MS-DOS (Microsoft Disk Operating System)

  • History: Originally called 86-DOS. In July 1981, Microsoft purchased the rights from IBM, made essential changes (like updating file directory structures), and renamed it MS-DOS.
  • Features: It is a Single-User, Non-Graphical (Command Line) OS. It is not user-friendly because users must memorize specific commands.
  • Primary Functions: Creating new files, deleting old files, renaming files, and creating lists of all files.

B. Command Line Interface (CLI) / Character User Interface (CUI)

  • CLI allows users to interact with the computer/software exclusively through typed text instructions (commands).
  • Input and Output happen entirely in text format, without graphical elements.

C. Structure of DOS

DOS requires four main programs to establish coordination between the OS and the computer hardware:

  1. Boot Record: The main MS-DOS program that loads the OS into main memory.
  2. IOS-SYS (Input/Output System): Provides the interface between the software programs and the hardware.
  3. MSDOS.SYS: A set of program routines and data tables that serve high-level application programs.
  4. Command.Com: Provides a set of commands to the user, facilitating file management and other tasks.

D. Configuring DOS

  • Config.Sys: Adjusts the computer system environment according to specific commands.
  • Autoexec.Bat: A file that executes automatically in the command line the moment the system is turned on.

10. Important File Extensions in DOS

Extension Description
.exe Executable files
.com Command files
.bat Batch files
.doc Document files
.txt Text files
.prg Program files
.ovr Over lays
.sys System files

 

11. MS-DOS Commands

In MS-DOS, commands are instructions given to the computer to perform specific tasks. They are broadly classified into two categories: Internal and External commands.

A. Internal Commands

  • Definition: These are built-in commands that are pre-stored in the main MS-DOS processing file called command.com.
  • Function: They allow users to view root directories and files directly.
  • Syntax Example: DIR>\:C .
  • Examples: DATE, TIME, VER, VOL, DIR, COPY.

B. External Commands

  • Definition: These commands are not available in the computer's main memory by default.
  • Storage: They are stored on the disk as separate, standalone program files.
  • Examples: CHKDSK, Tree, Attrib, Diskcopy.

12. Important MS-DOS Commands and Their Uses

Here is a comprehensive quick-revision table of essential MS-DOS commands and their primary functions.

Command Purpose / Function
DATE To view and change the date set in the PC.
TIME To view and change the time set in the PC.
CLS To clear the information displayed on the screen.
DIR To view the list of files and sub-directories included in a directory.
CD To view the current directory.
COPY To make a copy of a file.
REN To change (rename) the name of a file.
DEL To remove/delete a file from a disk or floppy.
MD To create a new directory or sub-directory.
RD To remove an existing directory.
TYPE To view the contents inside a file.
FORMAT To prepare a new or old floppy/disk to work on MS-DOS.
PATH To find the path of an executable directory or file.
EDIT To create or correct a file made of simple text, numbers, and special symbols.
PRINT To print a file.
XCOPY To copy a directory along with its sub-directories and their files.
ERASE To remove one or more files.
VER To view the version information of the Operating System.
SORT To organize/change the data of a file into ascending or descending order.
CHKDSK To check the position and status of the active disk.
DISKCOPY To completely copy the contents of one disk to another target disk.
MOVE To shift a file from one disk/path to another disk/path.

13. Must-Know Computer Terminology (Key Concepts)

Understanding the following concepts is crucial for operating system fundamentals:

  • Open Source Software:
    • Software where the Source Code is available to everyone either for free or for a very small fee.
    • Users and developers can easily make modifications to the source code to improve or customize it.
  • Utility Software:
    • Programs that assist the Operating System by handling maintenance tasks that the OS does not manage directly.
    • Examples: Disk Compression and Disk Defragmentation tools.
  • Kernel:
    • The core, central part of the Operating System.
    • Function: It is responsible for directly commanding and directing the tasks happening inside the CPU.

SUMMARY / REVISION NOTES (Quick Takeaways)

  • Definition: OS = Software interface between User and Hardware.
  • Core Functions (The 4 M's of Management):
    1. Process Management: CPU scheduling.
    2. Memory Management: Primary storage allocation.
    3. I/O Management: Handling peripherals and data flow.
    4. File Management: Directory organization and storage fetching.
  • Key Vocabulary to Remember:
    • Interface: The communication bridge (OS) between hardware and user.
    • Time Slice / Quantum: The tiny allocated timeframe given to a process in Time-Sharing OS.
    • Swapping: Moving programs back and forth between main memory and secondary storage in Time-Sharing.
    • Preemptive: An OS that can forcibly pause a running task to start another based on priority/time.
    • Cooperative: An OS where programs voluntarily yield control of the CPU when idle.
  • Exam Tip: Be able to differentiate between Time Sharing (focuses on fair resource division among users via swapping) and Real-Time OS (focuses on strict, absolute deadlines for mission-critical tasks like auto-pilots).
  • UNIX vs LINUX: UNIX was born in 1969 at Bell Labs (C language, data managed by Kernel). Linux is the 1991 open-source derivative of UNIX created by Linus Torvalds.
  • Indian OS: BOSS (Bharat Operating System Solutions) was made by C-DAC for India.
  • GUI vs CLI:
    • MS Windows uses GUI (Graphical User Interface) making it user-friendly.
    • MS DOS uses CLI/CUI (Command Line / Character User Interface) relying entirely on typed text commands, lacking user-friendliness.
  • Booting Types: Cold = Starting from power off. Warm = Restarting.
  • Mobile OS Giants: Google makes Android (Linux-based), Apple makes iOS, and Blackberry is known for high security.
  • DOS Structure Memory Trick (BIMC):
    • Boot Record (Loads OS)
    • IOS-SYS (Hardware Interface)
    • MSDOS.SYS (Data tables)
    • Command.Com (File management instructions)
  • Internal vs. External Commands:
    • Internal: Built into command.com (e.g., DIR, COPY, DATE, TIME).
    • External: Stored separately on the disk (e.g., CHKDSK, Diskcopy, Tree).
  • File & Directory Management Trick:
    • MD = Make Directory.
    • RD = Remove Directory.
    • CD = Current Directory.
    • DEL vs ERASE: Both delete files, but ERASE is often used for multiple files.
    • COPY vs XCOPY: COPY handles individual files, while XCOPY is powerful enough to copy entire directories and their contents.
  • System Utilities to Remember:
    • FORMAT: Preps a disk for use.
    • CHKDSK: Checks disk health/status.
    • DISKCOPY: Clones one disk to another.
  • Core Concepts to Memorize:
    • Kernel: The OS "brain" that bosses the CPU around.
    • Open Source: Free to modify source code.
    • Utility Software: Helper programs for system maintenance (like defragmentation).

Comments

Post a Comment

Popular posts from this blog

Motion

Image
MOTION 1. Introduction In physics, the branch of science that deals with the study of objects in the condition of rest or motion is known as mechanics . Mechanics is further divided into statics, which studies objects at rest, and kinematics and dynamics , which study objects in motion. Kinematics deals with the study of the motion of objects without considering the cause of the motion, whereas dynamics considers the cause of the motion. 1.1 Rest and Motion An object is said to be at rest if its position does not change with respect to its surroundings with the passage of time. For example, the chairs and blackboards in a classroom are at rest with respect to the students. Conversely, if the location of an object changes continuously with time relative to its surroundings or an observer, the object is said to be in motion. Rest and motion are relative terms; there is no such thing as absolute motion or absolute rest. For example, passengers sitting inside a moving bus appear...
Read more

Counting Figures

Image
 Logical Reasoning: Counting Figures (आकृतियों की गणना) Counting figures requires systematic categorization (e.g., counting single/small shapes first, then compound shapes formed by 2, 3, or more parts, and finally the largest overall shape). Below are all 60 bilingually transcribed questions from the exam sheets with their verified answers and detailed explanations. Q.1 Question: How many triangles are there in the following figure? दिये गये चित्र में कितने त्रिभुज है? Options: (a) 11 (b) 13 (c) 9 (d) 15 Answer: (b) 13 Explanation: The figure is a large triangle divided into smaller symmetric triangular compartments with $n = 3$ divisions along the base. Formula Method: For a symmetric triangle with $n$ levels: $$\text{Total Triangles} = \text{Integer part of } \frac{1}{8}n(n+2)(2n+1)$$ For $n = 3$ : $$\text{Total} = \left\lfloor \frac{1}{8} \times 3 \times 5 \times 7 \right\rfloor = \left\lfloor \frac{105}{8} \right\rfloor = \lfloor 13.125 \rfloor = 13$$ Manual Counting Me...
Read more
Question 1 If $\div$ stands for subtraction, $+$ stands for multiplication, $-$ stands for division, and $\times$ stands for addition, then which one of the following equations is correct? / यदि '$\div$' का अर्थ है '$-$', '+' का अर्थ है '$\times$', '$-$' का अर्थ है '$\div$' और '$\times$' का अर्थ है '+' तो निम्नलिखित में से कौन-सा समीकरण सही है? 19 + 5 - 4 \times 2 \div 4 = 1 19 \times 5 - 4 \div 2 + 4 = 16 19 \div 5 + 4 - 2 \times 4 = 13 19 \div 5 + 4 + 2 \div 4 = 20 19 \div 5 + 4 - 2 \times 4 = 13 Answer: Explanation: To solve this, substitute the original operators with ...
Read more