1 Introduction to Computers. 2 25 Chapter Goals Describe the history of computer hardware and software Describe the changing role of the computer user.

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Introduction to Computers

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Chapter Goals

• Describe the history of computer hardware and software

• Describe the changing role of the computer user

• Distinguish between systems programmers and applications programmers

• Distinguish between computing as a tool and computing as a discipline

• List the basic components of a computer system

• Understand what a Computer Program is• List the Programming Life-Cycle Phases

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Hardware The physical elements of a computing system (printer, circuit boards, wires, keyboard…)

Software The programs that provide the instructions for a computer to execute

Computing Systems

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Abacus An early device to record numeric values

Blaise Pascal Mechanical device to add, subtract, divide & multiply

Joseph Jacquard Jacquard’s Loom, the punched card

Charles BabbageAnalytical Engine

Early History of Computing

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Ada LovelaceFirst ProgrammerAlan TuringTuring Machine, Artificial Intelligence Testing

Harvard Mark I, ENIAC, UNIVAC IEarly computers launch new era in mathematics, physics, engineering and economics

Early History of Computing

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Vacuum TubesLarge, not very reliable, generated a lot of heat

Magnetic Drum Memory device that rotated under a read/write head

Card Readers Magnetic Tape DrivesSequential auxiliary storage devices

First Generation Hardware (1951-1959)

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TransistorReplaced vacuum tube, fast, small, durable, cheap

Magnetic CoresReplaced magnetic drums, information available instantly

Magnetic DisksReplaced magnetic tape, data can be accessed directly

Second Generation Hardware (1959-1965)

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Integrated CircuitsReplaced circuit boards, smaller, cheaper, faster, more reliable.

TransistorsNow used for memory construction

Terminal An input/output device with a keyboard and screen

Third Generation Hardware (1965-1971)

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Large-scale IntegrationGreat advances in chip technology

PCs, the Commercial Market, WorkstationsPersonal Computers were developed as new companies like Apple and Atari came into being. Workstations emerged.

Fourth Generation Hardware (1971-?)

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Parallel ComputingComputers rely on interconnected central processing units that increase processing speed.

Networking

ARPANET and LANs Internet

Parallel Computing and Networking

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Machine LanguageComputer programs were written in binary (1s and 0s)

Assembly Languages and translatorsPrograms were written in artificial programming languages and were then translated into machine language

Programmer ChangesProgrammers divide into application programmers and systems programmers

First Generation Software (1951-1959)

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High Level LanguagesUse English-like statements and make programming easier. Fortran, COBOL, Lisp are examples.

High-LevelLanguages

Assembly LanguageMachine

Language

Second Generation Software (1959-1965)

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Third Generation Software (1965-1971)

• Systems Software– utility programs, – language translators, – and the operating system, which decides which

programs to run and when.

• Separation between Users and Hardware

Computer programmers began to write programs to be used by people who did not know how to program

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Application Package

Systems Software

High-Level Languages

Assembly Language

Machine Language

Third Generation Software (1965-1971)

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Structured ProgrammingPascal, C, C++

New Application Software for UsersSpreadsheets, word processors, database management systems

Fourth Generation Software (1971-1989)

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MicrosoftThe Windows operating system, and other Microsoft application programs dominate the market

Object-Oriented DesignBased on a hierarchy of data objects (i.e. Java)

World Wide WebAllows easy global communication through the Internet

New UsersToday’s user needs no computer knowledge

Fifth Generation Software (1990- present)

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Programmer / User

Applications Programmer(uses tools)

User with No Computer Background

Systems Programmer(builds tools)

Domain-Specific Programs

Computing as a Tool

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Computing as a Discipline

• What can be (efficiently) automated?

• Four Necessary Skills1. Algorithmic Thinking

2. Representation

3. Programming

4. Design

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Is Computer Science a mathematical, scientific, or engineering discipline?

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What do you think?

Computing as a Discipline

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Systems Areas of Computer Science

• Algorithms and Data Structures

• Programming Languages

• Architecture

• Operating Systems

• Software Methodology and Engineering

• Human-Computer Communication

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Application Areas of Computer Science

• Numerical and Symbolic Computation

• Databases and Information Retrieval

• Artificial Intelligence and Robotics

• Graphics

• Organizational Informatics

• Bioinformatics

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Computer Components-- Hardware

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Memory Unit

• is an ordered sequence of storage cells, each capable of holding a piece of information

• each cell has its own unique address

• the information held can be input data, computed values, or your program instructions.

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Memory Unit

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RAM and ROM

• RAM stands for Random Access Memory– Inherent in the idea of being able to access each

location is the ability to change the contents of each location

• ROM stands for Read Only Memory– The contents in locations in ROM cannot be changed

• RAM is volatile, ROM is not– This means that RAM does not retain its bit

configuration when the power is turned off, but ROM does

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Secondary Storage Devices

• Because most of main memory is volatile and limited, it is essential that there be other types of storage devices where programs and data can be stored when they are no longer being processed

• Secondary storage devices can be installed within the computer box at the factory or added later as needed

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Magnetic Tape

• The first truly mass auxiliary storage device was the magnetic tape drive

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Magnetic Disks• A read/write head travels across a spinning

magnetic disk, retrieving or recording data

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Compact Disks

• A CD drive uses a laser to read information stored optically on a plastic disk

• CD-ROM is Read-Only Memory

• DVD stands for Digital Versatile Disk

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Peripherals

• are input, output, or auxiliary storage devices attached to a computer

– Input Devices include keyboard and mouse.

– Output Devices include printers, video display, LCD screens.

– Auxiliary/Secondary Storage Devices include disk drives, scanners, CD-ROM and DVD-ROM drives, modems, sound cards, speakers, and digital cameras.

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Central Processing Unit

• has 2 components to execute program instructions

– Arithmetic/Logic Unit performs arithmetic operations, and makes logical comparisons.

– Control Unit controls the order in which your program instructions are executed.

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Flow of Information

• The parts are connected to one another by a collection of wires called a bus

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The Fetch-Execute Cycle

• Fetch the next instruction

• Decode the instruction

• Get data if needed

• Execute the instruction

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The Fetch-Execute Cycle