Chapter 1 The Basics of Computing

• What is a Computer • Types of Computers • Computer Hardware • Computer Software • Communication Networks

What is a Computer?

A computer is a device that accepts input, manipulates it under a sequence of instructions (a program) and produces an output. This process is called the “Information Processing Cycle.” The output can be the result of a calculation or just an acknowledgement of the input.

Input Processing Instructions Output

For example… …an abacus is a kind of computer…

…so is a Slide Rule…

…

and a Burrough’s Adding Machine… Advertisement from 1954

Handheld devices such as these are also computers…

However, we’re concerned with just 3 types of computers that are used for business information systems: • Mainframes • Minicomputers • Microcomputers

Mainframe Computers • industry term for a large computer “big iron” • modularized to reduce overhead • used in centralized computing environments • large-scale computing server • high volume • high overhead processing • used as large database servers Mainframes typically cost hundreds of thousands of dollars and are manufactured by companies such as Hitachi, IBM and Amdahl.

Diagram of a Simple Mainframe Configuration PC Workstations or terminals Cluster Controller Front-End Processor (FEP) Mainframe Cluster Controller

Minicomputers • smaller than a Mainframe • larger than a PC (Microcomputer) • have become the “mid-range” server • IBM’s AS/400 is an example IBM AS/400

Microcomputers • Personal Computers (PCs) • desktop computing and client-server applications • can serve both as a • • Intel Motorola client – IBM compatible and a server • are generally categorized by the CPU type – Apple / MacIntosh / Power PC • Sun - SPARC Microcomputers are what we think of as PCs. Although they cross the line at times,

Sun Microsystems

generally is thought to manufacture high-end PCs.

Basic Parts of a PC

Monitor Computer Case Keyboard Mouse

Components of a Computer A computer needs the following devices to function: • Input device(s) • Processing Unit • Output device(s) • Storage device(s) This is the computer’s hardware…it is tangible.

Input Devices Accept data for the computer to work with… • Keyboard • Mouse • Scanner • Microphone

Processing Unit The Central Processing Unit, or CPU, is the brains of the computer. It controls all activity and performs operations on data based on its instruction set . The CPU is made up of several major units as diagrammed below.

Processing Unit The CPU consists of these main elements: • Control Unit - executes the instructions as interpreted • Arithmetic / Logic Unit - performs mathematical and logical operations • Registers - serve as the short term memory for the ALU’s computations and provides some reserved space for certain functions • Clock Unit - generates pulses that determine the speed of instruction processing, the rate is measured in megahertz (Mhz)

Processing Unit The CPU has two main features: • Its speed measured in millions of instructions per second, or

MIPS

• Its

word size

is the number of bits the CPU can process at a time. An 32-bit processor manipulates 32 bits simultaneously.

System Memory A PC has three basic types of memory : • Cache memory that is built into the CPU (not the • CPU registers) called L1 or L2 cache Read Only Memory (ROM) that is used to “ boot ” the system (among other applications) • Random Access Memory (RAM) which is the main memory that acts like the workshop or desktop of the CPU

Output Devices The purpose of an output device is to present electronic data (and the results of our work) in a form that can be understood and used. For example, think how hard it would be to use a computer without a monitor.

Typical output devices on a PC are: • Monitor • Printer or Plotter • Speakers

Output Devices Monitors: • CRT – Cathode Ray Tube, like a Television • LCD – Liquid Crystal Display • TFT – Thin-Film Transistor Printers: • Laser printers • Inkjet • Thermal Wax • Dot-Matrix

Auxiliary Storage Devices These devices, also known as secondary storage, are where the PC stores data that must last from session to session. Basically speaking this is the permanent data storage.

Though they differ in their technologies and methods of storage, the result is the same; the PC can easily retrieve the stored data for use at a later time.

These components are many times referred to as Mass Storage devices.

Auxiliary Storage Devices Types of Auxiliary or Mass Storage devices are: • Floppy disk drive • Hard disk drive • Optical disks (Compact discs, DVD) • Zip drives • Jazz or Bernoulli drives • Tape drives • Flash memory

Computer Software Software is computer instructions (Programs) and data. Anything that is electronically stored on a computer storage device is considered software. It is intangible and exists only electronically.

Two general types of software: • System software • Application software

System Software Systems software are the programs that control the computer and manage its resources. Such as operating systems and system utilities.

Operating systems

perform the basic tasks of computing like managing the input and output of data and interpreting the instructions of the programs.

System Utility software

performs more basic functions such as file management or backup, but they must work under an operating system.

Operating System HEWL ETT P ACKARD

4 0 0 0 T

1 2 3

G A TE WAY 2000

V I V I T RO N The Operating system connects components and directs the flow of data.

System Software Examples of Operating systems: • Windows (XP, 2000, ME, 98, 95, 3.1, CE) • • • • DOS ( MS-DOS , DR-DOS , PC-DOS ) • Mac OS X • Unix ( Solaris , FreeBSD , SCO UNIX ) Linux Palm OS BeOS Operating systems are written to run on specific processors (platforms).

System Software Examples of Utility software: • Anti-virus software • Norton , McAfee , Sophos , Trend Micro • File Management • PKZip , WinZip , Norton SystemWorks • Disk Utilities • PartitionMagic , System Commander • Backup • Retrospect , Backup MyPC Utility software is written to run under specific operating systems.

Application Software Application software consists of programs that help you work and play on the computer. This category includes word processors, games, spreadsheets, drawing and other “productivity” programs. This is the bulk of all software written.

Application software is written to run under specific operating systems.

Application Software Examples of Application software: • Document Processing • Adobe Acrobat , WordPro , TextBridge • Graphics • Flash , CorelDraw , PaintShop Pro • Games • MS Flight Simulator , Tomb Raider • Programming • Kylix , CodeWarrior • Suites • StarOffice , WordPerfect Office , Office 2000 • Database Management • Oracle , SQL Server , MySQL

Communication Networks aka Computer Networks Two or more computers connected to share data and resources are “networked.” The simple idea behind computer networking is to allow users to access more information and give them access to devices not directly attached to their “local” system, such as printers or storage devices.

Computer Networks Two of the main types of computer networks are: • LAN - Local Area Network • WAN - Wide Area Network A

LAN

is comprised of computers located within close proximity, such as in an office or building. A

WAN

is a network of computers that are situated further apart, but still connected. Such a network might be of computers within a single state agency or of a multi-national corporation worldwide.

Computer Networks A PC must have a Network Interface Card installed to connect it to a network. The cards, frequently called “nics”, come installed in many new computers as they are also used for cable modem and DSL internet service.

The computers can be configured in several ways, the most popular of these “architectures” are peer-to-peer and client/server.

The first is a loose connection of local computers with no central authority, the later relies on a “server” to manage the network and its resources.

Peer-to-Peer Network Ethernet Hub

A peer-to-peer network requires the computers to be connected to each other by a network cable, usually an “unshielded twisted pair” cable known as “ CAT 5 ”. Connecting more then two computers require the use of a network hub as shown.

Client/Server Network Hub Network Server A client/server network uses a computer known as the server to manage the network and control access to resources. The computers can be connected using various types of cable including CAT 5, coaxial and fiber optical .

Computer Networks Local Area Networks are configured in 3 basic topologies . These are either the logical or physical way the computers are connected. Each connection on the network is known as a node .

These topologies are: • Star • Bus • Ring

Server A Star topology connects all the nodes directly to the server or to a connecting device such as a hub .

Server All nodes on a Bus topology are connected to a central line or backbone.

Server Nodes on a Ring topology are connected in a closed loop. This means that each node has two connections, one in and another out. Using this type of topology the data must travel through all the nodes.

Computer Network Software Computer networks use special operating systems and other system software to manage the network, its resources and its users. Network Operating Systems ( NOS ) should be very secure and robust to provide reliable network services.

Examples of such software are: • Windows 2000 Server • Novell NetWare • • Unix …too many flavors to link them all Linux

The Internet The Internet is a worldwide computer network.

Actually it is a loose collection of networks. There is no central control or authority, all cooperation is voluntary to a degree… Users access the Internet by using a network that is connected to a “backbone” usually through an Internet Service Provider ( ISP ). The real access path to the ‘net is through a

N

etwork

A

ccess

P

oint ( NAP ).

The World Wide Web The World Wide Web is a collection of computers connected via the Internet that support the use of documents written in

H

yper

T

ext

M

arkup

L

anguage ( HTML ).

The “web” uses the

H

yper

T

ext

T

ransfer

P

rotocol ( HTTP ) as the standard for the formatting and transmission of these documents.

Not every server on the ‘net uses HTTP, and therefore is not part of the Web.

The Internet is very large and diverse, there is no one method of access and there are many protocols used such as: • NNTP -

N

etwork

N

ews

T

ransfer

P

rotocol for newsgroups • SMTP -

S

imple

M

ail

T

ransfer

P

rotocol for sending • FTP e-mail

F

ile

T

ransfer

P

rotocol used for sending files

It’s a wonder it works so well, much less at all.

Hobbes' Internet Timeline

: http://info.isoc.org/guest/zakon/Internet/History/HIT.html