Computer Fundamentals 简明教程

Computer Fundamentals - Quick Guide

Computer - Overview

当今世界是一个信息丰富的世界，每个人都有必要了解计算机。计算机是电子数据处理设备，它接受并存储数据输入，处理数据输入并以所需格式生成输出。

Today’s world is an information-rich world and it has become a necessity for everyone to know about computers. A computer is an electronic data processing device, which accepts and stores data input, processes the data input, and generates the output in a required format.

本教程的目的是向你介绍计算机及其基础知识。

The purpose of this tutorial is to introduce you to Computers and its fundamentals.

Functionalities of a Computer

如果从非常广泛的意义上来看，任何数字计算机都执行以下五个功能 −

If we look at it in a very broad sense, any digital computer carries out the following five functions −

Step 1 − 以数据形式接收输入。

Step 1 − Takes data as input.

Step 2 − 将数据/指令存储在内存中，并根据需要使用它们。

Step 2 − Stores the data/instructions in its memory and uses them as required.

Step 3 − 处理数据并将它们转换成有用的信息。

Step 3 − Processes the data and converts it into useful information.

Step 4 − 生成输出。

Step 4 − Generates the output.

Step 5 − 控制以上四个步骤。

Step 5 − Controls all the above four steps.

Advantages of Computers

以下是计算机的某些优点。

Following are certain advantages of computers.

High Speed

Computer is a very fast device.
It is capable of performing calculation of very large amount of data.
The computer has units of speed in microsecond, nanosecond, and even the picosecond.
It can perform millions of calculations in a few seconds as compared to man who will spend many months to perform the same task.

Accuracy

In addition to being very fast, computers are very accurate.
The calculations are 100% error free.
Computers perform all jobs with 100% accuracy provided that the input is correct.

Storage Capability

Memory is a very important characteristic of computers.
A computer has much more storage capacity than human beings.
It can store large amount of data.
It can store any type of data such as images, videos, text, audio, etc.

Diligence

Unlike human beings, a computer is free from monotony, tiredness, and lack of concentration.
It can work continuously without any error and boredom.
It can perform repeated tasks with the same speed and accuracy.

Versatility

A computer is a very versatile machine.
A computer is very flexible in performing the jobs to be done.
This machine can be used to solve the problems related to various fields.
At one instance, it may be solving a complex scientific problem and the very next moment it may be playing a card game.

Reliability

A computer is a reliable machine.
Modern electronic components have long lives.
Computers are designed to make maintenance easy.

Automation

Computer is an automatic machine.
Automation is the ability to perform a given task automatically. Once the computer receives a program i.e., the program is stored in the computer memory, then the program and instruction can control the program execution without human interaction.

Reduction in Paper Work and Cost

The use of computers for data processing in an organization leads to reduction in paper work and results in speeding up the process.
As data in electronic files can be retrieved as and when required, the problem of maintenance of large number of paper files gets reduced.
Though the initial investment for installing a computer is high, it substantially reduces the cost of each of its transaction.

Disadvantages of Computers

以下是计算机的某些缺点。

Following are certain disadvantages of computers.

No I.Q.

A computer is a machine that has no intelligence to perform any task.
Each instruction has to be given to the computer.
A computer cannot take any decision on its own.

Dependency

It functions as per the user’s instruction, thus it is fully dependent on humans.

Environment

The operating environment of the computer should be dust free and suitable.

No Feeling

Computers have no feelings or emotions.
It cannot make judgment based on feeling, taste, experience, and knowledge unlike humans.

Computer - Applications

在本章中，我们将讨论计算机在各个领域的应用。

In this chapter, we will discuss the application of computers in various fields.

Business

计算机具有很高的计算速度、勤奋、准确性、可靠性或通用性，这使其成为所有商业组织中不可或缺的一部分。

A computer has high speed of calculation, diligence, accuracy, reliability, or versatility which has made it an integrated part in all business organizations.

计算机用于商业组织的 −

Computer is used in business organizations for −

Payroll calculations
Budgeting
Sales analysis
Financial forecasting
Managing employee database
Maintenance of stocks, etc.

Banking

如今，银行业务几乎完全依赖计算机。

Today, banking is almost totally dependent on computers.

银行提供以下便利 −

Banks provide the following facilities −

Online accounting facility, which includes checking current balance, making deposits and overdrafts, checking interest charges, shares, and trustee records.
ATM machines which are completely automated are making it even easier for customers to deal with banks.

Insurance

保险公司借助计算机来更新所有记录。保险公司、金融机构和股票经纪公司广泛使用计算机来解决他们的问题。

Insurance companies are keeping all records up-to-date with the help of computers. Insurance companies, finance houses, and stock broking firms are widely using computers for their concerns.

保险公司会维护所有客户的数据库，其中包含显示以下信息的数据 −

Insurance companies are maintaining a database of all clients with information showing −

Procedure to continue with policies
Starting date of the policies
Next due installment of a policy
Maturity date
Interests due
Survival benefits
Bonus

Education

计算机在提供教育系统的大量设施方面有所帮助。

The computer helps in providing a lot of facilities in the education system.

The computer provides a tool in the education system known as CBE (Computer Based Education).
CBE involves control, delivery, and evaluation of learning.
Computer education is rapidly increasing the graph of number of computer students.
There are a number of methods in which educational institutions can use a computer to educate the students.
It is used to prepare a database about performance of a student and analysis is carried out on this basis.

Marketing

在市场营销中，计算机的用途如下：

In marketing, uses of the computer are following −

Advertising − With computers, advertising professionals create art and graphics, write and revise copy, and print and disseminate ads with the goal of selling more products.
Home Shopping − Home shopping has been made possible through the use of computerized catalogues that provide access to product information and permit direct entry of orders to be filled by the customers.

Healthcare

计算机已成为医院、实验室和药房的重要组成部分。它们被用于医院以保存患者和药品的记录。它还用于扫描和诊断各种疾病。心电图、脑电图、超声波和 CT 扫描等也由计算机化的机器完成。

Computers have become an important part in hospitals, labs, and dispensaries. They are being used in hospitals to keep the record of patients and medicines. It is also used in scanning and diagnosing different diseases. ECG, EEG, ultrasounds and CT scans, etc. are also done by computerized machines.

以下是计算机被用于的一些主要的医疗保健领域。

Following are some major fields of health care in which computers are used.

Diagnostic System − Computers are used to collect data and identify the cause of illness.
Lab-diagnostic System − All tests can be done and the reports are prepared by computer.
Patient Monitoring System − These are used to check the patient’s signs for abnormality such as in Cardiac Arrest, ECG, etc.
Pharma Information System − Computer is used to check drug labels, expiry dates, harmful side effects, etc.
Surgery − Nowadays, computers are also used in performing surgery.

Engineering Design

计算机广泛用于工程目的。

Computers are widely used for Engineering purpose.

其中一个主要领域是 CAD（计算机辅助设计），它可以创建和修改图像。其中一些领域包括：

One of the major areas is CAD (Computer Aided Design) that provides creation and modification of images. Some of the fields are −

Structural Engineering − Requires stress and strain analysis for design of ships, buildings, budgets, airplanes, etc.
Industrial Engineering − Computers deal with design, implementation, and improvement of integrated systems of people, materials, and equipment.
Architectural Engineering − Computers help in planning towns, designing buildings, determining a range of buildings on a site using both 2D and 3D drawings.

Military

计算机在国防中被广泛使用。现代坦克、导弹、武器等。军队也使用计算机化控制系统。计算机已使用的一些军事领域如下所述：

Computers are largely used in defence. Modern tanks, missiles, weapons, etc. Military also employs computerized control systems. Some military areas where a computer has been used are −

Missile Control
Military Communication
Military Operation and Planning
Smart Weapons

Communication

通信是一种传达信息、思想、图片或言语的方式，接收者可以清晰、正确地接收和理解信息。此类别中的一些主要领域是：

Communication is a way to convey a message, an idea, a picture, or speech that is received and understood clearly and correctly by the person for whom it is meant. Some main areas in this category are −

E-mail
Chatting
Usenet
FTP
Telnet
Video-conferencing

Government

计算机在政府服务中发挥着重要作用。此类别中的一些主要领域是：

Computers play an important role in government services. Some major fields in this category are −

Budgets
Sales tax department
Income tax department
Computation of male/female ratio
Computerization of voters lists
Computerization of PAN card
Weather forecasting

Computer - Generations

在计算机术语中，代指计算机技术的变更/曾使用的技术。最初，代指这一术语用来区分不同的硬件技术。如今，代指包括硬件和软件，它们共同构成了整个计算机系统。

Generation in computer terminology is a change in technology a computer is/was being used. Initially, the generation term was used to distinguish between varying hardware technologies. Nowadays, generation includes both hardware and software, which together make up an entire computer system.

迄今为止，已知的计算机代共有五个。每代计算机及其时间段和特性均已详细讨论过。在下表中，已经提到了每代计算机的近似日期，均为通常认可的日期。

There are five computer generations known till date. Each generation has been discussed in detail along with their time period and characteristics. In the following table, approximate dates against each generation has been mentioned, which are normally accepted.

以下是计算机的五个主要代。

Following are the main five generations of computers.

S.No	Generation & Description
1	First GenerationThe period of first generation: 1946-1959. Vacuum tube based.
2	Second GenerationThe period of second generation: 1959-1965. Transistor based.
3	Third GenerationThe period of third generation: 1965-1971. Integrated Circuit based.
4	Fourth GenerationThe period of fourth generation: 1971-1980. VLSI microprocessor based.
5	Fifth GenerationThe period of fifth generation: 1980-onwards. ULSI microprocessor based.

Computer - Types

计算机可以大致按其速度和计算能力进行分类。

Computers can be broadly classified by their speed and computing power.

S.No.

Type

Specifications

PC (Personal Computer)

It is a single user computer system having moderately powerful microprocessor

Workstation

It is also a single user computer system, similar to personal computer however has a more powerful microprocessor.

Mini Computer

It is a multi-user computer system, capable of supporting hundreds of users simultaneously.

Main Frame

It is a multi-user computer system, capable of supporting hundreds of users simultaneously. Software technology is different from minicomputer.

Supercomputer

It is an extremely fast computer, which can execute hundreds of millions of instructions per second.

PC (Personal Computer)

可以将个人电脑定义为一种为个人用户设计的体积小、价格相对低廉的计算机。个人电脑基于微处理器技术，使制造商能够将整个 CPU 放置在一个芯片上。企业将个人电脑用于文字处理、会计、桌面出版以及运行电子表格和数据库管理应用程序。在家中，个人电脑最流行的用途是玩游戏和浏览互联网。

A PC can be defined as a small, relatively inexpensive computer designed for an individual user. PCs are based on the microprocessor technology that enables manufacturers to put an entire CPU on one chip. Businesses use personal computers for word processing, accounting, desktop publishing, and for running spreadsheet and database management applications. At home, the most popular use for personal computers is playing games and surfing the Internet.

虽然个人电脑设计为单用户系统，但这些系统通常被连接在一起形成一个网络。在性能方面，当今的 Macintosh 和个人电脑高端型号提供的计算能力和图形功能与 Sun Microsystems、惠普、戴尔的低端工作站相当。

Although personal computers are designed as single-user systems, these systems are normally linked together to form a network. In terms of power, now-a-days high-end models of the Macintosh and PC offer the same computing power and graphics capability as low-end workstations by Sun Microsystems, Hewlett-Packard, and Dell.

Workstation

工作站是一种用于工程应用程序（CAD/CAM）、桌面出版、软件开发以及其他需要适量计算能力和相对较高的图形处理能力的此类应用程序的计算机。

Workstation is a computer used for engineering applications (CAD/CAM), desktop publishing, software development, and other such types of applications which require a moderate amount of computing power and relatively high quality graphics capabilities.

工作站通常配备大屏幕高分辨率图形显示器、大量 RAM、内置网络支持以及图形用户界面。大多数工作站还配备大容量存储设备，如磁盘驱动器，但一种称为无盘工作站的特殊类型工作站不配备磁盘驱动器。

Workstations generally come with a large, high-resolution graphics screen, large amount of RAM, inbuilt network support, and a graphical user interface. Most workstations also have mass storage device such as a disk drive, but a special type of workstation, called diskless workstation, comes without a disk drive.

工作站的常见操作系统是 UNIX 和 Windows NT。与个人电脑类似，工作站也是单用户计算机，但通常连接在一起形成局域网，尽管它们也可作为独立系统使用。

Common operating systems for workstations are UNIX and Windows NT. Like PC, workstations are also single-user computers like PC but are typically linked together to form a local-area network, although they can also be used as stand-alone systems.

Minicomputer

它是一种中型多处理系统，能够同时最多支持 250 个用户。

It is a midsize multi-processing system capable of supporting up to 250 users simultaneously.

Mainframe

大型计算机体积非常大，是一款昂贵的计算机，能够同时支持数百甚至数千个用户。大型计算机同时执行许多程序并支持多个程序同时执行。

Mainframe is very large in size and is an expensive computer capable of supporting hundreds or even thousands of users simultaneously. Mainframe executes many programs concurrently and supports many simultaneous execution of programs.

Supercomputer

超级计算机是目前最快的计算机之一。超级计算机非常昂贵，用于需要大量数学计算（数值处理）的特种应用。

Supercomputers are one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require immense amount of mathematical calculations (number crunching).

例如，天气预报、科学模拟、（动画）图形、流体动力计算、核能研究、电子设计和地质数据分析（例如石化勘探）。

For example, weather forecasting, scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting).

Computer - Components

所有类型的计算机遵循同一种基本逻辑结构，并执行以下五个基本操作来将原始输入数据转换为对用户有用的信息。

All types of computers follow the same basic logical structure and perform the following five basic operations for converting raw input data into information useful to their users.

S.No.

Operation

Description

Take Input

The process of entering data and instructions into the computer system.

Store Data

Saving data and instructions so that they are available for processing as and when required.

Processing Data

Performing arithmetic, and logical operations on data in order to convert them into useful information.

Output Information

The process of producing useful information or results for the user, such as a printed report or visual display.

Control the workflow

Directs the manner and sequence in which all of the above operations are performed.

Input Unit

此单元包含设备，借助这些设备，我们可以将数据输入计算机。此单元在用户和计算机之间创建链接。输入设备将信息翻译成计算机可以理解的形式。

This unit contains devices with the help of which we enter data into the computer. This unit creates a link between the user and the computer. The input devices translate the information into a form understandable by the computer.

CPU (Central Processing Unit)

CPU 被认为是计算机的大脑。CPU 执行所有类型的数据处理操作。它存储数据、中间结果和指令（程序）。它控制计算机所有部分的操作。

CPU is considered as the brain of the computer. CPU performs all types of data processing operations. It stores data, intermediate results, and instructions (program). It controls the operation of all parts of the computer.

CPU 本身具有以下三个组件 -

CPU itself has the following three components −

ALU (Arithmetic Logic Unit)
Memory Unit
Control Unit

Output Unit

输出单元由设备组成，借助这些设备，我们可以从计算机获取信息。该单元在计算机和用户之间形成链接。输出设备将计算机的输出翻译成用户可以理解的形式。

The output unit consists of devices with the help of which we get the information from the computer. This unit is a link between the computer and the users. Output devices translate the computer’s output into a form understandable by the users.

Computer - CPU(Central Processing Unit)

中央处理单元 (CPU) 包含以下功能 -

Central Processing Unit (CPU) consists of the following features −

CPU is considered as the brain of the computer.
CPU performs all types of data processing operations.
It stores data, intermediate results, and instructions (program).
It controls the operation of all parts of the computer.

CPU 本身具有以下三个组件。

CPU itself has following three components.

Memory or Storage Unit
Control Unit
ALU(Arithmetic Logic Unit)

Memory or Storage Unit

该单元可以存储指令、数据和中间结果。该单元在需要时向计算机的其他单元提供信息。它也称为内部存储单元或主内存或主存储器或随机存取存储器 (RAM)。

This unit can store instructions, data, and intermediate results. This unit supplies information to other units of the computer when needed. It is also known as internal storage unit or the main memory or the primary storage or Random Access Memory (RAM).

它的尺寸会影响速度、功率和能力。主存和辅存是计算机中的两种存储器类型。内存单元的功能 -

Its size affects speed, power, and capability. Primary memory and secondary memory are two types of memories in the computer. Functions of the memory unit are −

It stores all the data and the instructions required for processing.
It stores intermediate results of processing.
It stores the final results of processing before these results are released to an output device.
All inputs and outputs are transmitted through the main memory.

Control Unit

该单元控制计算机所有部分的操作，但不会执行任何实际的数据处理操作。

This unit controls the operations of all parts of the computer but does not carry out any actual data processing operations.

该单元的功能 -

Functions of this unit are −

It is responsible for controlling the transfer of data and instructions among other units of a computer.
It manages and coordinates all the units of the computer.
It obtains the instructions from the memory, interprets them, and directs the operation of the computer.
It communicates with Input/Output devices for transfer of data or results from storage.
It does not process or store data.

ALU (Arithmetic Logic Unit)

该单元由两个子部分组成，即：

This unit consists of two subsections namely,

Arithmetic Section
Logic Section

Arithmetic Section

算术部分的功能是执行加法、减法、乘法和除法等算术运算。所有复杂运算都是通过重复使用上述运算来完成的。

Function of arithmetic section is to perform arithmetic operations like addition, subtraction, multiplication, and division. All complex operations are done by making repetitive use of the above operations.

Logic Section

逻辑部分的功能是执行比较、选择、匹配和合并数据之类的逻辑运算。

Function of logic section is to perform logic operations such as comparing, selecting, matching, and merging of data.

Computer - Input Devices

以下是一些计算机中使用的重要输入设备：

Following are some of the important input devices which are used in a computer −

Keyboard
Mouse
Joy Stick
Light pen
Track Ball
Scanner
Graphic Tablet
Microphone
Magnetic Ink Card Reader(MICR)
Optical Character Reader(OCR)
Bar Code Reader
Optical Mark Reader(OMR)

Keyboard

键盘是最常见且非常流行的输入设备，可帮助将数据输入计算机。键盘的布局类似于传统打字机，尽管提供了一些额外的键以执行其他功能。

Keyboard is the most common and very popular input device which helps to input data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing additional functions.

键盘有两种尺寸，84 键或 101/102 键，但现在 Windows 和互联网也可以使用 104 键或 108 键的键盘。

Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.

键盘上的键如下所示：

The keys on the keyboard are as follows −

S.No	Keys & Description
1	Typing Keys These keys include the letter keys (A-Z) and digit keys (09) which generally give the same layout as that of typewriters.
2	Numeric Keypad It is used to enter the numeric data or cursor movement. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machines and calculators.
3	Function Keys The twelve function keys are present on the keyboard which are arranged in a row at the top of the keyboard. Each function key has a unique meaning and is used for some specific purpose.
4	Control keys These keys provide cursor and screen control. It includes four directional arrow keys. Control keys also include Home, End, Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc).
5	Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen.

Mouse

鼠标是最流行的指针设备。它是一款非常有名的光标控制设备，它有一个手掌大小的盒子和一个位于底座的圆球，它感应鼠标的移动，并在按下鼠标按钮时向 CPU 发送相应的信号。

Mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm size box with a round ball at its base, which senses the movement of the mouse and sends corresponding signals to the CPU when the mouse buttons are pressed.

它通常有两个按钮，称为左键和右键，按钮之间有一个滚轮。鼠标可用于控制光标在屏幕上的位置，但不能用于向计算机输入文本。

Generally, it has two buttons called the left and the right button and a wheel is present between the buttons. A mouse can be used to control the position of the cursor on the screen, but it cannot be used to enter text into the computer.

Advantages

Easy to use
Not very expensive
Moves the cursor faster than the arrow keys of the keyboard.

Joystick

操纵杆也是一种定位设备，用于在显示器屏幕上移动光标位置。它是一根棍子，在上下两端都有一个球形球体。下球形球体在插座中移动。操纵杆可以向四个方向移动。

Joystick is also a pointing device, which is used to move the cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. The joystick can be moved in all four directions.

操纵杆的功能类似于鼠标。它主要用于计算机辅助设计 (CAD) 和玩电脑游戏。

The function of the joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.

Light Pen

光笔是一种类似于笔的定位设备。它用于选择显示的菜单项或在显示器屏幕上绘制图片。它由一个光电管和放置在小管中的光学系统组成。

Light pen is a pointing device similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube.

当光笔尖端在显示器屏幕上移动并且按下笔按钮时，其光电传感元件检测屏幕位置并将相应信号发送到 CPU。

When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell sensing element detects the screen location and sends the corresponding signal to the CPU.

Track Ball

轨迹球是一种输入设备，通常用于笔记本电脑，而不是鼠标。这是一个半插入的球体，通过手指在球体上移动，就可以移动指针。

Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse. This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved.

由于未移动整个设备，因此轨迹球所需的占地面积小于鼠标。轨迹球有各种形状，例如球形、按钮形或方形。

Since the whole device is not moved, a track ball requires less space than a mouse. A track ball comes in various shapes like a ball, a button, or a square.

Scanner

扫描仪是一种输入设备，它的工作方式更像复印机。当某些信息存在于纸质上并且需要将其传输到计算机的硬盘上以进行进一步处理时，将使用它。

Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on paper and it is to be transferred to the hard disk of the computer for further manipulation.

扫描仪从源头捕获图像，然后将其转换为可以存储在磁盘上的数字形式。在打印这些图像之前，可以对其进行编辑。

Scanner captures images from the source which are then converted into a digital form that can be stored on the disk. These images can be edited before they are printed.

Digitizer

数字化仪是一种可以将模拟信息转换为数字形式的输入设备。数字化仪可以将来自电视或摄像机的信号转换为一系列可存储在计算机中的数字。它们可以被计算机用来创建任何面向摄像机的图片。

Digitizer is an input device which converts analog information into digital form. Digitizer can convert a signal from the television or camera into a series of numbers that could be stored in a computer. They can be used by the computer to create a picture of whatever the camera had been pointed at.

数字化仪也被称为平板电脑或图形平板电脑，因为它可以将图形和图片数据转换为二进制输入。图形平板电脑作为数字化仪用于精细绘画和图像处理应用程序中。

Digitizer is also known as Tablet or Graphics Tablet as it converts graphics and pictorial data into binary inputs. A graphic tablet as digitizer is used for fine works of drawing and image manipulation applications.

Microphone

麦克风是一种用于输入声音的输入设备，可以将其存储为数字形式。

Microphone is an input device to input sound that is then stored in a digital form.

麦克风用于各种应用程序，例如向多媒体演示文稿中添加声音或混音音乐。

The microphone is used for various applications such as adding sound to a multimedia presentation or for mixing music.

Magnetic Ink Card Reader (MICR)

MICR 输入设备通常用于银行，因为每天要处理大量的支票。银行代码和支票号码印在支票上，用一种特殊的墨水，其中包含机器可读的磁性材料颗粒。

MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank’s code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable.

此读取过程称为磁性墨水字符识别 (MICR)。MICR 的主要优点在于速度快且出错几率低。

This reading process is called Magnetic Ink Character Recognition (MICR). The main advantages of MICR is that it is fast and less error prone.

Optical Character Reader (OCR)

OCR 是一种用于读取印刷文本的输入设备。

OCR is an input device used to read a printed text.

OCR 按字符对文本进行光学扫描，将其转换为机器可读代码，并将文本存储在系统内存中。

OCR scans the text optically, character by character, converts them into a machine readable code, and stores the text on the system memory.

Bar Code Readers

条形码阅读器是一种用于读取条形码数据（光和暗线形式的数据）的设备。条形码数据通常用于商品贴标签、对书进行编号等。它可能是手持式扫描仪，也可能是嵌入式固定扫描仪。

Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a handheld scanner or may be embedded in a stationary scanner.

条形码阅读器扫描条形码图像，将其转换为字母数字值，然后将其送入条形码阅读器连接的计算机。

Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer that the bar code reader is connected to.

Optical Mark Reader (OMR)

OMR 是一种特殊类型的光学扫描仪，用于识别笔或铅笔所做的标记类型。它用于从少数几个选项中进行选择并标记的情况。

OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.

它专门用于检查具有多项选择题的考试答题卷。

It is specially used for checking the answer sheets of examinations having multiple choice questions.

Computer - Output Devices

以下是计算机中使用的一些重要输出设备。

Following are some of the important output devices used in a computer.

Monitors
Graphic Plotter
Printer

Monitors

显示器，通常称为 Visual Display Unit (VDU)，是计算机的主要输出设备。它由称为像素的小点形成图像，这些像素以矩形排列。图像的清晰度取决于像素的数量。

Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.

有两种用于显示器的显示屏类型。

There are two kinds of viewing screen used for monitors.

Cathode-Ray Tube (CRT)
Flat-Panel Display

Cathode-Ray Tube (CRT) Monitor

CRT 显示器由称为像素的小像素组成。像素越小，图像清晰度或分辨率就越好。需要一个以上的点亮像素才能形成一个完整的字符，比如单词“帮助”中的字母“e”。

The CRT display is made up of small picture elements called pixels. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

屏幕上一次只能显示有限数量的字符。屏幕可以划分为一系列字符框 - 可以在其中放置标准字符的屏幕上的固定位置。大多数屏幕可以水平显示 80 个字符的数据，垂直显示 25 行。

A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.

CRT 有一些缺点 −

There are some disadvantages of CRT −

Large in Size
High power consumption

Flat-Panel Display Monitor

相对于 CRT，平板显示器指的是一类视频设备，具有体积更小、重量更轻、功耗更低的特点。可以将它们挂在墙壁上或戴在手腕上。平板显示器的当前用途包括计算器、视频游戏、显示器、笔记本电脑和图形显示器。

The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement in comparison to the CRT. You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include calculators, video games, monitors, laptop computer, and graphics display.

平板显示器分为两种类 −

The flat-panel display is divided into two categories −

Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes).
Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device).

Printers

打印机是一种输出设备，用于在纸张上打印信息。

Printer is an output device, which is used to print information on paper.

有两种类型的打印机 −

There are two types of printers −

Impact Printers
Non-Impact Printers

Impact Printers

击打式打印机通过击打色带上的字符来进行打印，然后将色带压在纸张上。

Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.

击打式打印机的特性如下 −

Characteristics of Impact Printers are the following −

Very low consumable costs
Very noisy
Useful for bulk printing due to low cost
There is physical contact with the paper to produce an image

这类打印机分为两种 −

These printers are of two types −

Character printers
Line printers

Character Printers

字符打印机一次打印一个字符的打印机。

Character printers are the printers which print one character at a time.

它们又分为两种类型：

These are further divided into two types:

Dot Matrix Printer(DMP)
Daisy Wheel

Dot Matrix Printer

在市场上，点阵打印机是最流行的打印机之一。这类打印机很受欢迎，原因在于它们打印简单，价格经济。打印的每个字符都以点阵形式呈现，打印头由大小为 (5*7, 7*9, 9*7 或 9*9) 的针矩阵组成，这些针会伸出来形成字符，这也是它被称为点阵打印机的原因。

In the market, one of the most popular printers is Dot Matrix Printer. These printers are popular because of their ease of printing and economical price. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.

Advantages

Inexpensive
Widely Used
Other language characters can be printed

Disadvantages

Slow Speed
Poor Quality

Daisy Wheel

打印头放置在一个转轮上，与字符对应的针脚就像雏菊（花）的花瓣，这就是为什么它被称为雏菊打印机。这些打印机通常用于办公室的文字处理，这些办公室需要在这里或那里发送一些非常高质量的信件。

Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices that require a few letters to be sent here and there with very nice quality.

Advantages

More reliable than DMP
Better quality
Fonts of character can be easily changed

Disadvantages

Slower than DMP
Noisy
More expensive than DMP

Line Printers

行式打印机一次打印一行。

Line printers are the printers which print one line at a time.

它们分为两种类型−

These are of two types −

Drum Printer
Chain Printer

Drum Printer

这台打印机形状像一个圆筒，因此称为圆筒打印机。圆筒的表面被分成许多轨道。轨道总数等于纸张的尺寸，即对于宽度为 132 个字符的纸张，圆筒将有 132 条轨道。轨道上压印了一个字符集。市场上有 48 个字符集、64 个字符集和 96 个字符集。圆筒转动一圈打印一行。圆筒打印机速度快，每分钟可打印 300 到 2000 行。

This printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute.

Advantages

Very high speed

Disadvantages

Very expensive
Characters fonts cannot be changed

Chain Printer

这台打印机使用一个字符集链条，因此称之为链式打印机。一个标准字符集可以有 48 个、64 个或 96 个字符。

In this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.

Advantages

Character fonts can easily be changed.
Different languages can be used with the same printer.

Disadvantages

Noisy

Non-impact Printers

非冲击打印机在打印字符时不使用色带。这些打印机一次打印一整页，因此它们也被称为页面打印机。

Non-impact printers print the characters without using the ribbon. These printers print a complete page at a time, thus they are also called as Page Printers.

这类打印机分为两种 −

These printers are of two types −

Laser Printers
Inkjet Printers

Characteristics of Non-impact Printers

Faster than impact printers
They are not noisy
High quality
Supports many fonts and different character size

Laser Printers

它们是非冲击页面打印机。它们使用激光灯来产生点，从而形成要打印在页面上的字符。

These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.

Advantages

Very high speed
Very high quality output
Good graphics quality
Supports many fonts and different character size

Disadvantages

Expensive
Cannot be used to produce multiple copies of a document in a single printing

Inkjet Printers

喷墨打印机是基于较新技术的非冲击字符打印机。它们通过将小滴墨水喷洒到纸张上来打印字符。喷墨打印机产生具有可展示特性的高质量输出。

Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features.

它们发出的噪音较小，因为无需敲击，并且有许多可用的打印模式样式。还可以进行彩色打印。某些型号的喷墨打印机还可以生成多份打印副本。

They make less noise because no hammering is done and these have many styles of printing modes available. Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.

Advantages

High quality printing
More reliable

Disadvantages

Expensive as the cost per page is high
Slow as compared to laser printer

Computer - Memory

内存就像人的大脑。它用于存储数据和指令。计算机内存是计算机中的存储空间，其中要处理的数据和处理所需指令被存储。内存被分为称为单元的大量小部分。每个位置或单元都有一个唯一的地址，该地址从零到内存大小减一不等。例如，如果计算机有 64k 个字，那么这个内存单元就有 64 * 1024 = 65536 个内存位置。这些位置的地址从 0 到 65535 不等。

A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells. Each location or cell has a unique address, which varies from zero to memory size minus one. For example, if the computer has 64k words, then this memory unit has 64 * 1024 = 65536 memory locations. The address of these locations varies from 0 to 65535.

内存主要有三种类型 -

Memory is primarily of three types −

Cache Memory
Primary Memory/Main Memory
Secondary Memory

Cache Memory

高速缓存存储器是一种可以加速 CPU 的高速半导体存储器。它充当 CPU 和主存储器之间的缓冲区。它用于保存 CPU 最常使用的数据和程序部分。数据和程序的部分被操作系统从磁盘传输到高速缓存存储器，CPU 可以从那里访问它们。

Cache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory. It is used to hold those parts of data and program which are most frequently used by the CPU. The parts of data and programs are transferred from the disk to cache memory by the operating system, from where the CPU can access them.

Advantages

高速缓存存储器的优点如下 -

The advantages of cache memory are as follows −

Cache memory is faster than main memory.
It consumes less access time as compared to main memory.
It stores the program that can be executed within a short period of time.
It stores data for temporary use.

Disadvantages

高速缓存存储器的缺点如下 -

The disadvantages of cache memory are as follows −

Cache memory has limited capacity.
It is very expensive.

Primary Memory (Main Memory)

主存储器仅保存计算机当前正在使用的那些数据和指令。它有有限的容量，断电时数据会丢失。它通常由半导体器件制成。这些存储器不如寄存器快。需要处理的数据和指令驻留在主存储器中。它分为 RAM 和 ROM 两个子类别。

Primary memory holds only those data and instructions on which the computer is currently working. It has a limited capacity and data is lost when power is switched off. It is generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed resides in the main memory. It is divided into two subcategories RAM and ROM.

Characteristics of Main Memory

These are semiconductor memories.
It is known as the main memory.
Usually volatile memory.
Data is lost in case power is switched off.
It is the working memory of the computer.
Faster than secondary memories.
A computer cannot run without the primary memory.

Secondary Memory

这种类型的内存也称为外部存储器或非易失性存储器。它比主存要慢。它们用于永久存储数据/信息。CPU 不直接访问这些存储器，而通过输入输出例程访问。辅助存储器的内容首先被传输到主存中，然后 CPU 才能访问它。例如，磁盘、CD-ROM、DVD 等。

This type of memory is also known as external memory or non-volatile. It is slower than the main memory. These are used for storing data/information permanently. CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. For example, disk, CD-ROM, DVD, etc.

Characteristics of Secondary Memory

These are magnetic and optical memories.
It is known as the backup memory.
It is a non-volatile memory.
Data is permanently stored even if power is switched off.
It is used for storage of data in a computer.
Computer may run without the secondary memory.
Slower than primary memories.

Random Access Memory

RAM（随机存取存储器）是 CPU 的内部存储器，用于存储数据、程序和程序结果。它是一种读写存储器，在机器工作时存储数据。只要机器关闭，数据就会被抹掉。

RAM (Random Access Memory) is the internal memory of the CPU for storing data, program, and program result. It is a read/write memory which stores data until the machine is working. As soon as the machine is switched off, data is erased.

RAM 中的访问时间与地址无关，这意味着存储器内部的每个存储位置都像其他位置一样容易访问，并且花费相同的时间。RAM 中的数据可以随机访问，但代价很高。

Access time in RAM is independent of the address, that is, each storage location inside the memory is as easy to reach as other locations and takes the same amount of time. Data in the RAM can be accessed randomly but it is very expensive.

RAM 是易失性的，也就是说当我们关闭计算机或断电时，存储在其中的数据就会丢失。因此，计算机通常使用备用不间断电源 (UPS)。RAM很小，无论从物理大小还是它可以容纳的数据量来看。

RAM is volatile, i.e. data stored in it is lost when we switch off the computer or if there is a power failure. Hence, a backup Uninterruptible Power System (UPS) is often used with computers. RAM is small, both in terms of its physical size and in the amount of data it can hold.

RAM 分为两种类型——

RAM is of two types −

Static RAM (SRAM)
Dynamic RAM (DRAM)

Static RAM (SRAM)

static 一词表示只要有电力供应，存储器就可以保留其内容。但是，由于易失性，断电时数据会丢失。SRAM 芯片使用 6 晶体管矩阵，没有电容器。晶体管不需要电源来防止泄漏，因此不需要定期刷新 SRAM。

The word static indicates that the memory retains its contents as long as power is being supplied. However, data is lost when the power gets down due to volatile nature. SRAM chips use a matrix of 6-transistors and no capacitors. Transistors do not require power to prevent leakage, so SRAM need not be refreshed on a regular basis.

矩阵中有额外的空间，因此与用于相同存储空间的 DRAM 相比，SRAM 使用的芯片更多，这使得制造成本更高。因此，SRAM 被用作高速缓存，并且具有非常快的访问速度。

There is extra space in the matrix, hence SRAM uses more chips than DRAM for the same amount of storage space, making the manufacturing costs higher. SRAM is thus used as cache memory and has very fast access.

Characteristic of Static RAM

Long life
No need to refresh
Faster
Used as cache memory
Large size
Expensive
High power consumption

Dynamic RAM (DRAM)

与 SRAM 不同，DRAM 必须连续被 refreshed 以维护数据。这是通过将内存置于刷新电路上来完成的，该刷新电路每秒重写数据数百次。DRAM 用于大部分系统内存，因为它便宜且小巧。所有 DRAM 都由存储晶胞组成，每个存储晶胞由一个电容器和一个晶体管组成。

DRAM, unlike SRAM, must be continually refreshed in order to maintain the data. This is done by placing the memory on a refresh circuit that rewrites the data several hundred times per second. DRAM is used for most system memory as it is cheap and small. All DRAMs are made up of memory cells, which are composed of one capacitor and one transistor.

Characteristics of Dynamic RAM

Short data lifetime
Needs to be refreshed continuously
Slower as compared to SRAM
Used as RAM
Smaller in size
Less expensive
Less power consumption

Computer - Read Only Memory

ROM 代表 Read Only Memory 。我们只能从中读取但不能写入的内存。此类内存是非易失性的。信息在制造过程中永久存储在这些存储器中。ROM 存储启动计算机所需的操作说明。此操作称为 bootstrap 。ROM 芯片不仅用于计算机，还用于其他电子产品，如洗衣机和微波炉。

ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it. This type of memory is non-volatile. The information is stored permanently in such memories during manufacture. A ROM stores such instructions that are required to start a computer. This operation is referred to as bootstrap. ROM chips are not only used in the computer but also in other electronic items like washing machine and microwave oven.

现在让我们讨论一下各种类型的 ROM 及其特性。

Let us now discuss the various types of ROMs and their characteristics.

MROM (Masked ROM)

最早的 ROM 是硬连线设备，其中包含预先编程的一组数据或说明。这类 ROM 被称为屏蔽 ROM，价格低廉。

The very first ROMs were hard-wired devices that contained a pre-programmed set of data or instructions. These kind of ROMs are known as masked ROMs, which are inexpensive.

PROM (Programmable Read Only Memory)

PROM 是一种只读存储器，用户只能修改一次。用户购买一个空白的 PROM，并使用 PROM 程序输入所需的内容。在 PROM 芯片内部，有一些小保险丝会在编程过程中被烧断。它只能编程一次，并且不可擦除。

PROM is read-only memory that can be modified only once by a user. The user buys a blank PROM and enters the desired contents using a PROM program. Inside the PROM chip, there are small fuses which are burnt open during programming. It can be programmed only once and is not erasable.

EPROM (Erasable and Programmable Read Only Memory)

通过将 EPROM 暴露于紫外线下长达 40 分钟的时间，可以擦除 EPROM。通常，EPROM 擦除器可以实现此功能。在编程期间，电荷被困在绝缘栅极区域中。该电荷保持超过 10 年，因为电荷没有泄漏路径。要清除该电荷，紫外线会穿过石英晶体窗口（盖）。这种紫外线照射会消散电荷。在正常使用中，石英盖用贴纸密封。

EPROM can be erased by exposing it to ultra-violet light for a duration of up to 40 minutes. Usually, an EPROM eraser achieves this function. During programming, an electrical charge is trapped in an insulated gate region. The charge is retained for more than 10 years because the charge has no leakage path. For erasing this charge, ultra-violet light is passed through a quartz crystal window (lid). This exposure to ultra-violet light dissipates the charge. During normal use, the quartz lid is sealed with a sticker.

EEPROM (Electrically Erasable and Programmable Read Only Memory)

EEPROM 可通过电气方式编程和擦除。它可以被擦除和重新编程大约一万次。擦除和编程都需要大约 4 到 10 毫秒（毫秒）。在 EEPROM 中，任何位置都可以被选择性地擦除和编程。可以一次擦除一个字节的 EEPROM，而不是擦除整个芯片。因此，重新编程的过程是灵活的，但很慢。

EEPROM is programmed and erased electrically. It can be erased and reprogrammed about ten thousand times. Both erasing and programming take about 4 to 10 ms (millisecond). In EEPROM, any location can be selectively erased and programmed. EEPROMs can be erased one byte at a time, rather than erasing the entire chip. Hence, the process of reprogramming is flexible but slow.

Advantages of ROM

ROM 的优点如下 −

The advantages of ROM are as follows −

Non-volatile in nature
Cannot be accidentally changed
Cheaper than RAMs
Easy to test
More reliable than RAMs
Static and do not require refreshing
Contents are always known and can be verified

Computer - Motherboard

主板作为一个单一平台将计算机的所有部件连接在一起。它通过电缆或直接连接 CPU、内存、硬盘驱动器、光驱、显卡、声卡和其他端口和扩展卡。它可以被认为是计算机的主干。

The motherboard serves as a single platform to connect all of the parts of a computer together. It connects the CPU, memory, hard drives, optical drives, video card, sound card, and other ports and expansion cards directly or via cables. It can be considered as the backbone of a computer.

Features of Motherboard

主板具有以下特点——

A motherboard comes with following features −

Motherboard varies greatly in supporting various types of components.
Motherboard supports a single type of CPU and few types of memories.
Video cards, hard disks, sound cards have to be compatible with the motherboard to function properly.
Motherboards, cases, and power supplies must be compatible to work properly together.

Popular Manufacturers

以下是主板的热门制造商。

Following are the popular manufacturers of the motherboard.

Intel
ASUS
AOpen
ABIT
Biostar
Gigabyte
MSI

Description of Motherboard

主板安装在机箱内，并通过预先钻好的孔用小螺丝牢固地固定。主板包含用于连接所有内部组件的端口。它为 CPU 提供一个插槽，而对于内存，通常提供一个或多个插槽。主板提供端口以通过带状电缆连接软盘驱动器、硬盘驱动器和光盘驱动器。主板带有风扇和专为电源供应设计的特殊端口。

The motherboard is mounted inside the case and is securely attached via small screws through pre-drilled holes. Motherboard contains ports to connect all of the internal components. It provides a single socket for CPU, whereas for memory, normally one or more slots are available. Motherboards provide ports to attach the floppy drive, hard drive, and optical drives via ribbon cables. Motherboard carries fans and a special port designed for power supply.

主板前面有一个外围卡插槽，可用于将显卡、声卡和其他扩展卡连接到主板。

There is a peripheral card slot in front of the motherboard using which video cards, sound cards, and other expansion cards can be connected to the motherboard.

在左侧，主板带有许多端口，用于连接显示器、打印机、鼠标、键盘、扬声器和网络电缆。主板还提供 USB 端口，允许以即插即用方式连接兼容设备。例如，U 盘、数码相机等。

On the left side, motherboards carry a number of ports to connect the monitor, printer, mouse, keyboard, speaker, and network cables. Motherboards also provide USB ports, which allow compatible devices to be connected in plug-in/plug-out fashion. For example, pen drive, digital cameras, etc.

Computer - Memory Units

存储单元中可存储的数据量为存储单位。这种存储容量是按字节表示的。

Memory unit is the amount of data that can be stored in the storage unit. This storage capacity is expressed in terms of Bytes.

下表解释了主存储器存储单位 -

The following table explains the main memory storage units −

S.No.	Unit & Description
1	Bit (Binary Digit) A binary digit is logical 0 and 1 representing a passive or an active state of a component in an electric circuit.
2	Nibble A group of 4 bits is called nibble.
3	Byte A group of 8 bits is called byte. A byte is the smallest unit, which can represent a data item or a character.
4	Word A computer word, like a byte, is a group of fixed number of bits processed as a unit, which varies from computer to computer but is fixed for each computer. The length of a computer word is called word-size or word length. It may be as small as 8 bits or may be as long as 96 bits. A computer stores the information in the form of computer words.

下表列出了一些较高的存储单位 −

The following table lists some higher storage units −

S.No.	Unit & Description
1	Kilobyte (KB) 1 KB = 1024 Bytes
2	Megabyte (MB) 1 MB = 1024 KB
3	GigaByte (GB) 1 GB = 1024 MB
4	TeraByte (TB) 1 TB = 1024 GB
5	PetaByte (PB) 1 PB = 1024 TB

Computer - Ports

端口是外部设备可以连接到计算机的物理扩展坞。它也可以是程序扩展坞，信息可以通过它从程序流向计算机或通过 Internet。

A port is a physical docking point using which an external device can be connected to the computer. It can also be programmatic docking point through which information flows from a program to the computer or over the Internet.

Characteristics of Ports

端口具有以下特点： −

A port has the following characteristics −

External devices are connected to a computer using cables and ports.
Ports are slots on the motherboard into which a cable of external device is plugged in.
Examples of external devices attached via ports are the mouse, keyboard, monitor, microphone, speakers, etc.

现在，让我们讨论一些重要的端口类型 −

Let us now discuss a few important types of ports −

Serial Port

Used for external modems and older computer mouse
Two versions: 9 pin, 25 pin model
Data travels at 115 kilobits per second

Parallel Port

Used for scanners and printers
Also called printer port
25 pin model
IEEE 1284-compliant Centronics port

PS/2 Port

Used for old computer keyboard and mouse
Also called mouse port
Most of the old computers provide two PS/2 port, each for the mouse and keyboard
IEEE 1284-compliant Centronics port

Universal Serial Bus (or USB) Port

It can connect all kinds of external USB devices such as external hard disk, printer, scanner, mouse, keyboard, etc.
It was introduced in 1997.
Most of the computers provide two USB ports as minimum.
Data travels at 12 megabits per seconds.
USB compliant devices can get power from a USB port.

VGA Port

Connects monitor to a computer’s video card.
It has 15 holes.
Similar to the serial port connector. However, serial port connector has pins, VGA port has holes.

Power Connector

Three-pronged plug.
Connects to the computer’s power cable that plugs into a power bar or wall socket.

Firewire Port

Transfers large amount of data at very fast speed.
Connects camcorders and video equipment to the computer.
Data travels at 400 to 800 megabits per seconds.
Invented by Apple.
It has three variants: 4-Pin FireWire 400 connector, 6-Pin FireWire 400 connector, and 9-Pin FireWire 800 connector.

Modem Port

Connects a PC’s modem to the telephone network.

Ethernet Port

Connects to a network and high speed Internet.
Connects the network cable to a computer.
This port resides on an Ethernet Card.
Data travels at 10 megabits to 1000 megabits per seconds depending upon the network bandwidth.

Game Port

Connect a joystick to a PC
Now replaced by USB

Digital Video Interface, DVI port

Connects Flat panel LCD monitor to the computer’s high-end video graphic cards.
Very popular among video card manufacturers.

Sockets

Sockets connect the microphone and speakers to the sound card of the computer.

Computer - Hardware

硬件代表计算机的物理和有形组件，即可以看到和触摸到的组件。

Hardware represents the physical and tangible components of a computer, i.e. the components that can be seen and touched.

硬件的示例如下：

Examples of Hardware are the following −

Input devices − keyboard, mouse, etc.
Output devices − printer, monitor, etc.
Secondary storage devices − Hard disk, CD, DVD, etc.
Internal components − CPU, motherboard, RAM, etc.

Relationship between Hardware and Software

Hardware and software are mutually dependent on each other. Both of them must work together to make a computer produce a useful output.
Software cannot be utilized without supporting hardware.
Hardware without a set of programs to operate upon cannot be utilized and is useless.
To get a particular job done on the computer, relevant software should be loaded into the hardware.
Hardware is a one-time expense.
Software development is very expensive and is a continuing expense.
Different software applications can be loaded on a hardware to run different jobs.
A software acts as an interface between the user and the hardware.
If the hardware is the 'heart' of a computer system, then the software is its 'soul'. Both are complementary to each other.

Computer - Software

软件是一组程序，旨在执行明确的功能。程序是一系列指令，其编写目的是解决特定问题。

Software is a set of programs, which is designed to perform a well-defined function. A program is a sequence of instructions written to solve a particular problem.

软件有两类：

There are two types of software −

System Software
Application Software

System Software

系统软件是一组旨在操作、控制和扩展电脑本身的处理能力的程序集合。系统软件通常由电脑制造商准备。这些软件产品包含用低级语言编写的程序，这些程序与硬件在非常基本的层面进行交互。系统软件充当硬件和最终用户之间的接口。

The system software is a collection of programs designed to operate, control, and extend the processing capabilities of the computer itself. System software is generally prepared by the computer manufacturers. These software products comprise of programs written in low-level languages, which interact with the hardware at a very basic level. System software serves as the interface between the hardware and the end users.

系统软件的一些示例包括操作系统、编译器、解释器、汇编器等。

Some examples of system software are Operating System, Compilers, Interpreter, Assemblers, etc.

系统软件一些最突出的特性列出如下：

Here is a list of some of the most prominent features of a system software −

Close to the system
Fast in speed
Difficult to design
Difficult to understand
Less interactive
Smaller in size
Difficult to manipulate
Generally written in low-level language

Application Software

应用程序软件产品旨在满足特定环境的特定需求。在计算机实验室中准备的所有软件应用程序都可以归类为应用程序软件。

Application software products are designed to satisfy a particular need of a particular environment. All software applications prepared in the computer lab can come under the category of Application software.

应用程序软件可能包含一个程序，例如，微软的记事本用于编写和编辑一些简单的文本。它也可以包含一个程序集合，通常称为软件包，这些程序共同工作来完成一项任务，例如，电子表格软件包。

Application software may consist of a single program, such as Microsoft’s notepad for writing and editing a simple text. It may also consist of a collection of programs, often called a software package, which work together to accomplish a task, such as a spreadsheet package.

应用程序软件的示例如下：

Examples of Application software are the following −

Payroll Software
Student Record Software
Inventory Management Software
Income Tax Software
Railways Reservation Software
Microsoft Office Suite Software
Microsoft Word
Microsoft Excel
Microsoft PowerPoint

应用程序软件的特性如下：

Features of application software are as follows −

Close to the user
Easy to design
More interactive
Slow in speed
Generally written in high-level language
Easy to understand
Easy to manipulate and use
Bigger in size and requires large storage space

Computer - Number System

当我们键入一些字母或单词时，计算机将其翻译成数字，因为计算机只能理解数字。计算机可以理解位置数字系统，其中只有几个符号称为数字，并且这些符号根据它们在数字中占据的位置表示不同的值。

When we type some letters or words, the computer translates them in numbers as computers can understand only numbers. A computer can understand the positional number system where there are only a few symbols called digits and these symbols represent different values depending on the position they occupy in the number.

可以使用以下方法确定数字中每个数字的值 −

The value of each digit in a number can be determined using −

The digit
The position of the digit in the number
The base of the number system (where the base is defined as the total number of digits available in the number system)

Decimal Number System

我们在日常生活中使用的数字系统是十进制数字系统。十进制数字系统有 10 个基础，因为它使用了从 0 到 9 的 10 个数字。在十进制数字系统中，小数点左侧的连续位置表示个位、十位、百位、千位等。

The number system that we use in our day-to-day life is the decimal number system. Decimal number system has base 10 as it uses 10 digits from 0 to 9. In decimal number system, the successive positions to the left of the decimal point represent units, tens, hundreds, thousands, and so on.

每个位置表示基础的特定指数（10）。例如，十进制数字 1234 由个位数字 4、十位数字 3、百位数字 2 和千位数字 1 组成。它的值可以写成

Each position represents a specific power of the base (10). For example, the decimal number 1234 consists of the digit 4 in the units position, 3 in the tens position, 2 in the hundreds position, and 1 in the thousands position. Its value can be written as

(1 x 1000)+ (2 x 100)+ (3 x 10)+ (4 x l)
(1 x 103)+ (2 x 102)+ (3 x 101)+ (4 x l00)
1000 + 200 + 30 + 4
1234

作为一名计算机程序员或 IT 专业人士，你应对计算机中经常使用的以下数字系统有所了解。

As a computer programmer or an IT professional, you should understand the following number systems which are frequently used in computers.

S.No.

Number System and Description

Binary Number System Base 2. Digits used : 0, 1

Octal Number System Base 8. Digits used : 0 to 7

Hexa Decimal Number System Base 16. Digits used: 0 to 9, Letters used : A- F

Binary Number System

二进制数字系统的特征如下 −

Characteristics of the binary number system are as follows −

Uses two digits, 0 and 1
Also called as base 2 number system
Each position in a binary number represents a 0 power of the base (2). Example 20
Last position in a binary number represents a x power of the base (2). Example 2x where x represents the last position - 1.

Example

二进制数字：101012

Binary Number: 101012

计算十进制当量 −

Calculating Decimal Equivalent −

Step

Binary Number

Decimal Number

Step 1

101012

1 x 24) + (0 x 23) + (1 x 22) + (0 x 21) + (1 x 2010

Step 2

101012

(16 + 0 + 4 + 0 + 1)10

Step 3

101012

2110

Note − 101012 通常写为 10101。

Note − 101012 is normally written as 10101.

Octal Number System

八进制数字系统的特征如下 −

Characteristics of the octal number system are as follows −

Uses eight digits, 0,1,2,3,4,5,6,7
Also called as base 8 number system
Each position in an octal number represents a 0 power of the base (8). Example 80
Last position in an octal number represents a x power of the base (8). Example 8x where x represents the last position - 1

Example

八进制数：125708

Octal Number: 125708

计算十进制当量 −

Calculating Decimal Equivalent −

Step

Octal Number

Decimal Number

Step 1

125708

1 x 84) + (2 x 83) + (5 x 82) + (7 x 81) + (0 x 8010

Step 2

125708

(4096 + 1024 + 320 + 56 + 0)10

Step 3

125708

549610

Note - 125708 通常写成 12570。

Note − 125708 is normally written as 12570.

Hexadecimal Number System

十六进制数系统的特性包括：

Characteristics of hexadecimal number system are as follows −

Uses 10 digits and 6 letters, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F
Letters represent the numbers starting from 10. A = 10. B = 11, C = 12, D = 13, E = 14, F = 15
Also called as base 16 number system
Each position in a hexadecimal number represents a 0 power of the base (16). Example, 160
Last position in a hexadecimal number represents a x power of the base (16). Example 16x where x represents the last position - 1

Example

十六进制数：19FDE16

Hexadecimal Number: 19FDE16

计算十进制当量 −

Calculating Decimal Equivalent −

Step

Binary Number

Decimal Number

Step 1

19FDE16

1 x 164) + (9 x 163) + (F x 162) + (D x 161) + (E x 16010

Step 2

19FDE16

1 x 164) + (9 x 163) + (15 x 162) + (13 x 161) + (14 x 16010

Step 3

19FDE16

(65536+ 36864 + 3840 + 208 + 14)10

Step 4

19FDE16

10646210

Note - 19FDE16 通常写成 19FDE。

Note − 19FDE16 is normally written as 19FDE.

Computer - Number Conversion

有许多方法或技术可用于将数字从一个基数转换为另一个基数。在本章中，我们将演示以下内容：

There are many methods or techniques which can be used to convert numbers from one base to another. In this chapter, we’ll demonstrate the following −

Decimal to Other Base System
Other Base System to Decimal
Other Base System to Non-Decimal
Shortcut method - Binary to Octal
Shortcut method - Octal to Binary
Shortcut method - Binary to Hexadecimal
Shortcut method - Hexadecimal to Binary

Decimal to Other Base System

Step 1 ——将要转换的十进制数除以新基数。

Step 1 − Divide the decimal number to be converted by the value of the new base.

Step 2 ——将步骤 1 中的余数作为新基数数的右数最末位数字（最低有效数字）。

Step 2 − Get the remainder from Step 1 as the rightmost digit (least significant digit) of the new base number.

Step 3 ——将前一次除法的商再除以新基数。

Step 3 − Divide the quotient of the previous divide by the new base.

Step 4 ——将步骤 3 中的余数记录为新基数数的下一个数字（向左）。

Step 4 − Record the remainder from Step 3 as the next digit (to the left) of the new base number.

重复步骤 3 和 4，从右向左取余数，直到步骤 3 中的商变成 0。

Repeat Steps 3 and 4, getting remainders from right to left, until the quotient becomes zero in Step 3.

这样得到的最后的余数就是新基数数的最高有效数字 (MSD)。

The last remainder thus obtained will be the Most Significant Digit (MSD) of the new base number.

Example

十进制数：2910

Decimal Number: 2910

计算二进制等价——

Calculating Binary Equivalent −

Step	Operation	Result	Remainder
Step 1	29 / 2	14	1
Step 2	14 / 2	7	0
Step 3	7 / 2	3	1
Step 4	3 / 2	1	1
Step 5	1 / 2	0	1

如步骤 2 和步骤 4 中所述，余数必须按逆序排列，这样第一个余数就变成最低有效数字 (LSD)，最后一个余数就变成最高有效数字 (MSD)。

As mentioned in Steps 2 and 4, the remainders have to be arranged in the reverse order so that the first remainder becomes the Least Significant Digit (LSD) and the last remainder becomes the Most Significant Digit (MSD).

十进制数：2910 = 二进制数：111012。

Decimal Number : 2910 = Binary Number : 111012.

Other Base System to Decimal System

Step 1 ——确定每个数字的列（位置）值（这取决于数字的位置和数制系统的基数）。

Step 1 − Determine the column (positional) value of each digit (this depends on the position of the digit and the base of the number system).

Step 2 ——将步骤 1 中得到的列值与位于相应列中的数字相乘。

Step 2 − Multiply the obtained column values (in Step 1) by the digits in the corresponding columns.

Step 3 − 计算第 2 步中所得乘积之和。和数即为十进制等值。

Step 3 − Sum the products calculated in Step 2. The total is the equivalent value in decimal.

Example

二进制数：111012

Binary Number: 111012

计算十进制当量 −

Calculating Decimal Equivalent −

Step

Binary Number

Decimal Number

Step 1

111012

1 x 24) + (1 x 23) + (1 x 22) + (0 x 21) + (1 x 2010

Step 2

111012

(16 + 8 + 4 + 0 + 1)10

Step 3

111012

2910

二进制数：111012 = 十进制数：2910

Binary Number : 111012 = Decimal Number : 2910

Other Base System to Non-Decimal System

Step 1 − 将原始数字转换为十进制数（以 10 为基）。

Step 1 − Convert the original number to a decimal number (base 10).

Step 2 − 将获得的十进制数转换为新的基数。

Step 2 − Convert the decimal number so obtained to the new base number.

Example

八进制数：258

Octal Number : 258

计算二进制等价——

Calculating Binary Equivalent −

Step 1 - Convert to Decimal

Step

Octal Number

Decimal Number

Step 1

258

2 x 81) + (5 x 8010

Step 2

258

(16 + 5)10

Step 3

258

2110

八进制数：258 = 十进制数：2110

Octal Number : 258 = Decimal Number : 2110

Step 2 - Convert Decimal to Binary

Step	Operation	Result	Remainder
Step 1	21 / 2	10	1
Step 2	10 / 2	5	0
Step 3	5 / 2	2	1
Step 4	2 / 2	1	0
Step 5	1 / 2	0	1

十进制数：2110 = 二进制数：101012

Decimal Number : 2110 = Binary Number : 101012

八进制数：258 = 二进制数：101012

Octal Number : 258 = Binary Number : 101012

Shortcut Method ─ Binary to Octal

Step 1 − 将二进制位分组为三组（从右侧开始）。

Step 1 − Divide the binary digits into groups of three (starting from the right).

Step 2 − 将每组三个二进制位转换为一位八进制数字。

Step 2 − Convert each group of three binary digits to one octal digit.

Example

二进制数：101012

Binary Number : 101012

计算八进制等价−

Calculating Octal Equivalent −

Step	Binary Number	Octal Number
Step 1	101012	010 101
Step 2	101012	28 58
Step 3	101012	258

二进制数：101012 = 八进制数：258

Binary Number : 101012 = Octal Number : 258

Shortcut Method ─ Octal to Binary

Step 1 − 将每个八进制数字转换为一位三位二进制数（在进行该转换时，可将八进制数字视为十进制数字）。

Step 1 − Convert each octal digit to a 3-digit binary number (the octal digits may be treated as decimal for this conversion).

Step 2 − 将所有所得二进制组（每组 3 位）合并为一个二进制数。

Step 2 − Combine all the resulting binary groups (of 3 digits each) into a single binary number.

Example

八进制数：258

Octal Number : 258

计算二进制等价——

Calculating Binary Equivalent −

Step	Octal Number	Binary Number
Step 1	258	210 510
Step 2	258	0102 1012
Step 3	258	0101012

八进制数：258 = 二进制数：101012

Octal Number : 258 = Binary Number : 101012

Shortcut Method ─ Binary to Hexadecimal

Step 1 − 将二进制数字分为四组（从右开始）。

Step 1 − Divide the binary digits into groups of four (starting from the right).

Step 2 − 将每组四个二进制数字转换为一个十六进制符号。

Step 2 − Convert each group of four binary digits to one hexadecimal symbol.

Example

二进制数：101012

Binary Number : 101012

计算十六进制等值 −

Calculating hexadecimal Equivalent −

Step	Binary Number	Hexadecimal Number
Step 1	101012	0001 0101
Step 2	101012	110 510
Step 3	101012	1516

二进制数：101012 = 十六进制数：1516

Binary Number : 101012 = Hexadecimal Number : 1516

Shortcut Method - Hexadecimal to Binary

Step 1 − 将每个十六进制数字转换为一个四位二进制数（在此转换中，十六进制数字可视为十进制数字）。

Step 1 − Convert each hexadecimal digit to a 4-digit binary number (the hexadecimal digits may be treated as decimal for this conversion).

Step 2 − 将所有结果二进制组（每组 4 位）组合成一个二进制数。

Step 2 − Combine all the resulting binary groups (of 4 digits each) into a single binary number.

Example

十六进制数：1516

Hexadecimal Number : 1516

计算二进制等价——

Calculating Binary Equivalent −

Step	Hexadecimal Number	Binary Number
Step 1	1516	110 510
Step 2	1516	00012 01012
Step 3	1516	000101012

十六进制数：1516 = 二进制数：101012

Hexadecimal Number : 1516 = Binary Number : 101012

Computer - Data and Information

Data 可定义为以正式的方式表示事实、概念或说明，应适用于人和电子机器进行通信、解释或处理。

Data can be defined as a representation of facts, concepts, or instructions in a formalized manner, which should be suitable for communication, interpretation, or processing by human or electronic machine.

使用字符来表示数据，例如字母（A-Z、a-z）、数字（0-9）或特殊字符（+、-、/、*、<、>、= 等）。

Data is represented with the help of characters such as alphabets (A-Z, a-z), digits (0-9) or special characters (+,-,/,*,<,>,= etc.)

What is Information?

Information 是组织或分类的数据，对接收者而言具有一些有意义的值。信息是用作依据制定决策和采取行动的处理过的数据。

Information is organized or classified data, which has some meaningful values for the receiver. Information is the processed data on which decisions and actions are based.

要让决策有意义，处理过的数据必须符合以下特征 −

For the decision to be meaningful, the processed data must qualify for the following characteristics −

Timely − Information should be available when required.
Accuracy − Information should be accurate.
Completeness − Information should be complete.

Data Processing Cycle

数据处理是人员或机器对数据进行重新构建或重新排序，以提高其有用性并为特定目的增加价值。数据处理包括以下基本步骤：输入、处理和输出。这三个步骤构成了数据处理周期。

Data processing is the re-structuring or re-ordering of data by people or machine to increase their usefulness and add values for a particular purpose. Data processing consists of the following basic steps - input, processing, and output. These three steps constitute the data processing cycle.

Input − In this step, the input data is prepared in some convenient form for processing. The form will depend on the processing machine. For example, when electronic computers are used, the input data can be recorded on any one of the several types of input medium, such as magnetic disks, tapes, and so on.
Processing − In this step, the input data is changed to produce data in a more useful form. For example, pay-checks can be calculated from the time cards, or a summary of sales for the month can be calculated from the sales orders.
Output − At this stage, the result of the proceeding processing step is collected. The particular form of the output data depends on the use of the data. For example, output data may be pay-checks for employees.

Computer - Networking

computer network 是多个计算机连接在一起以共享信息和资源的系统。

A computer network is a system in which multiple computers are connected to each other to share information and resources.

Characteristics of a Computer Network

Share resources from one computer to another.
Create files and store them in one computer, access those files from the other computer(s) connected over the network.
Connect a printer, scanner, or a fax machine to one computer within the network and let other computers of the network use the machines available over the network.

以下是建立计算机网络所需硬件的列表。

Following is the list of hardware’s required to set up a computer network.

Network Cables
Distributors
Routers
Internal Network Cards
External Network Cards

Network Cables

网线用于连接计算机。最常用的线缆是 5 类线 RJ-45。

Network cables are used to connect computers. The most commonly used cable is Category 5 cable RJ-45.

Distributors

计算机可以通过串口连接到另一台计算机，但如果我们需要连接多台计算机来产生网络，则此串行连接将无法工作。

A computer can be connected to another one via a serial port but if we need to connect many computers to produce a network, this serial connection will not work.

解决方案是使用一个中心体，其他计算机、打印机、扫描仪等可以连接到它，然后这个中心体将管理或分配网络流量。

The solution is to use a central body to which other computers, printers, scanners, etc. can be connected and then this body will manage or distribute network traffic.

Router

路由器是一种充当网络中计算机和其他设备之间中心点的设备。它配有称为端口的孔。计算机和其他设备通过网线连接到路由器。如今，路由器采用无线模式，可以通过该模式在不使用任何物理线缆的情况下连接计算机。

A router is a type of device which acts as the central point among computers and other devices that are a part of the network. It is equipped with holes called ports. Computers and other devices are connected to a router using network cables. Now-a-days router comes in wireless modes using which computers can be connected without any physical cable.

Network Card

网卡是计算机的必要组件，没有它，计算机无法通过网络连接。它也称为网络适配器或网络接口卡 (NIC)。大多数品牌计算机都预装了网卡。网卡有两种类型：内部和外部网卡。

Network card is a necessary component of a computer without which a computer cannot be connected over a network. It is also known as the network adapter or Network Interface Card (NIC). Most branded computers have network card pre-installed. Network cards are of two types: Internal and External Network Cards.

Internal Network Cards

主板有一个用于插入内部网卡的插槽。内部网卡有两种类型，第一种类型使用外围组件互连 (PCI) 连接，而第二种类型使用工业标准架构 (ISA)。需要网线来提供网络访问。

Motherboard has a slot for internal network card where it is to be inserted. Internal network cards are of two types in which the first type uses Peripheral Component Interconnect (PCI) connection, while the second type uses Industry Standard Architecture (ISA). Network cables are required to provide network access.

External Network Cards

外部网卡有两种类型：无线和基于 USB。无线网卡需要插入主板，但是不需要网线连接到网络。

External network cards are of two types: Wireless and USB based. Wireless network card needs to be inserted into the motherboard, however no network cable is required to connect to the network.

Universal Serial Bus (USB)

USB 网卡易于使用，并通过 USB 端口连接。计算机会自动检测 USB 网卡，并且可以自动安装支持 USB 网卡所需的驱动程序。

USB card is easy to use and connects via USB port. Computers automatically detect USB card and can install the drivers required to support the USB network card automatically.

Computer - Operating System

操作系统是一个具有以下特征的程序：

The Operating System is a program with the following features −

An operating system is a program that acts as an interface between the software and the computer hardware.
It is an integrated set of specialized programs used to manage overall resources and operations of the computer.
It is a specialized software that controls and monitors the execution of all other programs that reside in the computer, including application programs and other system software.

Objectives of Operating System

操作系统的目标如下：

The objectives of the operating system are −

To make the computer system convenient to use in an efficient manner.
To hide the details of the hardware resources from the users.
To provide users a convenient interface to use the computer system.
To act as an intermediary between the hardware and its users, making it easier for the users to access and use other resources.
To manage the resources of a computer system.
To keep track of who is using which resource, granting resource requests, and mediating conflicting requests from different programs and users.
To provide efficient and fair sharing of resources among users and programs.

Characteristics of Operating System

下面列出了一些最突出的操作系统特征：

Here is a list of some of the most prominent characteristic features of Operating Systems −

Memory Management − Keeps track of the primary memory, i.e. what part of it is in use by whom, what part is not in use, etc. and allocates the memory when a process or program requests it.
Processor Management − Allocates the processor (CPU) to a process and deallocates the processor when it is no longer required.
Device Management − Keeps track of all the devices. This is also called I/O controller that decides which process gets the device, when, and for how much time.
File Management − Allocates and de-allocates the resources and decides who gets the resources.
Security − Prevents unauthorized access to programs and data by means of passwords and other similar techniques.
Job Accounting − Keeps track of time and resources used by various jobs and/or users.
Control Over System Performance − Records delays between the request for a service and from the system.
Interaction with the Operators − Interaction may take place via the console of the computer in the form of instructions. The Operating System acknowledges the same, does the corresponding action, and informs the operation by a display screen.
Error-detecting Aids − Production of dumps, traces, error messages, and other debugging and error-detecting methods.
Coordination Between Other Software and Users − Coordination and assignment of compilers, interpreters, assemblers, and other software to the various users of the computer systems.

Computer - Internet and Intranet

在本章中，我们将了解什么是 Internet 和 Intranet，以及讨论两者之间的相似之处和不同之处。

In this chapter, we will see what is Internet and Intranet, as well as discuss the similarities and differences between the two.

Internet

它是一个相互连接的计算机网络的全球系统。它使用标准互联网协议 (TCP/IP)。互联网中的每台计算机都通过唯一的 IP 地址进行标识。IP 地址是一组唯一的数字（例如 110.22.33.114），用于标识计算机的位置。

It is a worldwide/global system of interconnected computer networks. It uses the standard Internet Protocol (TCP/IP). Every computer in Internet is identified by a unique IP address. IP Address is a unique set of numbers (such as 110.22.33.114) which identifies a computer’s location.

使用一个特殊的计算机 DNS（域名服务器）为 IP 地址提供名称，以便用户可以通过名称找到计算机。例如，DNS 服务器会将名称 https://www.tutorialspoint.com 解析为特定的 IP 地址，以唯一标识托管此网站的计算机。

A special computer DNS (Domain Name Server) is used to provide a name to the IP Address so that the user can locate a computer by a name. For example, a DNS server will resolve a name https://www.tutorialspoint.com to a particular IP address to uniquely identify the computer on which this website is hosted.

全球的每一个用户都可访问互联网。

Internet is accessible to every user all over the world.

Intranet

内联网是多个电脑连接在一起的系统。内联网中的电脑不会向内联网之外的世界公开。通常，每个组织都有自己的内联网架构，并且该组织的成员/员工可以访问自己的内联网的电脑。

Intranet is the system in which multiple PCs are connected to each other. PCs in intranet are not available to the world outside the intranet. Usually each organization has its own Intranet network and members/employees of that organization can access the computers in their intranet.

内联网中的每台电脑也由一个 IP 地址识别，在该内联网的电脑中，该地址唯一。

Each computer in Intranet is also identified by an IP Address which is unique among the computers in that Intranet.

Similarities between Internet and Intranet

Intranet uses the internet protocols such as TCP/IP and FTP.
Intranet sites are accessible via the web browser in a similar way as websites in the internet. However, only members of Intranet network can access intranet hosted sites.
In Intranet, own instant messengers can be used as similar to yahoo messenger/gtalk over the internet.

Differences between Internet and Intranet

Internet is general to PCs all over the world whereas Intranet is specific to few PCs.
Internet provides a wider and better access to websites to a large population, whereas Intranet is restricted.
Internet is not as safe as Intranet. Intranet can be safely privatized as per the need.

How to Buy a Computer?

在本章节中，我们将提供相关信息来帮助你逐个购买台式机。由于台式机具有很强的可自定义性，所以最好了解主要部件，然后访问制造商或零售商的商店或网站，而不是直接查看某些特定型号。

In this chapter, we will supply relevant information to help you buy a desktop on component by component basis. As desktops are highly customizable, so it is better to learn about the main parts and then visit the manufacturer or the retailer shop or site, instead of just looking at some specific model directly.

一些流行的台式机品牌有戴尔、联想、惠普和苹果。始终根据这些品牌台式机的规格和基本价格进行比较。

Popular desktop brands are Dell, Lenovo, HP and Apple. Always compare the desktops based on their specifications and base price.

Monitor

Size − It is the diagonal size of the LCD screen. Larger the area, bigger the picture screen. A bigger picture is preferable for movie watching and gaming. It will increase the productivity as well.
Resolution − This is the number of pixels on the screen. For example, 24inch display is 1920x1200 (width by length) and 22-inch display is 1680x1050. High resolution provides better picture quality and a nice gaming experience.
Inputs − Now-a-days monitors can accept inputs from cable as well apart from the computer. They can also have USB ports.
Stand − Some monitors come with adjustable stands while some may not.
Recommended − 24 Inch LCD.

Operating System

Operating System is the main software of the computer as everything will run on it in one form or other.
There are primarily three choices: Windows, Linux, Apple OS X.
Linux is free, however people generally do not use it for home purpose.
Apple OS X works only on Apple desktops.
Windows 7 is very popular among desktop users.
Most of the computers come pre-equipped with Windows 7 Starter edition.
Windows 8 is recently introduced and is available in the market.
Windows 7 and Windows 8 come in multiple versions from starter, home basic, home premium, professional, ultimate, and enterprise editions.
As the edition version increases, their features list and price increases.
Recommended − Windows 7 Home Premium.

Optical Drive (CD / DVD / Blu-ray)

Optical drive is the drive on a computer, which is responsible for using CD, DVD, and Blu-ray discs.
Now-a-days, DVD burners are industry standards.
DVD Burner can burn CD, DVD and play them.
DVD Burner is cheaper than Blu-ray drives.
Blu-ray drives can play HD movies but are costlier component.
Recommended − DVD Burner.

Memory

RAM is considered as Computer Memory as the performance of a computer is directly proportional to its memory and processor.
Today’s software and operating system require high memory.
Today commonly used RAM is DDR3, which operates at 1066Mhz.
As per Windows 7, 1 GB is the minimum RAM required to function properly.
Recommended − 4 GB.

Hard Drive

Hard disk is used for storage purpose. Higher the capacity, more data you can save in it.
Now-a-days computers are equipped with 500GB hard drive, which can be extended to 2TB.
Most hard drives in desktop operate at the standard performance speed of 7200RPM.
Recommended − 500GB.

CPU

Frequency (GHz) − This determines the speed of the processor. More the speed, better the CPU.
Cores − Now-a-days CPUs come with more than one core, which is like having more than one CPU in the computer. Programs which can take advantage of multi-core environment will run faster on such machines.
Brand − Intel or AMD. Both are equivalent. Intel is in lead.
Cache − Higher the L1, L2 cache, better the CPU performance.
Recommended − Intel Core i3-3225 3.30 GHz Processor.

Computer - Available Courses

如今，各种类型的课程由教育机构提供。以下是其中一些常见且重要的课程。

Nowadays, various types of courses are provided by educational institutions. Following are some of the common as well as important courses.

Course

Name

Duration (years)

Minimum Qualification

B.C.A

Bachelor of Computer Applications

10+2

P.G.D.C.A

Post Graduate Diploma in Computer Applications

Graduation

M.C.A

Master of Computer Applications

Graduation

B.Sc.(CS)

Bachelor of Science (Computer Science)

10+2

M.Sc.(CS)

Master of Science (Computer Science)

Graduation

B.Tech.(CSE)

Bachelor of Technology (Computer Science and Engineering)

10+2

B.Tech.(IT)

Bachelor of Technology (Information Technology)

10+2

M.Tech.(CSE)

Master of Technology (Computer Science and Engineering)

B.Tech / B.E.

M.Tech.(IT)

Master of Technology (Information Technology)

B.Tech / B.E

B.E.(CSE)

Bachelor of Engineering (Computer Science and Engineering)

10+2

B.E.(IT)

Bachelor of Engineering (Information Technology)

10+2

Diploma Courses

除了常规学位课程，计算机中心还提供短期课程（3 个月至 1 年）。有关计算机基础知识、编程语言培训、硬件培训和网络认证等主题的在线课程也越来越受欢迎。

Apart from regular degree courses, computer centers also provide short-term courses (from 3 months to 1 year). Online courses on topics such as Computer Basics, Programming Languages Training, Hardware Training, and Network Certifications are also gaining in popularity.