Linux OS and CLI

Linux is a popular open-source operating system kernel that serves as the foundation for a variety of Unix-like operating systems. These operating systems are often referred to as Linux distributions or simply "distros." The kernel was created by Linus Torvalds in 1991 and has since been adopted and adapted by a large community of developers worldwide.

Key features of Linux and Linux distributions include:

1. Open Source: Linux is distributed under the GNU General Public License (GPL), which means its source code is freely available to the public. Users can view, modify, and distribute their own versions of the operating system.
2. Multitasking: Linux supports multitasking, allowing multiple processes to run simultaneously. This is essential for server environments and other scenarios where many tasks need to be performed concurrently.
3. Multiuser: Linux is designed to support multiple users simultaneously. Each user can have their own account and settings, ensuring a secure and personalized experience.
4. Stability and Reliability: Linux is known for its stability and reliability. It is often used in critical environments such as servers, where uptime is crucial.
5. Security: Linux has a strong security model, and it benefits from the open-source community's scrutiny, which helps identify and patch security vulnerabilities quickly.
6. Command-Line Interface (CLI): Linux provides a powerful command-line interface, allowing users to interact with the system using text commands. This is a powerful tool for system administrators and power users.
7. Graphical User Interface (GUI): While Linux can be used entirely from the command line, most distributions also offer graphical user interfaces, making it accessible to a broader range of users.
8. Package Management: Linux distributions typically use package management systems that simplify the installation, update, and removal of software packages. Common package management tools include APT (Advanced Package Tool), YUM (Yellowdog Updater Modified), and others.
9. Diversity of Distributions: There are numerous Linux distributions, each with its own goals, target audience, and package management systems. Examples include Ubuntu, Fedora, Debian, CentOS, Arch Linux, and many more.
10. Kernel Customization: Users can compile and customize the Linux kernel to suit their specific hardware and performance requirements.

Linux is widely used in various environments, including desktops, servers, embedded systems, and supercomputers. It powers a significant portion of the internet infrastructure and is the operating system of choice for many developers and IT professionals.

Linux desktop

A Linux desktop typically refers to a Linux-based operating system configured with a graphical user interface (GUI) that provides a desktop environment. Linux desktop environments offer a user-friendly interface and various tools to interact with the system. There are several popular Linux desktop environments, each with its own look, feel, and set of features. Some of the notable desktop environments include:

GNOME: Known for its modern and streamlined design, GNOME is the default desktop environment for several major Linux distributions like Ubuntu. It features a clean user interface with a focus on simplicity and ease of use.

KDE Plasma: KDE Plasma is another widely used desktop environment, offering a more feature-rich and customizable experience. It provides a traditional desktop layout but allows users to customize almost every aspect of their desktop environment.

Linux commands:  Linux commands are text-based instructions used in a terminal or console to perform various tasks on a Linux-based operating system. Here are some commonly used Linux commands:

1. ls: List files and directories in the current directory.
2. cp: Copy files or directories.
3. mv: Move or rename files or directories.
4. rm: Remove files or directories.
5. mkdir: Create a new directory.
6. rmdir: Remove an empty directory.
7. touch: Create an empty file or update the timestamp of an existing file.
8. cat: Concatenate and display the content of files.
9. less or more: Display the content of a file one screen at a time.
10. head and tail: Display the beginning or end of a file.
11. chmod: Change file permissions.
12. chown: Change file owner and group.
13. file: Determine the type of a file.
14. find: Search for files and directories based on various criteria.
15. grep: Search for a pattern in files.
16. wc: Count the number of lines, words, and characters in a file.
17. diff: Compare two files line by line.
18. ln: Create hard or symbolic (soft) links to files.
19. stat: Display detailed information about a file.
20. du: Display file and directory space usage.

Here are some Linux commands that are not directly related to files and directories:

1. pwd: Print the current working directory.
2. echo: Display a message or enable/disable the echoing of commands.
3. date: Display the current date and time.
4. cal: Display a calendar.
5. history: Display command history.
6. hostname: Display or set the system's hostname.
7. uptime: Display how long the system has been running.
8. whoami: Display the current username.
9. ps: Display information about running processes.
10. kill: Terminate a process.
11. top: Display real-time system statistics and a list of processes.
12. df: Display disk space usage.
13. free: Display amount of free and used system memory.
14. uname: Display system information.
15. ifconfig or ip: Display network configuration.
16. ping: Send ICMP echo requests to test network connectivity.
17. traceroute or tracepath: Display the route that packets take to reach a network host.
18. man: Display the manual or help page for a command.
19. sudo: Execute a command with superuser privileges.
20. reboot and shutdown: Restart or shut down the system.

NUMBER SYSTEM

NUMBER SYSTEM

The technique to represent and work with numbers is called Number system. Decimal number system is the most common number system. Other popular number systems include binary number system, octal number system, hexadecimal number system, etc.

Binary Number System:- The number system having just these two digits 0 and 1 is called Binary number system. Each binary digit is also called a Bit. Binary number system is also positional value system, where each digit has a value expressed in powers of 2, as displayed here. The binary number system, also known as base-2, is a numeral system that uses only two digits, 0 and 1. It is the most fundamental numeral system used in digital computers and digital systems. In binary, each digit is referred to as a "bit" (a contraction of "binary digit"). The position of each bit in a binary number represents a power of 2. 

Decimal Number System:- The decimal number system, also known as the base-10 system, is the standard system for denoting integer and non-integer numbers. It uses ten digits from 0 to 9 to represent numbers. The position of each digit in a decimal number is a power of 10. The rightmost digit represents the units, the next digit to the left represents tens, then hundreds, and so on. Each digit's value is multiplied by the corresponding power of 10.

Octal Number System:-The octal number system, also known as base-8, is a numeral system that uses eight digits: 0, 1, 2, 3, 4, 5, 6, and 7. It is a positional number system, just like the decimal system (base-10) and binary system (base-2). Each digit in an octal number represents a power of 8.

Octal Numbers System Table

We use only 3 bits to represent Octal Numbers. Each group will have a distinct value between 000 and 111.

Octal Digital Value	Binary Equivalent
0	000
1	001
2	010
3	011
4	100
5	101
6	110
7	111

Hexadecimal Number System:- The hexadecimal number system, often abbreviated as hex, is a base-16 numeral system. It uses sixteen digits: 0-9 and the letters A-F, where A represents 10, B is 11, C is 12, D is 13, E is 14, and F is 15 in decimal. Hexadecimal is a positional numeral system, similar to the decimal (base-10) and binary (base-2) systems.

Hexadecimal Number System Table

Below is the table of hexadecimal number systems with equivalent values of the binary and decimal number systems.

Decimal Numbers	4-bit Binary Number	Hexadecimal Number
0	0000	0
1	0001	1
2	0010	2
3	0011	3
4	0100	4
5	0101	5
6	0110	6
7	0111	7
8	1000	8
9	1001	9
10	1010	A
11	1011	B
12	1100	C
13	1101	D
14	1110	E
15	1111	F

    CONVERSATION OF NUMBER SYSTEM

Decimal Number System to Other Bases

Earlier we learned about converting other base number systems into a decimal number, Here we will learn how to convert a decimal number into different base numbers. Let us see one by one.

Decimal to Binary

To convert a decimal number into an equivalent binary number we have to divide the original number system by 2 until the quotient is 0, when no more division is possible. The remainder so obtained is counted for the required number in the order of LSB (Least significant bit) to MSB (most significant bit). Let us go through the example.

Example: Convert 2610 into a binary number. Solution: Given 2610 is a decimal number. Divide 26 by 2 26/2 = 13 Remainder →0 (MSB) 13/2 = 6 Remainder →1 6/2 = 3 Remainder →0 3/2 = 1 Remainder →1 ½ = 0 Remainder →1 (LSB) Hence, the equivalent binary number is (11010)2

Decimal to Octal

Here the decimal number is required to be divided by 8 until the quotient is 0. Then, in the same way, we count the remainder from LSB to MSB to get the equivalent octal number.

Example: Convert 6510 into an octal number. Solution: Given 6510 is a decimal number. Divide by 8 65/8 = 8 Remainder →1 (MSB) 8/8 = 1 Remainder →0 ⅛ = 0 Remainder →1 (LSB) Hence, the equivalent octal number is (101)8

Decimal to Hexadecimal

The given decimal number here is divided by 16 to get the equivalent hex. The division of the number continues until we get the quotient 0.

Example: Convert 12710 to a hexadecimal number. Solution: Given 12710 is a decimal number. Divide by 16 127/16 = 7 Remainder →15 7/16 = 0 Remainder → 7 In the hexadecimal number system, alphabet F is considered as 15. Hence, 12710 is equivalent to 7F16

Binary Conversion 

Binary to Decimal Conversion Steps

• First, write the given binary number and count the powers of 2 from right to left (powers starting from 0)
• Now, write each binary digit (right to left) with the corresponding powers of 2 from (right to left), such that first binary digit (MSB) will be multiplied with the greatest power of 2.
• Add all the products in the above step
• The final answer will be the required decimal number

Let us understand this conversion with the help of an example.

Example of Binary to Decimal Conversion:

Convert the binary number (1101)2 into a decimal number.

Solution:

Given binary number = (1101)2

Now, multiplying each digit from MSB to LSB with reducing the power of the base number 2.

1 × 23 + 1 × 22 + 0 × 21 + 1 × 20

= 8 + 4 + 0 + 1

= 13

Thus, the equivalent decimal number for the given binary number (1101)2 is (13)10

Conversion from Binary to Octal

In number system, you will come across different types of numbers such as binary, octal, decimal and hexadecimal. To convert binary numbers to octal numbers, follow the below steps:
Take the given binary number

1. Multiply each digit by 2n-1 where n is the position of the digit from the decimal
2. The resultant is the equivalent decimal number for the given binary number
3. Divide the decimal number by 8
4. Note the remainder
5. Continue the above two steps with the quotient till the quotient is zero
6. Write the remainder in the reverse order
7. The resultant is the required octal number for the given binary number

Binary to Hex Conversion

A binary number has base 2 and consist of only two digits, that are 0 and 1. It has a major use in computer applications.

Hexadecimal numbers are represented by base 16. It uses 0 to 9 digits and for higher numbers, it is represented by English alphabets such as A,B,C,D,E and F.

To convert binary number to hexadecimal is an easy method. We have to group the given binary number in pair of 4 and then find the equivalent hexadecimal number from the below table.

Binary Arithmetic

Binary mathematics refers to mathematical operations performed using the binary number system, which is a base-2 numeral system. In the binary system, numbers are expressed using only the digits 0 and 1. Each digit in a binary number is called a "bit".
Here are some basic concepts and operations in binary mathematics: Binary numbers are made up of only two digits: 0 and 1. In the binary number system, no other numbers can be used except 1 and 0.
1. Binary Addition:
◦ The addition table in binary is as follows
0 + 0 = 0
0 + 1 = 1
1 + 0 = 1
1 + 1 = 10 (move 1 to the next column)
2. Binary Subtraction:
• Similar to decimal subtraction but with the rules of borrowing. The subtraction table in binary is as follows:
0 – 0= 0
1 - 0 = 1
1 - 1 = 0
0 - 1 = 1 (borrow 1 from the next column)
3. Binary Multiplication:
◦ Similar to decimal multiplication but involves multiplying by 0 or 1. The multiplication table in binary is simpler than that in decimal. The rules of binary multiplication are as follows.
0 X 0 = 0
0 X 1 = 0
1 X 0 = 0
1 X 1 = 1
4. Binary Division:
◦ The rules of binary division are as follows.
0 ÷ 0 = undefined
0 ÷ 1 = 0
1 ÷ 0 = undefined
1 ÷ 1 = 1

An operating system (OS) is system software that manages computer hardware, software resources, and provides various services for computer programs. It acts as an intermediary between users and the computer hardware. The primary functions of an operating system include:

1. Process Management: The OS manages processes (programs in execution), including process scheduling, creation, termination, and communication between processes.
2. Memory Management: It allocates and deallocates memory space as needed by different programs and ensures that processes don't interfere with each other's memory.
3. File System Management: The OS provides a file system that organizes and manages data on storage devices, such as hard drives. It includes functions for file creation, deletion, and manipulation.
4. Device Management: The OS manages input and output devices, such as keyboards, printers, and disk drives, by providing device drivers and handling communication between devices and the CPU.
5. Security and Protection: Operating systems implement security measures to protect data and resources from unauthorized access. This includes user authentication, encryption, and access control.
6. User Interface: The OS provides a user interface that can be command-line based or graphical. The user interface allows users to interact with the computer system and its applications.
7. Networking: Many modern operating systems include networking capabilities to enable communication between computers, either in a local network or over the internet.
8. Error Handling: The OS is responsible for detecting and handling errors that may occur during the operation of the computer system.

Common examples of operating systems include:

• Microsoft Windows: A widely used operating system for personal computers.
• MacOS: The operating system for Apple's Macintosh computers.
• Linux: An open-source operating system kernel used by many distributions (e.g., Ubuntu, Fedora) for servers, desktops, and other computing devices.
• Unix: An operating system that has influenced many others, including Linux and MacOS.
• Android: A mobile operating system developed by Google, widely used in smartphones and tablets.

TYPES OF OPERATING SYSTEM

Each operating system has its strengths, weaknesses, and specific use cases, catering to different user needs and preferences. There are several types of operating systems, each designed for specific types of devices and applications. Here are some common types. These categories often overlap, and modern operating systems may incorporate features from multiple types. The choice of the operating system depends on the specific requirements and characteristics of the computing environment in which it will be used.

1. Single User, Single Tasking: Examples: MS-DOS (Microsoft Disk Operating System), early versions of Apple OS.
2. Single User, Multitasking: Allows a single user to run multiple programs simultaneously.
3. Examples: Microsoft Windows (modern versions), MacOS, Linux (desktop distributions).
4. Multi-User: Supports multiple users simultaneously. Examples: Unix, Linux (server distributions), mainframe operating systems like IBM z/OS.
5. Real-Time Operating System (RTOS): Designed for systems that require immediate and predictable responses to events. Examples: VxWorks, QNX, Free RTOS. 
6. Multi-Processing Operating System: Manages multiple processors to provide improved performance. Examples: Linux, Windows Server, Unix variants.
7. Distributed Operating System: Manages a group of independent computers and makes them appear as a single computer. Examples: Google Chrome OS, Amoeba.
8. Network Operating System: Designed to support networked computing. Examples: Novell NetWare, Windows Server (for networking purposes).
9. Mobile Operating System: Designed for mobile devices like smartphones and tablets. Examples: Android, iOS, Harmony OS (used by Huawei).
10. Embedded Operating System: Tailored for specific embedded systems and devices. Examples: VxWorks (used in embedded systems), Embedded Linux, Free RTOS.
11. Real-Time Executive (RTE): A type of RTOS used in embedded systems for real-time applications. Examples: RT Linux, Free RTOS.
12. Server Operating System: Optimized for server hardware and applications. Examples: Windows Server, Linux server distributions (e.g., Ubuntu Server, CentOS).

Microsoft Windows

Microsoft Windows is a widely used family of operating systems. It is developed and sold by Microsoft.  Microsoft has released numerous versions of the Windows operating system. Some of the notable ones include Windows 3.1, Windows 95, Windows 98, Windows XP, Windows Vista, Windows 7, Windows 8, and Windows 10. Each version brought improvements, new features, and changes to the user interface. Microsoft has released numerous versions of the Windows operating system. Some of the notable ones include Windows 3.1, Windows 95, Windows 98, Windows XP, Windows Vista, Windows 7, Windows 8, and Windows 10. Each version brought improvements, new features, and changes to the user interface. Windows 10  As of my last update, Windows 10 is the latest major release. It was first released in July 2015 and has undergone several updates since then. Windows 10 is designed to be a unified operating system across various device types, including desktops, laptops, tablets, and hybrid devices. Here are some key points about Windows.

1. User Interface: Windows operating systems typically have a graphical user interface (GUI) that includes a desktop and a Start menu. 
2. Compatibility: Windows has a vast ecosystem of software applications and hardware drivers, making it compatible with a wide range of third-party software and hardware.
3. Windows Update: Microsoft regularly releases updates for Windows to provide security patches, bug fixes, and feature enhancements. 
4. Security Features: Windows includes various security features, such as Windows Defender (an antivirus program), BitLocker (for disk encryption), Windows Firewall, and user account control (UAC).
5. Microsoft Store: Windows 10 includes the Microsoft Store, where users can download and install apps, 
6. Cortana: Windows 10 integrates Cortana, a virtual assistant that provides voice-activated commands and personalized recommendations.

Linux OS

Linux is an open-source, Unix-like operating system kernel that serves as the foundation for a wide range of operating systems known as Linux distributions or "distros." Developed by Linus Torvalds in 1991, Linux has become a popular choice for servers, embedded systems, and personal computing. Linux's flexibility, stability, and open-source nature have contributed to its widespread adoption in diverse computing environments. It has become a cornerstone of the open-source software movement and a critical player in the world of computing. Here are some key points about Linux.

1. Open Source: Linux is distributed under the terms of the GNU General Public License (GPL), making its source code freely available to the public. 
2. Linux Distributions: A Linux distribution is a complete operating system built around the Linux kernel. Examples include Ubuntu, Fedora, Debian, CentOS, Arch Linux, and many others. 
3. Package Management: Most Linux distributions use package management systems to simplify software installation, updates, and removal. Package managers, such as APT (Advanced Package Tool) on Debian-based systems or YUM (Yellowdog Updater Modified) on Red Hat-based systems, automate the process of managing software packages.
4. Shell and Command-Line Interface (CLI): Linux systems provide a powerful command-line interface (CLI) where users can interact with the system using a shell. 
5. Graphical User Interface (GUI): While Linux is often used with a command-line interface, many desktop environments provide a graphical user interface. 
6. Multiuser and Multitasking: Linux, like its Unix predecessors, is a multiuser and multitasking operating system. 
7. Security and Permissions: Linux has a robust security model. It employs file permissions, user accounts, and groups to control access to system resources. 
8. Server and Embedded Systems: Linux is widely used as a server operating system, powering a significant portion of web servers, cloud infrastructure, and network devices.
9. Community and Development: The Linux community is vast and active. Contributors, ranging from individual developers to large corporations, continually enhance and maintain the Linux kernel and associated software.
10. Variety of Architectures: Linux is designed to run on various hardware architectures, 
11. Live and Installable: Many Linux distributions offer a "live" mode, allowing users to run the operating system from a USB or DVD without installing it on the hard drive. 

Key differences between Windows and Linux:

1. Source Code and Licensing: Windows: Windows is a proprietary operating system developed by Microsoft. Its source code is not publicly available, and users need to purchase licenses for its use. Linux: Linux is open-source, meaning its source code is freely available to the public. Users can view, modify, and distribute their own versions under open-source licenses like the GNU General Public License.
2. User Interface: Windows: Windows typically uses the Windows Desktop environment with a graphical user interface (GUI) that includes the Start menu, Taskbar, and various windows and icons. Linux: Linux provides a range of desktop environments (such as GNOME, KDE, Xfce) with different interfaces. Some Linux systems are configured for a graphical desktop, while others may run in a text-based (command-line) interface.
3. File System: Windows: Windows commonly uses file systems like NTFS (New Technology File System) or FAT32 (File Allocation Table). Each disk volume is typically represented by a drive letter (e.g., C: or D:). Linux: Linux supports various file systems, including ext4, XFS, and Btrfs. It follows a hierarchical file system structure with the root directory represented by "/".
4. Command-Line Interface (CLI): Windows: While Windows has a command prompt, it historically relied more on graphical interfaces. With the introduction of PowerShell, Windows has a powerful CLI for scripting and automation. Linux: Linux is known for its robust command-line interface, and many tasks can be efficiently performed using the terminal. The CLI is integral to Linux administration and development.
5. Software Installation: Windows: Software installation on Windows is often done through executable (.exe) installers or MSI packages. There's also the Microsoft Store for UWP (Universal Windows Platform) apps. Linux: Linux uses package management systems, such as APT (Debian/Ubuntu) or YUM (Red Hat/Fedora), for installing, updating, and removing software. Software can also be compiled from source code.
6. Security Model: Windows: Windows has a user account control (UAC) system and uses access control lists (ACLs) for managing permissions. Antivirus software is commonly used for security. Linux: Linux uses a robust permission system with file permissions, users, and groups. It benefits from a security model that separates user and administrative privileges. The need for antivirus software is much lower in Linux environments.
7. System Updates: Windows: Windows Update is the primary mechanism for updating the operating system and other Microsoft software. Linux: Linux distributions often have centralized package managers for updating the entire system, including the kernel and installed software.
8. System Administration: Windows: System administration on Windows is often done through graphical tools and the Control Panel. PowerShell is used for scripting and automation. Linux: System administration on Linux often involves the use of the terminal and configuration files. Tools like SSH and Bash scripting are common for remote administration.
9. Usage Scenarios: Windows: Commonly used on desktops, laptops, and servers. Windows Server editions are widely used for enterprise solutions. Linux: Widely used in server environments, embedded systems, networking devices, and increasingly on desktops and laptops.

 

LOGIC GATE

 

Logic Gates

Logic gates are fundamental building blocks in digital circuits and are used to perform logical operations on binary signals (0s and 1s). They are the basic building blocks of digital circuits and play a crucial role in the design and implementation of digital systems. There are several types of logic gates, each performing a specific logical operation. Here are some common types of logic gates:

AND Gate: The AND gate is one of the fundamental logic gates in digital electronics. It performs the logical AND operation on two binary inputs. The AND gate has two inputs, typically labelled as A and B, and one output. The output is true (1) only when both inputs are true (1). Here's the symbol for an AND gate and its truth table.

Symbol: 

The truth table of a two-input AND basic gate is given as

A	B	Y
0	0	0
0	1	0
1	0	0
1	1	1

OR Gate: The OR gate is another fundamental logic gate in digital electronics. It performs the logical OR operation on two binary inputs. The OR gate has two inputs, typically labelled as A and B, and one output. The output is true (1) if at least one of the inputs is true (1). Here's the symbol for an OR gate and its truth table.

Symbol:

A	B	Y
0	0	0
0	1	1
1	0	1
1	1	1

Output is true (1) when at least one input is true (1).

NOT Gate: The NOT gate, also known as an inverter, is a basic logic gate that performs the logical NOT operation. It takes a single binary input and produces the opposite value as output. If the input is 0, the output is 1, and if the input is 1, the output is 0. Here's the symbol for a NOT gate and its truth table:

Symbol: 

The truth table of NOT gate is as follows

A	Y
0	1
1	0

Output is the opposite of the input.

NAND Gate: The NAND gate, short for NOT-AND gate, is a fundamental logic gate in digital electronics. It performs the opposite of the AND operation. The output of a NAND gate is true (1) unless both of its inputs are true (1). In other words, it produces the complement of the logical AND operation. Here's the symbol for a NAND gate and its truth table

Symbol: 

The truth table of a NAND gate is given as

A	B	Y
0	0	1
0	1	1
1	0	1
1	1	0

Output is false (0) only when both inputs are true (1).

NOR Gate: The NOR gate, short for NOT-OR gate, is another fundamental logic gate in digital electronics. It performs the opposite of the OR operation. The output of a NOR gate is true (1) only if both of its inputs are false (0). In other words, it produces the complement of the logical OR operation. Here's the symbol for a NOR gate and its truth table

Symbol: 

The truth table of a NOR gate is as follows

A	B	Y
0	0	1
0	1	0
1	0	0
1	1	0

Output is false (0) when at least one input is true (1).

XOR Gate (Exclusive OR):The XOR gate, short for Exclusive OR gate, is a fundamental logic gate that produces a true (1) output only when the number of true inputs is odd. If the inputs are all false (0) or all true, the output is false (0). The XOR gate is often used in digital electronics for various purposes, including binary addition and error detection. Here's the symbol for an XOR gate and its truth table

Symbol: 

The truth table of an XOR gate is

A	B	Y
0	0	0
0	1	1
1	0	1
1	1	0

Output is true (1) when the inputs are different.

These logic gates can be combined in various ways to create more complex digital circuits and perform a wide range of logical operations. Digital circuits, including processors and memory units in computers, are built using combinations of these basic logic gates.

Hardware

                      Hardware Hardware 

Any electronic mechanical or electromagnetic device that make up a computer is known as hardware. All the physical component of computer system is called hardware. For example CPU disk drive keyboard etc.

Computer hardware is divided into three parts.  

1. Input Unit
2. Central Processing Unit
3. Output Unit

1-Input Unit:- Input unit is used to to take input (data, information and instruction)from user. Some of the major input devices are as follows.

1-Keyboard

2-Mouse

3-Joy stick

4-Light Pen

5-Scanner etc. 

1-Keyboard:- Keyboard is the most important input unit of the computer. It is used to input data and instructions into the computer. The keyboard can have 101 or more keys. The keyboard keys can be divided into three parts.

I-Alphabetic key:- The total number of alphabets is 26 (A to Z). These keys are located in the middle                                   of the keyboard. These are used to input the alphabet.

II-Numeric Key:- The total number of numeric is 10 (from 0 to 9). These are located in two places on                                the keyboard. Used to input the numbers.

III-Special character key:- These keys are used to input special symbols (#,@,+,(,),",*,:,,; etc.).

IV-Arrow key:-The total number of arrows is 4. It is used to move the arrow in four different                                           directions. These are located in two places on the keyboard.

V-Special Key:- These keys are used to perform special tasks. Some of the major special keys are as                                 follows. Enter, Caps lock, Backspace, Tab, Delete, Escape, Alt, Ctrl, Insert etc. 

VI-Function key:- The use of the function key is different in different software. Tomorrow number is 12 (F1 to F12). It is located on the first row of the keyboard. 

 2-Mouse:- Mouse was invented in 1977 by Stanford Laboratory scientist "Douglas Engelbart".. It is used in graphical user interface based operating systems. I have two or three buttons. It is used to control the head. With its help, actions like click, double click, right click, dragon drop etc. are done. It is also called pointing device. There are three types of mouse.

1-Mechanical Mouse
2-optical mouse
3-cordless mouse

 3-Joystick:- This is also an input device. It has a handle that can be rotated 360 degrees. It also has buttons by which to operate the joystick. It is used to play games.

4-Trackball:- In this the hair is fixed on the upper surface. It is rotated with the thumb and the fingers are on the button, it is used mostly in laptops.

 5-Light pen:- It is a pointing device which is used like a mouse to control the pointer on the screen. There is a pad in it and there is a pen, when the pen is run on the pad, the pointer rotates. It is used to create pictures, figures and signatures on the computer.

6-Scanner:- Scanner is used to store any document or picture available on the paper in digital form in the computer's memory. The scanner stores the document electronically in the computer's memory.

7-Optical Mark Reader:- Optical Mark Reader is also called OMR. It is used to check the presence or absence of a pencil or pen mark on the paper. It is mainly used in the evaluation of answer sheets.

8-Bar Code Reader:- Bar code reader is used to read the code printed on the packet of a commercial product. It provides information related to the product. It is used in shopping malls and shops in big cities.

9-Magnetic Ink Character Reader:- Magnetic Ink Character Reader is also called M.I0C.R0 in short. It is used to read any special type of ink on checks and drafts. It is mainly used in banks.

10-Webcam:- Web camera is mainly used for taking pictures or making videos. Nowadays it is mainly used in video chatting.

 2-Central Processing Unit:- The Central Processing Unit is the most important unit of the computer. Through this all the parts of the computer are operated and controlled. The efficiency, working speed and efficiency of a computer system all depend on the CPU itself.

The main reasons for CPU are as follows.
1- To operate and control all the parts of the computer.
2- Processing the data.
3- To control the movement of data between different parts of the computer.
Computer CPU can be divided into three parts.
1-Arithmetical Logical Unit
2-Control Unit
3-Register

1-Arithmetical Logical Unit:- The function of Arithmetical Logical Unit is to perform all kinds of mathematical calculations and logical operations in the computer system. It performs all kinds of mathematical operations and logical operations. The data stored by the primary memory is sent to the ALU and after the operation, it is sent back to the memory.

2-Control Unit:- All the activities being done by the computer system and its hardware are operated and controlled by this part. The control unit also performs the task of reading and executing the instructions stored in the storage unit, receiving and operating the data from the input unit and passing the result after processing to the output unit.

23-Register:- Registers are small circuits of high speed. Register is used to temporarily store the results obtained after numerical and logical operations.

Memory :- The part of the computer that is used to store data and files. The lowest unit of storing data in a computer is called a bit. The main units of measurement of memory are as follows.

1 Bit = Binary Digit (0 or 1)
8 Bits=1 Byte
1024 bytes = 1 Kilo Byte
1024 Kilobytes = 1 Mega Byte
1024 Mega Bytes = 1 Giga Byte
1024 Gigabytes = 1 Terra Byte
1024 Terra Bytes = 1 Pete Bites

Computer memory can be divided into two parts.
1-primary memory
2-secondary memory

1-Primary Memory:- Primary memory is also called main memory or internal memory. The data and programs being executed by the CPU are stored in this memory. Primary memory has less storage capacity but higher speed. Primary memory can be divided into the following two parts.
1-RAM
2-ROM
1-RAM: - This is a temporary memory and when the computer is turned off, the information stored in it is destroyed. After the execution of the program by the CPU, the new data is loaded into RAM by deleting the data stored in RAM. There are two types of RAM:

A-Dynamic RAM

B-Static RAM

A-Dynamic RAM:- The information written in Dynamic RAM has to be rewritten after a few milliseconds otherwise it gets expired. The speed of this RAM is high but the storage capacity is less.

B- Static RAM: - There is no need to write the information stored in it again and again. The information is stored as long as the electric current continues to flow. The storage capacity of this RAM is low but the speed is high. This RAM is more expensive than static.

Read Only Memory:- It is happening in such a way in which the written information can be read only, in which neither new information can be written nor the written information can be changed. Or there is permanent memory, the information written in it does not end even after the computer is turned off. The information stored in the ROM is called BIAS (Basic Input Output System BIOS).
There are three types of ROM.
A-PROM(PROGRAMMABLE READ ONLY MEMORY)

B-EPROM(erasable programmable read only memory)

C-EEPROM(electrically erasable programmable read only memory)  

 A-PROM(PROGRAMMABLE READ ONLY MEMORY):- Music program once in PROM can neither be changed nor removed.

B-EPROM (erasable programmable read only memory):- Program stored in EPROM can be erased with the help of ultraviolet rays and can store new programs in it by reuse.

C-EEPROM (electrically erasable programmable read only memory):- Programs stored in EEPROM can also be changed, in this RAM, electrical method is used to erase the music program.

2-Secondary memory:- Secondary memory is also called auxiliary memory or external memory. Secondary memory is cheaper than primary memory and has more storage capacity. Secondary memory is used to store information temporarily. Some of the major secondary memory devices are as follows.

A-magnetic tape
B-floppy disk
C-Hard Disk
D-compact disc
E-Pan Drive
F-memory card

A-Magnetic tape:- Magnetic tape is a device of a rectangular structure. In this, hundreds feet long green coloured magnetic tape is used. This tape is coated with ferrous oxide. Both read/write operations can be done on it. A magnetic tape drive is used to read data from it. Its use is in very limited quantity.

2-Floppy Disk:- Floppy disk is a square thin and light in weight storage issue. Its data storage capacity can range from 100 KB to 2 MB. A floppy disk drive is required to read/write data on it. Presently it is being used sparingly.

From the point of view of size, there are two types of floppy :-
Floppy Disk

1- 5½ Diameter

2- Floppy Disk with a diameter of 23½

Floppy Disk 1- 5½ diameter: - It was invented in the year 1976 and it is also protected by plastic jacket. Its storage capacity varies from 360 KB to 2.44 MB.

Floppy Disk 2- 3½ diameter: - It was first used in Apple computer. Which is smaller than the previous floppy. Its storage capacity varies from 310 KB to 2.88 MB.

3-Hard Disk:- Hard disk is the most important unit used in computer storage. It is also called a fixed disk because it is permanently mounted inside the CPU. In a hard disk, several circular plates are connected at the same distance, data is stored on both surfaces of these plates. For each power there is a separate read write head that performs the task of writing and reading the data on that surface. The storage capacity of hard disk ranges from GB to TB.

4-Optical Disk: - is a flat, circular polycarbonate disc, on which data is stored in the form of pits inside a flat surface, in which data is stored by optical. There are two types of optical disc. of happens. 1-CD 2-DVD

1-CD:- First of all, let's talk about CD, we also call CD by the name of compact disc, it is such an optical medium that saves our digital data. There was a time when we used to use reeled cassettes, the invention of CD completely killed the cassettes in the market. About 700 MB of data can be saved in a standard CD. The data in a CD is saved in the form of a dot, in fact the laser sensor installed in the CD drive reads the reflected light from the CD's dot and creates an image in our device.

2-DVD:- DVD means Digital Versatile Disc, DVD was started after CD, although both CD and DVD look the same, but there is a difference in their data capacity, more data can be saved in DVD than CD. could. Meaning the user can save data from about 4.7 GB to 17 GB in DVD. After the advent of DVD, there was a huge decrease in the demand for CDs in the market.

5-Pen Drive: - It is known as Flash Drive, nowadays most Flash Drive is used to store data, it is an external device which is used separately in the computer. | It is also very small and light in size, Store data can also be read in it and it can also be improved. Flash Drive has a small Pried Circuit Board which is covered with a plastic or metal cover so it is strong. This is a Plug-and-Play tool. Today it is normally available in capacities like 2 GB, 4 GB, 8 GB, 16 GB, 32 GB, 64 GB, 128 GB etc.

6-Memory Card:- Memory card is used to store data in camera, mobile, and computer. Its storage capacity can range from 1GB to 32GB.

Output Unit:-The output unit is used to display data and results.
Output units are used to display data and results. Some of the major output devices are as follows.
1-monitor
2-Printer
3-plotter
4-speaker

1-Monitor:- Monitor is a major output device. It is also called computer screen or visual display unit. The data displayed on it can be seen. Display is the process of showing the output on the screen or monitor. Any shape on a monitor is made up of tiny dots called pixels. These pixels are arranged in the form of rows and columns in the monitor. It is also called visual display unit. It looks like a TV. Monitor is one of the most important output device.

Without it the computer is incomplete. It displays the output as a soft copy on its screen.
Monitor classification by colour
 1-monochrome monitor
2-Grey-Scale monitor
3-Color Monitor

1-Monochrome: - This word is made up of two words mono meaning single and chrome meaning colour, so it is called Single Colour Display and it shows the monitor output as Black & - Displays as.

2-Gray-Scale:- These monitors are similar to monochrome but it displays any type of display (Gary Shades), this type of monitor is mostly handy computer like laptop. ) are used.

3-Color Monitors:- Such a monitor displays the output in the form of adjustment of RGB (Red-Green-Blue) radiations due to the principle such monitors are able to display graphics in high resolution. are capable. According to the capacity of the computer memory, such monitors have the ability to display output in colours ranging from 16 to 16 lakhs.

Classification of monitors by technology

1-CRT Monitor

2-LCD (Liquid Crystal Display)

3-LED ( Light Emitting Diode)

1-CRT Monitor:- The most commonly used Output Device is also called VDU (Visual Display Unit), its main part is cathode Ray Tube which is generally called Picture Tube. Most of the monitors have picture tube element which is used for TV. This tube is similar to the set CRT This technology is called cheap and provides output in perfect colour. CRT has electron gun which emits a beam of electrons and cathode rays. This electron beam is passed from electronic grid to reduce the speed of electrons on CRT monitor. Phosphorus is coding, so as soon as the electronic beam hits the screen, the pixels start shining and the image appears on the screen.

2-LCD (Liquid Crystal Display): - Liquid Crystal Display is also known as LCD, it is a digital technology that creates a shape through a liquid crystal on a flat surface, it takes less space, it takes less energy and than traditional Cathode ray tube produces relatively less heat than the monitor, this display was first used in laptops, but now this screen is also being used for desktop computers.

2-Printer:- Printer is used to print data and information on paper. The information displayed on the printer is called hard copy. On the basis of technology there are two types of printers.

1-Impact Printer

2-Non Impact Printer

1-Impact Printer:- Impact printers are those printers in which there is contact between the print head and the paper. To print each character, the print head hits the paper. It uses a metal hammer as the print head that strikes the ribbon on the paper. Due to this collision the shape of the printhead is printed on the paper. The following printers come under the category of impact printers.

1. DOT MATRIX PRINTER
2. DAISY WHEEL PRINTER
3. LINE PRINTER
4. CHAIN ​​PRINTER
5. DRUM PRINTER

2-Non-Impact Printer(Non-Impact Printer):- Those printers in which there is no contact between printhead and paper are called non-impact printers. Non-impact printers will have high level of printing quality. The following printers come under the category of non-impact printers.

1. LASER PRINTER
2. INKJET PRINTER
3. MULTI FUNCTION PRINTER
4. THERMAL PRINTER

                Major Printers

1-Dot Matrix Printer (Dot Matrix Printer):- This printer is an impact printer. The printer head of this printer has a sole of many three, which when each pin touches the ribbon and the paper prints a stop. group occurs. The pin printheads of one column at a time come out and print a scold so that a character is formed in several steps and the print progresses in the direction of the line. The speed of dot matrix printers can range from 30 to 600 characters per second. The printing quality of this printer is not good.

2-Daisy Wheel Printer(Daisy Wheel Printer):- It is an impact printer with solid currency letter. The shape of its print-head is similar to that of a daisy flower, hence it is called Daisy Wheel Printer. This printer prints high quality printouts but its speed is slow. The printhead consists of a circle whose spokes of a solid spoke of a character while rotate the print position and strike the paper with a hammer on top of the ribbon to print a character.

3-Line Printer:- Line printer is also an impact printer. It is used in large size computers. Its speed is very high. It can print 300 to 3000 lines in a minute. These tenders are used in mini and mainframe computers. The following three printers come under the category of line printers.

1. drum printer
2. chain printer
3. band printer

4-Laser Printer (Laser Printer):- Laser Printer is a non-impact printer. Dry ink is used to print in this printer. This printer also uses dots to print. These dots are very small and close enough to provide very clear print quality. 300 to 600 D.P.I. Up to or more reservations can be printed. The quality of the inventor is very good. Both colour and black and white prints can be taken using them.

5- Inkjet printer (inkjet printer):- Inkjet printer is also a non-impact printer. In this, characters and graphics are printed by spraying drops of ink on the paper by a nozzle. The output of this printer is very clear because the letter formation in it consists of many teeth. The print quality of this printer is usually 300 dot per inch.

3-Plotter:- Plotter is also a major output unit. It is used to print pictures. Plaster is used for making maps, graphs and printing. There are two types of plotters.

1. Drum Pen Plotter
2. Flatbed Plotter

A-Drum pen plotter:- This is a plotter in which a pen is used to make a shape. With the help of a pen, drawings are made on the paper, in this device the paper is mounted on a drum which is slowly moved and prints 10.

B-Flatbed Plotter (Flat Plotter):- In this, the paper is placed in a stationary state on the Edward or tray. In this, a pan is kept on one arm, which makes a picture by moving up and down on the paper from the motor left and right, in which the pen is controlled from the computer.