Welcome to ComputingWelcome to Computing

Presentation slides modified by M. A. Papalaskari from “Java Software

Solutions Foundations of Program Design (3rd ed.)” by John Lewis and William Loftus

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OverviewOverview

History of computing

Information representation

Computer hardware

Computer software

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History of ComputersHistory of Computers

Mechanization of Mechanization of arithmeticarithmeticAbacus (China 2400 bc) Stonehenge (1900-1600 bc) Napier's bones (c. 1600, a precursor of the slide rule) Pascal's adder (1642) Leibniz's calculator (1670s) Babbage's Difference engine (1800’s)modern calculators

Automatic control of Automatic control of computationcomputationJacquard loom (1801) Babbage's Analytical engine (1822)Holerith's census machine (1890)

Modern ComputerModern ComputerStored program and the fetch/decode/execute cycle (John von Neumann, 1945) ENIAC - first fully electronic digital computer (Eckert and Mauchley, 1946)

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Hardware and SoftwareHardware and Software

Hardware• the physical, tangible parts of a computer• keyboard, monitor, disks, wires, chips, etc.

Software• programs and data• a program is a series of instructions

A computer requires both hardware and software

Each is essentially useless without the other

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CPU and Main MemoryCPU and Main Memory

CentralProcessing

Unit

MainMemory

Chip that executes program commands

Intel Pentium 4 orSun ultraSPARC III Processor

Primary storage area for

programs and data that are in

active use

Synonymous with RAM

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Secondary Memory DevicesSecondary Memory Devices

Floppy Disk

Hard DiskMain

Memory

CentralProcessing

Unit

Secondary memorydevices providelong-term storage

Information is movedbetween main memoryand secondary memoryas needed

Hard disksFloppy disksZIP disksWritable CDsTapes

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Input / Output DevicesInput / Output Devices

Monitor

Keyboard

MainMemory

CentralProcessing

Unit

Floppy Disk

Hard Disk

I/O devices facilitate userinteraction

Monitor screenKeyboardMouseJoystickBar code scannerTouch screen

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Analog vs. DigitalAnalog vs. Digital

There are two basic ways to store and manage data:

Analog• continuous, in direct proportion to the data

represented• music on a record album - a needle rides on ridges in

the grooves that are directly proportional to the voltages sent to the speaker

Digital• the information is broken down into pieces, and each

piece is represented separately• music on a compact disc - the disc stores numbers

representing specific voltage levels sampled at specific times

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Digital InformationDigital Information

Computers store all information digitally:• numbers• text• graphics and images• video• audio• program instructions

In some way, all information is digitized - broken down into pieces and represented as numbers

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Representing Text DigitallyRepresenting Text Digitally

For example, every character is stored as a number, including spaces, digits, and punctuation

Corresponding upper and lower case letters are separate characters

H i , H e a t h e r .

72 105 44 32 72 101 97 116 104 101 114 46

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Representing imagesRepresenting images

A digitized image consists of pixels (picture elements)

Black and white images can be stored using one bit per pixel (1 = white and 0 = black)

There are several techniques for representing colors

Often a color is represented as a mixture of the three additive primary colors: Red, Green, and Blue

In many applications each color is represented by three numbers between 0 and 255 that collectively are called an RGB value

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The Central Processing UnitThe Central Processing Unit

A CPU is on a chip called a microprocessor

It continuously follows the fetch-decode-execute cycle:

fetch

Retrieve an instruction from main memory

decode

Determine what theinstruction is

execute

Carry out theinstruction

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The Central Processing UnitThe Central Processing Unit

The CPU contains:

Arithmetic / Logic Unit

Registers

Control Unit

Small storage areas

Performs calculations and makes decisions

Coordinates processing steps

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The Central Processing UnitThe Central Processing Unit

The speed of a CPU is controlled by the system clock

The system clock generates an electronic pulse at regular intervals

The pulses coordinate the activities of the CPU

The speed is measured in megahertz (MHz)

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Software CategoriesSoftware Categories

Operating System• controls all machine activities• provides the user interface to the computer• manages resources such as the CPU and memory• Windows XP, Windows 2000, Unix, Linux, Mac OS

Application program• generic term for any other kind of software• word processors, missile control systems, games

Most operating systems and application programs have a graphical user interface (GUI)