Chapter One

Introduction

1-1 Computer Definition
1-2 Computer Characteristics
1-3 Classification of Electronic Computer
1-4 Computer Development
1-5 Components of Computer System


 
Introduction to computers

1-1Computer Definition:

• "Computer" is a word derived from "Compute" which means to calculate. "Computer" is defined as an electronic computing device, characterized by high speed and accuracy. It can handle data processing, storing, and retrieval following a set of instructions and orders to get the required results.

• "Computer" is one of the electronic devices which can perform a set of integrated and consequent operations on a set of input data. Computer can process these operations according to a set of instructions and orders which are logically and algorithmically coordinated to solve a specific problem to get useful information and results. The instructions and orders are called "Statements", which are consequently called a program. The person who designs this program called programmer.

• "Computer" is a set of electronic components called Hardware and controlled by a set of operating systems called Software.

1-2 Computer Characteristics:

1. Quick performance.
2. Quick data input and information retrieval.
3. Ability to store data.
4. Accurate results, which depend on  the accuracy of data input.
5. Reducing human role, in particular in mechanically run factories.
6. Quick processing of arithmetic's and logic operations.
7. Continuous and persistent workability.
8. Available a lot of software and applicable programs that facilitate computer accessibility without need to study computer science.
9. Prompt decision making to find proper and at most solutions for specifics question.
10. Communicability through computer networks with other computers to exchange data and information.

1-3 Classification of Electronic Computer:

Computers are classified according to:

1- The ability of storage and performance efficiency:

•Super Computer:
Supercomputers are the most powerful computers. They are used for problems requiring complex calculations.
Because of their size and expense, supercomputers are relatively rare.
Supercomputers are used by universities, government agencies, and large businesses.

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Figure 1-1 Super Computer

•Mainframe Computers:
Mainframe computers can support hundreds or thousands of users, handling massive amounts of input, output, and storage.Mainframe computers are used in large organizations where many users need access to shared data and programs. Mainframes are also used as e-commerce servers, handling transactions over the Internet.

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Figure 1-2 Mainframe

•Minicomputers:
Minicomputers are smaller than mainframes but larger than microcomputers. Minicomputers usually have multiple terminals. Minicomputers may be used as network servers and Internet servers.

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Figure 1-3 Minicomputer

•Microcomputers:
Microcomputers are more commonly known as personal computers. The term "PC" is applied to IBM-PCs or compatible computers. Full-size desktop computers are the most common type of PC. Notebook (laptop) computers are used by people who need the power of a desktop system, but also portability. Handheld PCs (such as PDAs) lack the power of a desktop or notebook PC, but offer features for users who need limited functions and small size.

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Figure 1-5 Laptop Figure 1-4 Microcomputer

2- The operating method:

•Digital computer:
electronic devices that process discrete data and calculations using digits represented by number forms in high speed. In this sense, Binary system is used to represent the values of variables and quantities. This kind is the commonest and the most accurate since it can be programmed and used in a rarity of fields.

Analogue computers:
electronic devices work on waves principle. They are used in specific to measure continuous flow of data which can expressed in tangible quantities such as atmospheric pressure, temperature, and voltage.
They are used in scientific and engineering fields to give round results.

Hybrid Computers:
devices that incorporate the qualities of the previous two types ( digital and analogue ). They are used in scientific fields processing necessary data from both kinds. They are characterized by their digital processing the ability to store data, high accuracy, the ability to create arithmetic functions (correlations). Their disadvantages  high cost, inevitable errors, and overlapped programming.

3- The purposes:

•General Purpose Computers:
designed for multipurpose functions such as salaries and wages , and processing the storage operation in factories and establishments, analyze sales for they are flexible to assure efficiency , commercial , scientific, medical, and engineering fields.

Special Purpose Computers:
 designed for specific functions such as early alarm devise and computers used in industrial operations , which may be microcomputers or minicomputer. 

1-4 Computer Development:

Computer development relied upon the following basic factors:
1. Increasing computer speed.
2. Decreasing computer size.
3. Decreasing computer cost.
4. Enhancing result accuracy.
5. Increasing storage capacity.
6. Facilitating computer accessibility.

1- First Generation:

• Emerged in 1940's and mid 1950's.
• Consisted of vacuum tube based  logical and electronic circuits.
• Used magnetic drums for internal storage and magnetic tape for external storage.
• Relatively slow.
• Huge size of the computer.
• System failure due high temperature produce by vacuums.
• Very limited memory capacity.
• Use machine language in programming.
• Use punched cards to store data.
• Include ENIAC, EDVAC, and EDSAC as First Computers, then UNIVAC.

2- Second Generation:

• Emerged in mid 1950's and 1960's
• built on Transistors and small sized circuits with high operating efficiency.
• Using magnetic circuits for memory.
• Using  Hardisk for every storing and retrieval of data.
• Using new high level languages such as Fortran, and Cobol.

3- Third generation:

• Emerged in 1960's:
• Use small scale integrated circuits, followed by medium scale integrated, resulting in small size and high memory capacity and accurate performance.
• Distinguished high performance speed.
• Resulted in emergence of microcomputers and multiprocessors.
• Developed operating systems to improve effectiveness and performance, such as multiprogramming system.
• emergence of new high level languages such as Basic and Pascal.
• Improvement of input and output devices.

4- Fourth generation:

• Emerged in 1970's and 1980's
• Use semiconductors to develop large scale integrated circuit and very large scale integrated circuits called microprocessors.
• Very high speed performance.
• Emergence of  Personal Computers and microcomputers.
• Emergence of new operating systems such as Real time systems.
• Emergence of Floppy disks.

1-5 Components of Computer System:

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Figure 1-6 The four basic components of computer system

Computer system is composed of hardware, software, data, and users.
1. Hardware:
A computer's hardware consists of electronic devices; the parts you can see and touch.The term "device" refers to any piece of hardware used by the computer, such as a keyboard, monitor, modem, mouse, etc.

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Figure 1-7 Hardware inside the computer

2. Software:
Software – also called programs – consists of organized sets of instructions for controlling the computer. Some programs exist for the computer's use, to help it manage its own tasks and devices. Other programs exist for the user, and enable the computer to perform tasks for you, such as creating documents.

3. Data:
Data consists of raw facts, which the computer can manipulate and process into information that is useful to people. Computerized data is digital, meaning that it has been reduced to digits, or numbers. The computer stores and reads all data as numbers. Although computers use data in digital form, they convert data into forms that people can understand, such as text, numerals, sounds, and images.

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Figure 1-8 Electronic Data Processing

4. Users:
People are the computer's operators, or users. either the programmer who designs the program in programming languages, the end user who uses applicable program's in managing daily terms, or the administrator who management computer networks. Some types of computers can operate without much intervention from people, but personal computers are designed specifically for use by people.


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