Computer Explained for beginners

1. Hardware

The physical components of a computer system are called hardware. The basic qualities of hardware are that they can be handled and that they cannot be changed easily. In a computer system, the Central Processing Unit, Keyboard and Monitor are considered its main hardware components, other hardware are basically identified as minor devices.

2. Software
The instructions given in sequence in order to operate a computer to achieve a particular aim are called computer software. There are several types of software depending on their applications. Let us take them into consideration in the course of software classification.

3. Firmware
The program required initially to boot up a computer system is called firmware. Since these firmware are incooperated in the process of manufacturing hardware, they cannot be easily changed later on.

For example, Read Only Memory (ROM) in a computer. Further, firmware are incooperated in washing mashines, microwave Ovens, Mobile phones, Ipods etc...

4. Liveware
Should one be engaged in handling a computer, at that moment, he or she is considered liveware.



Classification of computer hardware

The main types of computer hardware are input devices, Output devices, Memory devices, control and processing devices and communication devices. We shall be discussing these hardware separately later on.

Input Devices
Devices used to supply data to a computer system are input devices.
Eg: Keyboards, Pointing devices, Scanners, Microphones, Digital Cameras, and Webcam etc...

Keyboard
The keyboard is used to input letters, numbers, symbols and commands to a computer system. Although the keyboard can be considered be as an improved version of the normal typewriter keyboard its operation takes place electronically. A processor receives a unique electrical signal when the relevant key is pressed. The processor converts that signal to ASCII code and provides the relevant input to the computer system. Today both cable connected and wireless key boards are available in the market.

Pointing Devices
The main task of pointing devices is the opening of Icons created by pixels or pixel on the screen of a computer and the implementation of the related programs. For this purpose Mouse, Mouse pad, Touch screen, Touch pad, Track ball, Joystick etc. are example. In order to send signals to the processor through them, cables or light waves are used.

Scanner
The scanner is used to input text and pictures in a hard copy to a computer system. One special feature of this is the storing of both text and picture in image from in the computer memory. But if a scanner has Optical Character Reader facilities, then English letters like Times new Roman, Aerial are stored in the computer memory not in image form but in the letter form. Therefore, text can be easily edited.

Digital Camera
There are two types of cameras in terms of picture storage technology
1. Film Camera
2. Digital camera

Since images stored in the memory of a digital camera can be input to a computer, a digital camera is also an input device. Digital cameras also are of two types according to function, they are
1. Still digital camera
2. Movie digital camera

Various types of digital cameras are available in the market today. Also these cameras are found even in mobile phones.

Webcams
Webcams are a type of cameras used to broadcast moving pictures in digital form. With their arrival in the field
1. Individuals can be seen live in an internet telephone connection
2. Teleconferencing etc;
have turned a new page in communication technology. These webcams  can be purchased and connected externally to the computer. Similarly, there are laptops in the market with cams attached.

Output Devices
These devices are used to give the processed information and signals from the computer. Monitors, Printers and Speakers are some examples for them.

Monitor
This is called the computer screen. According to technology, two types of monitors are in use today.

1. CRT - Cathod Ray Tube Monitor
2. LCD - Liquid Crystal Display Monitor

It is necessary to identify the advantages and disadvantages before they are used. In general, it is essential to acquire knowledge about the characteristics of the monitors.

1. The number of pixels per unit in the screen.
2. The number of colors that can be displayed.
3. The degree of harmful radiation emitted.

Printer
This is used to transfer the soft copy in the computer into a hard copy. There are two types of printers such as Impact printers and non-impact printers. The impact printers are very noisy. 

Three types of printers are used today.

1. Dot Matrix printers (Impact printers)
2. Inkjet printers (Non-impact printers)
3. Bubble jet printers (Non-impact printers)
4. Laser Printers (Non-impact printers)

These printers use different technologies and the manner of supplying ink is also different. To use a printer, the following things should be taken into consideration.

1. The quality of the hard copy.
2. The cost for a copy.
3. The time spent on a copy.
4. Noise when in use.

Listening Devices
We will consider the devices used to listen to the sounds from the computer. These devices are of two types; such as the speakers and head set. Only the person who wears the headset can listen to the sounds from the computer.

Memory Devices
The devices used to store data and information for a short time or long time in a computer are called memory devices. These memory devices are of three types.

1. Random Access Memory (Internal)
2. Read Only Memory (Internal)
3. Backup Devices (External)

Random Access Memory
When a computer is started, the Operating System is input from the Hard Disk to the Random Access Memory. Before data are processed, the data and instructions are also retained temporarily in this RAM. It holds them in the memory until the power is available. These are called Readable and Writable Memories .

Read Only Memory
The Special Instructions necessary to boot up the computer is stored in this permanently by the manufacturer. These are called Read Only Memories. These ROMs are attached to the motherboard of the computer. This memory is only readable. The instructions stored in this are called firmware.

Backup Storage
Backup storage is the storage media that store data permanently and it is also called secondary memory. The data stores here can be retrieved again and again and can be edited too. For example Hard Disk, Compact Disc, Floppy Disketts, Pen Drives are some of them .
Their technologies and functions may vary.

Control and Processing Devices 
The two most essential tasks of the computer; such as calculations and controlling are done by  a semi conductor device attached to the motherboard. This is called the central processing unit or the processor. In the development of the computer the main consideration should be given to CPU when we consider the evolution of the CPU. It is important to consider the technology used, calculation speed, capacity, size and type. The speed of the CPU is called clock speed and is measured in MHz, GHz . The CPU consist of three parts.

1. Control Unit
2. Arithmetic and Logic Unit (ALU)
3. Register Arrays



Control Unit

• Controls all the functions of the computer system.
• Decodes the instructions in the memory.
• Sends signals to the relevant parts.

Arithmetic and Logic Unit

• Does all types of mathematical calculations
• Compares data

Register Array

• Temporarily stores data and instructions until they are sent to the logical unit.
• Stores process information until it is sent to the main memory

Communication Devices
There are many basic devices that link computer technology and communication technology in addition to the above devices such as the input devices, output devices, memory devices and control and processing devices.

Network Interface Card (NIC), Modem, Multiplexer. Bluetooth Adapter are some examples of them.

Computer Software Classification
A set of sequential instructions given to the computer system to carry out a specific task is called a software. Mainly, aomputer software are of two types.
 1. System Software
2. Application Software

System Software
System software can be classified into three according usage. They are 

1. Operating Saytems
2. Language Translators
3. Utility Software

Application Software
The software used by the user of the computer to fulfill necessities is called Application Software. Some examples are Word Processing Software, Spreadsheet Software and Data Base Management Software etc. Unlike system software, daily new application software are available in the market.

Copyrighted Software and Open Source Software
When considering the copyright of software there are two things that have to be discussed.
1. Copyrighted software
2. Open source softwarte

Copyrighted Software
The software that belong to a party who have the legal rights, are called Copyrighted Software. Only those who have a license from the copyrighted party can use change or distribute this software. This software has a legal binding. Some of the companies of this type are Microsoft, Macromedia, Adobe, etc.

Open Source Software
The software that does not have a copyright belongs to this category. This software legally allows the user to use, change and distribute it partially or completely. This software is also called Independent Software. 

History of the computer
The history of Information and Communication Technology can be divided into four main eras.

1. Pre mechanical era (before 1450)
2. Mechanical era (1450-1840)
3. Electromechanical era (1840-1940)
4. Electronic era (1940-to date)

• It is evident that the mathemetical calculating device, the Abacus had been used in China around 3000 BC.
• The first mechanical calculator, the Pascline was invented by Blaise Pascal in 1642. It could perform only addition and substraction.
• The German scientist Gottfried Wilhelm Von Liebnitz improved the Pascaline to state thar it could be used to multiply and divide also. The concept of punched card had been used for this purpose.
• In 1880 Charles Babage invented the Analitical Engine that could carry out mathemetical operations and also store data. It was Charles Babage who presented the concept of Input, Process and Output that is used in modern computers, for the first time. Therefore, some consider him "The father of the computer". Lady Ada Augesta Lovelace who assisted him is regarded the first programmer. 
• The invention of the "Electronic valve" by Forrest in 1906 laid the foundation to modern computer technology.
• The automatic sequence calculator or otherwise Mark 1 was the first automatic computer invented by Howard Aiken, professor of Havard University in 1939.
• ENIAC (Electronic Numerical Integrator and Calculator) invented in 1946 is considered the first electronic Digital computer.
• EDVAC (Electronic Discrete Variable Automatic Computer) Invented in 1948, is considered the first digital computer that could store programs.
• The first generation of computers ended with the invention of the transistors in 1947. The period 1940-1956 is considered the first generation of computers.
• Computers built using transistors are considered 2nd generation computers.In 1964, after the invention of integrated circuits which were made out of a collection of transistors, computers became small in size, low in price and also it had a high speed. These computers which were made out of ICs are called 3rd generation computers (1964-1971). In course of time with the advancement of technology silicon chip which was made out of them and of ICs was invented. As a result LSI (Large Scale Integration) and VLSI (Very Large Scale Integration) chips were found. 

• During this period, with the development of technology, where thousands of integrated circuits were detached to form a single silicon chip and the Micro Processor was born. While the computers built using them increased in speed and efficiency, there was a drop in size and cost.
• MIT built the ALTAIR 8800 computer in 1975. In 1981 the first personal computer IBM-PC was built by IBM. Following this, the Apple computer Company built the Macintosh Computer in 1984 setting a landmark in the history of the computer.
• It was possible to build the computer of the fourth generation in such a manner that it was attractive to the user and also incorporated Graphical User Interface (GUI)
• The Apple and IBM companies became quite popular in the development of personal computers. The processor provider of the IBM Company was the Intel Company. 
• The other organizations that produce processors are Intel, Cyrix, IDT, AMD, and Motorola.

Future directions of computer technology
The anticipation of present day scientists is to build a computer that perform functions of an intelligent human. In computer science this particular field is called Artificial Intelligence. Man has the ability to involve himself in complex activities like concentrating on different traits of thought at the same time, and to distinguish between different voices. Robot technology and the construction of automatic vehicles based on artificial intelligence, are technologies already in place. 

While the concept of the molecular computer / DNA computers and biological computers are already in process they will be a reality in the future. Further, the development of a quantum computer by 2015 is one aim of the scientists. These are considered objectives of the fifth generation computers.

Evolution of the processors

The Transistors
Before the invention of transistors, electronic valves were used in the construction of computers. Since a lot of heat was emitted problems arose due to burning out of valves. A circuit built by assembling several transistors was called a chip. By using chips it was possible to overcome the above problems. In this chip there are a large number of circuits built by using semiconductor technology.

Specification of a processor

Bus
The physical path along which data travels as signals within the components of a computer or within the components between computers is called a bus.
There are three main varieties of bus on the motherboard.

1. Data Bus
The bus carrying Data from one place to another is called a data bus.

2. Address Bus
A particular location is selected in order to read the data in the memory or write data into memory. The address of this location is known as the address bus.

3. Control Bus
The location where signals of the Arithmetic and logic unit are stored temporarily is called registers.

Clock speed of a CPU
The speed at which instructions provided to a processor implemented, is called the clock speed of the CPU. The CPU of a modern computer is measured in MHz or Ghz

Word Size
The number of bits in a machine language word used in a computer is called its size or its word length.

Classification of computers

There are several ways of classifying computers
1. According to size 
2. According to technology used
3.According to purpose of use

1. Classification of computers According to size

• Super Computers
• Mainframe Computers
• Mini Computers
• Micro Computers

2. Classification of computers According to technology used

• Digital Computers
• Analog Computers
• Hybrid Computers

3. Classification of computers According to purpose of use

• General Purpose
• Special Purpose
• Personal Computers that fall into the category of Micro computers are as follows.
• Desktop Computers
• Workstations
• Laptop Computers
• Palmtop Computers
• Notebook Computers
• Personal Digital Assistant (PDA) or Digital Diary
• Pocket Computers