Charles Babbage (1791-1871 ) • Creator of the Analytical Engine - the first general-purpose digital computer (1833) The Analytical Engine • A programmable, mechanical, digital machine • Could carryout any calculation • Could mae decisions based upon the results of the p re!ious calculation • Components" input# memory# processor# output Ada, Countess of Lovelace(1815-52) • $abbage" the father of computing • Ada" the mother % • &rote a program for computing the $ernoulli's seuence on the Analyti cal Engine - orld's 1st computer program • Ada" A programmi ng language specifically designed by the *+ ept of efense for de!eloping military applications as named Ada to honor her contributions toards computing A lesson that e all can learn fro! Babbage"s L#fe • Charles $abbage had huge difficulties raising money to fund his research • As a last resort, he designed a cle! er mathematical scheme along ith Ada, t he Countess of o!elace • .t as designed to increase their od ds hile gambling/ They bet money on horse races to raise enough money to support their research e0periments • uess hat happened at the end% The lost e!ery penny that they had/ 1. 2ast2. $ored3. +torageHere is a fact: .n 14 eep $lue, a supercomputer designed by .$5, beat ary 6asparo!, the &orld Chess Champion That computer as e0cepti onally fast, did not get tired or bor ed/ .t 7ust ept on anal$%#ng the situation and ept on search#nguntil it found the perfect mo! e from its list of possibl e mo!es
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• Creator of the Analytical Engine - the first general-purpose digital computer (1833)
The Analytical Engine
• A programmable, mechanical, digital machine
• Could carryout any calculation
• Could mae decisions based upon the results of the pre!ious calculation
• Components" input# memory# processor# output
Ada, Countess of Lovelace(1815-52)
• $abbage" the father of computing
•
Ada" the mother%
• &rote a program for computing the $ernoulli's seuence on the Analytical Engine -
orld's 1st computer program
• Ada" A programming language specifically designed by the *+ ept of efense forde!eloping military applications as named Ada to honor her contributions toardscomputing
A lesson that e all can learn fro! Babbage"s L#fe
• Charles $abbage had huge difficulties raising money to fund his research
• As a last resort, he designed a cle!er mathematical scheme along ith Ada, theCountess of o!elace
• .t as designed to increase their odds hile gambling/ They bet money on horseraces to raise enough money to support their research e0periments
• uess hat happened at the end% The lost e!ery penny that they had/
1. 2ast 2. $ored 3. +torage
Here is a fact:
.n 14 eep $lue, a supercomputer designed by .$5, beat ary 6asparo!, the &orld ChessChampionThat computer as e0ceptionally fast, did not get tired or bored/ .t 7ust ept on anal$%#ng thesituation and ept on search#ng until it found the perfect mo!e from its list of possible mo!es
A test proposed to determine if a computer has the ability to thin/ .n 1;<, Alan Turing (Turing,1;<) proposed a method for determining if machines can thin/ This method is non as TheTuring Test/
=acuum Tube > 1<?
A !acuum tube is 7ust that" a glass tube surrounding a !acuum (an area from hich all gases hasbeen remo!ed)/ A $ritish scientist named @ohn A/ 2leming made a !acuum tube non today asa diode/ Then the diode as non as a !al!e,
A$C > 13The Atanasoff-$erry Computer as the orldBs first electronic digital computer/ .t as built by@ohn =incent Atanasoff and Clifford $erry at .oa +tate *ni!ersity during 134-?/
Dar!ard 5ar 1 > 1?3Doard Aien and race Dopper designed the 5A6 series of computers at Dar!ard *ni!ersity/clicing metal parts, ;; feet long and 8 feet high/ The ;-ton de!ice contained almost 4F<,<<<separate pieces/ *sed by the *+ Ga!y for gunnery and ballistic calculations, the 5ar . as inoperation until 1;/
EG.AC > 1?F
EG.AC (&lectrical 'umerical ntegrator And Calculator)/ The */+/ military sponsored their research.t too the team about one year to design the EG.AC and 18 months and ;<<,<<< ta0dollars to build it/ The EG.AC contained 14,?F8 !acuum tubes, along ith 4<,<<< resistors and
1<,<<< capacitors/rans#stor The first transistor as in!ented at $ell aboratories on ecember 1F, 1?4 by &illiam +hocley/Compared to !acuum tubes, it offered"
*lo++$ #s . 195/0 .n!ented at the .mperial *ni!ersity in Toyo by Ioshiro Gaamats/
*G.=AC 1 > 1;1
The first commercially successful electronic computer, *G.=AC ., as also thefirst general purpose computer - designed to handle both numeric and te0tualinformation/ .t as designed by @/ Jresper Ecert and @ohn 5auchly/
Compiler > 1;race 5urray Dopper an employee of emington-and ored on the G*.=AC/ +he
too up the concept of reusable softare in her 1; paper entitled The Education of a
Computer and de!eloped the first softare that could translate symbols of higher computer languages into machine language/ (Compiler)
AA'& . 1939 AJA as assigned to research ho to utiliHe their in!estment in computers !ia
Command and Control esearch (CC)/ r/ @/C// iclider as chosen to head this effort/
e!eloped for the *+ o Ad!anced esearch Jro7ects Agency
.ntel ?<<? > 141
The ?<<? as the orldBs first uni!ersal microprocessor/
Altair 88<< > 14;
e!elopers Edard oberts, &illiam Iates and @im $ybee spent 143-14? to de!elop the 5.T+
(5icro .nstruments Telemetry +ystems ) Altair 88<</ The price as K34;, contained ;F bytes of memory (not ;F),but had no eyboard, no display, and no au0iliary storage de!ice/
Cray 1 > 14F
The Cray 1 as the orldBs first supercomputer, a machine that leapfrogged e0isting technologyhen it as introduced in 141/
.$5 JC > 181
Ln August 1, 181, .$5 released their ne computer, re-named the .$5 JC/ The JC stood for personal computer maing .$5 responsible for populariHing the term JC/
The first .$5 JC ran on a ?/44 5DH .ntel 8<88 microprocessor/ The price tag started at K1,;F;,hich ould be nearly K?,<<< today/
Apple 5acintosh > 18?
Apple introduced the 5acintosh to the nation on @anuary , 18?/ The original5acintosh had 18 ilobytes of A5, although this first model as simply called5acintosh until the ;16 model came out in +eptember 18?/ The 5acintoshretailed for K?;/
&orld &ide &eb -18&&& uicly gained great popularity among .nternet users/
4hat #s 4orld 4#de 4eb
• A huge resource of information
• ogically unified" Any one from any here can access the information using a !erysimple scheme consisting of lins M *s
• Jhysically distributed" The information is stored on .nternet-connected computers thatare spread all o!er the globe
Broser A broser is an application program that pro!ides a ay to loo at and interact ith allthe information on the &orld &ide &eb/
6L
* (*niform esource ocator, pre!iously *ni!ersal esource ocator) > pronouncedI*-AD-ED or, in some uarters, *D - is the address of a file (resource) accessibleon the .nternet/
o !an$ 4eb +ages are there• .n 1 there ere 8<< million &eb pages (1; terra (1<1) bytes of te0t) • .n year <<, the number is supposed to be 8 billion
• .f you spend a minute re!ieing each of these pages, it ill tae more than 1;,<<< yearsto go through them all
4hat #s secret beh#nd the e+los#ve groth of the 4eb
• Anarchy > any page is alloed to lin to any other • There are no controls o!er ho puts hat on the &eb
E!eryone can put hate!er they ant to put on the &eb > and they doN
he !ost +o+ular 4eb s#tes
• AL > 5ost popular .+J's &eb site
• 5icrosoft > 5ost popular softare de!eloper's &eb site
• Iahoo > 5ost popular multi-ser!ice &eb site
• AmaHon > most popular shop on the &eb
• CGG > most popular nes &eb site
• oogle > most useful search engine
4hat #s a 4eb #te
A &eb site is a related collection of &orld &ide &eb (&&&) files that includes a beginning filecalled a home page/
4hat #s a 4eb earch &ng#ne
• +earch engines continuously scan the &eb and compile a list of all the &eb pages thatthey find
• Joered by 81 microprocessors • F T$ of memory# 1F< T$ of storage capacity
;a#nfra!e Co!+uters
• Also called 9Enterprise +er!ers: • esigned for performing multiple, intensi!e tass for multiple users simultaneously • *sed by large businesses (e/g/ bans, e-commerce sites), military, and industrial
organiHations • esigned for !ery-high reliability • Cost in millions of dollars
ervers<;#n#co!+uters
• The name minicomputers used to define the class of computers that lies beteenpersonal computers and mainframes
•
enerally are more reliable than destops, but not as solid as the mainframes • Costs in hundreds of thousands of dollars
esto+ Co!+uters• Also called microcomputers
• o-end destops are called JC's and high-end ones 9&orstations:
• JC's are used for running producti!ity applications, &eb surfing, messaging
• &orstations cost a fe thousand dollars# JC around a K1<<<
;ob#le Co!+uters
La+to+s, +al!to+s, and earable computers are !ery capable computers but are light-eight
and consume !ery little poer
La+to+s
• also called noteboo computers • generally eigh around g • use special lo-poer processors • typically ha!e ;F5$ memory, • ?<$ of storage • can or for more than hours on battery/ • Their usage is similar to that of JCs
They cost in the range of K1;<<-;<< al!to+s,
• also non as JA's - Jersonal igital Assistants&eigh less than a pound
• ha!e !ery lo-poer processors • 6$'s of memory • 5$'s of storage capacity • Can run for many hours on AA batteries • *sed as an electronic !ersion of a pocet diary • Also for &eb surfing and e-mail or e!en as mobile phones
• are small in siHe • carried in a pocet • orn on the arm, aist •
or head or elsehere on the body • Capability similar to JA's • but more e0pensi!e • They are alays LG, and alays accessible/ That is, the user can alays enter and
e0ecute commands, e!en hile aling around or doing other acti!ities • Each soldier of the future ill be fitted ith one
an#ng =r=t= #nstalled nu!ber
• JC's • JA's •
&orstations • +er!ers • &earables (ill tae the top spot in future) • 5ainframes • +upercomputers
&ssent#al ardare Co!+onents At the highest le!el, to things are reuired for computing
ardare0 The physical euipment in a computing en!ironment such as the computer and itsperipheral de!ices (printers, speaers, etc/)
oftare0 The set of instructions that operates !arious parts of the hardare/ Also termed as
9computer program
All co!+uters have the follo#ng essent#al hardare co!+onents0
n+utThe de!ices used to gi!e the computer data or commands are called .nput de!ices/ .ncludeseyboard, mouse, scanner, etcrocessor
A processor is the logic circuitry that responds to and processes the basic instructions that dri!e acomputer/;e!or$5emory is the electronic holding place for instructions and data that your computerBsmicroprocessor can reach uicly/
torageComputer storage is the holding of data in an electromagnetic form for access by a computer processor/>ut+utThe de!ices to hich the computer rites data are called Lutput de!ices
A mouse is a small de!ice that a computer user pushes across a des surface in order to point toa place on a display screen and to select one or more actions to tae from that position/?e$boardLn most computers, a eyboard is the primary te0t input de!ice/ A eyboard on a computer isalmost identical to a eyboard on a typeriter/ @o$st#c.n computers, a 7oystic is a cursor control de!ice used in computer games/ #g#tal Ca!era
A digital camera records and stores photographic images in digital form that can be fed to acomputer as the impressions are recorded or stored in the camera for later loading into acomputer or printer/ Currently, 6oda, Canon, and se!eral other companies mae digitalcameras/
;#cro+hone A de!ice that con!erts sound a!es into audio signals/ These could be used for sound recordingas ell as !oice chatting through internet/canner
A scanner is a device that captures images from photographic prints, posters, magazine
pages, and similar sources for computer editing and display.
What is a Port?
Ln computer and telecommunication de!ices, a port (noun) is generally a specific place for being
physically connected to some other de!ice, usually ith a socet and plug of some ind/;an$ $+es of orts
1. Jarallel 2. +erial 3. +C+. 4. *+$
5.2ireire
arallel An interface on a computer that supports transmission of multiple bits at the same time# almoste0clusi!ely used for connecting a printer/er#al.t is a general-purpose personal computer communications port in hich 1 bit of information istransferred at a time/C
A port thatBs faster than the serial and parallel ports but sloer and harder to configure than theneer *+$ port/ Also no as the +mall Computer +ystem .nterface/6B*+$ (*ni!ersal +erial $us) is a plug-and-play hardare interface for peripherals such as theeyboard, mouse, 7oystic, scanner, printer and modem/*#re#re2ire&ire is simply a really fast port that lets you connect computer peripherals and consumer electronics to your computer ithout the need to restart/
A;A5 (random access memory) is the place in a computer here the operating system,unch cards
A card on hich data can be recorded in the form of punched holes
>;L5 is built-in computer memory containing data that normally can only be read, not ritten to/ard d#sDard dis is a computer storage de!ice hich sa!es and retrie!es the data hen reuired/*lo++$ d#s
A disette is a random access, remo!able data storage medium that can be used ith personalcomputers/a+e.n computers, tape is an e0ternal storage medium, usually both readable and ritable, can storedata in the form of electromagnetic charges that can be read and also erased/C
A compact disc Psometimes spelled disk Q (C) is a small, portable, round medium forelectronically recording, storing, and playing bac audio, !ideo, te0t, and other information indigital form/= (digital !ersatile disc) is an optical disc technology that is e0pected to rapidly replace theC-L5 disc (as ell as the audio compact disc) o!er the ne0t fe years/ The digital !ersatiledisc (=) holds ?/4 gigabyte of information on one of its to sides, or enough for a 133-minutemo!ie/
RA DE2mailto"altafV!u/edu/pSaltafV!u/edu/pROASR$SROJS
RJS. teach the RA DE2http"OO/!u/edu/pOcs1<1OS.ntroduction to ComputingROAS course/ROJSRO$LISRODT5S
;#cro+rocessor A microprocessor (abbre!iated as or u) is a computer processor on a microchip/ .tBssometimes called a logic chip/ A microprocessor is designed to perform arithmetic and logicoperations that mae use of small number-holding areas called registers/
ntegrated c#rcu#t• Commonly non as an .C or a chip • A tiny piece of +ilicon that has se!eral electronic parts on it
A ;#cro+rocessor $ste!• 5icroprocessors are poerful pieces of hardare, but not much useful on their on • A microcomputer is 1 e0ample of a microprocessor system
;#cro Controller • 5icro-controllers are another type of microprocessor systems • They are generally not that poerful, cost a fe dollars a piece, and are found embedded
in !ideo games, =Cs, microa!e o!ens, printers, autos, etc/
he ;a#n ;e!or$ Bottlenec
• 5odern super-fast microprocessors can process a huge amount of data in a shortduration
• They reuire uic access to data to ma0imiHe their performance
That small amount of memory located on the same chip as the microprocessor is called Ln-Chip Cache 5emory
Bus nterface 6n#tThe bus interface unit is the part of the processor that interfaces ith the rest of the JC/
nstruct#on ecoder The instruction decoder of a processor is a combinatorial circuit sometimes in the form of a read-only memory, A decoder is a de!ice hich is the re!erse, undoing the encoding so that the original informationcan be retrie!ed/
;#cro+rocessor Bu#ld#ng Blocs
Ar#th!et#c : Log#c 6n#t (AL6) An arithmetic and logical unit (AL6) also non as nteger 6n#tD is one of the core componentsof all central processing units/
*loat#ng-o#nt 6n#t (*6) A floating point unit (2J*) is a part of a CJ* specially designed to carry out operations on floatingpoint numbers/
eg#sters A register is a de!ice for storing data/ .t is a small amount of !ery fast computer memory used tospeed the e0ecution of computer programs by pro!iding uic access to commonly used !alues/ata reg#sters are used to store integer numbers/Address reg#sters hold memory addresses and are used to access memory/Eeneral ur+ose reg#sters can store both data and addresses/*loat#ng o#nt reg#sters are used to store floating point numbers/Constant reg#sters hold read-only !alues (e/g Hero or one)/ector reg#sters hold data for +ingle .nstruction 5ultiple ata (+.5) instructions/+ec#al ur+ose reg#sters hich store internal CJ* data lie the stac pointer or processorstatus ords/
Control 6n#t A control unit is the part of a CJ* or other de!ice that directs its operation/ The outputs of the unitcontrol the acti!ity of the rest of the de!ice/ A control unit can be thought of as a finite statemachine/ .t is called the brain of computer microprcessor/
nstruct#on etThe set of machine instructions that a microprocessor recogniHes and can e0ecute > the onlylanguage microprocessor nos
• ;; million transistors • 3-bit ord siHe • A*'s, each oring at ?/?DH • 18-bit 2J* • </13 micron process • Targeted use" JC's and lo-end orstations
• Cost" around KF<<
;oore"s La• .n 1F;, one of the founders of .ntel > ordon 5oore > predicted that the number of
transistor on an .C (and therefore the capability of microprocessors) ill double e!ery
year/ ater he modified it to 18-months
&nhanc#ng the ca+ab#l#t$ of a !#cro+rocessor
The computing capability of a microprocessor can be enhanced in many different ays"
• $y increasing the cloc freuency • $y increasing the ord-idth • .mpro!ing the architecture
B#nar$
($ase ) number systemec#!al
($ase 1<) number system B#nar$ (Base 2) number system consists of 7ust to digits <,1ec#!al (Base 1/) number system consists of ten symbols or digits <,1,,3,?,;,F,4,8,
• &hen the user needs something done by the computer, heOshe gi!es instructions in theform of +& to computer D&
;ach#ne Language
• 5achine language, though readily understood by microprocessors, is !ery difficult to ritein for human programmers
Language ranslators
• Duman programmers rite programs in a language that is easy to understand for them
oftare evelo+!ent• The +& de!elopment process in!ol!es many steps, and coding, that is typing the
instructions in a high-le!el language is only a small part of that process > taing-up onlyaround 1;Y of the effort
o ;aPor $+es of oftare
• $ste! 4Jrograms that generally perform the bacground tass in a computer/ These programs,many times, tal directly to the D&
• A++l#cat#on 4Jrograms that generally interact ith the user to perform or that is useful to the user/These programs generally tal to the D& through the assistance of system +&
$ste! oftare
>+erat#ng $ste!s
• .t interacts directly ith the computer D& • Lther +& normally does not directly interact ith the D&, but through the L+
1- Compiler translates the program ritten in a D in one go/- nterpreter translates the D program one statement at time/
ev#ce r#vers• A computer program that facilitates the communication beteen the computer and a
peripheral de!ice (e/g/ printer, mouse, etc/)
A++l#cat#on oftare Application +& are programs that interact directly ith the user for the performance of a certaintype of or
• c#ent#f#c<eng#neer#ng<gra+h#cs 45athematica# AutoCad# Corel ra
• Bus#ness 4The billing system for the mobile phone company
• roduct#v#t$ 4&ord processors# +preadsheets
• &nterta#n!ent 4ames
• &ducat#onal 4Electronic encyclopedias# The =* &eb site
Another a$ of class#f$#ng oftare
• +hrin-&rapped +& -Iou can 7ust go to a shop and buy it
• Custom-built +& -Iou cannot 7ust go to a shop and buy it# you ha!e to find someone ho can de!elop itfor you
4ho >ns oftare• enerally, although a piece of +& that is being used by millions, it is not oned by any of
themN .nstead, it is oned by the maer of the +&
hree ;a#n $+es of oftare L#censes
1. ro+r#etar$ > 5ost softare on a &indos JC or a 5acintosh belongs to this category 2. *reeare > 5ost softare on a inu0 JC belongs to that category 3. hareare > the category hich lies beteen the abo!e to categories
ro+r#etar$ 4 L#cense
•
The user needs to pay the maer of the +& for buying a license that allos the user touse the +&
nteract#ve-!odeThe user runs the program on the computer and eeps on interacting ith the computerhile the program runs
E0ample" &ord processor
Batch-!odeThe user starts the program and the computer processes the pro!ided data and producesresults ithout any further inter!ention of from the user
Electronic replacement for ledgers .s used for automating engineering, scientific, but in ma7ority of cases, business calculationsm/
+preadsheet +& ()
Consist of cells arranged in ros and columns
Jresentation e!elopment +&
*sed to prepare multimedia material for lectures M presentations to display ey points, graphics,animation, or !ideo ith the help of multimedia pro7ectors
+mall-+cale atabases +& (1)
$asy to use applications designed for efficient storage and fast and easy retrieval of data
%mall&%cale 'atabases %( )2*$efore the ad!ent of the currently popular 9relational: database model, the data basing functionas performed using hat is called the 9flat-f#le: model
A database consists of a file or a set of files/ .nformation in these is stored in the form of records,and the records are further subdi!ided into fields
Jroducti!ity +& +uites
A set of stand-alone producti!ity applications designed to or easily ith each other E0amples" 5+ Lffice, Corel &ordJerfect Lffice
ocument-Centered Computing (CC)
The increasing cooperation among the apps included in producti!ity suites has gi!en rise to ane computing model called CC
A JC can be made the hub of a music maing studio ith help of appropriate D& M +&.ne0pensi!e, easy-to-use !ideo editing +& has recently become a!ailable for the i5ac
• +mall programs that are a part of the &eb page and run on the user's (client's) computer •
They interact ith the user to collect info or to accomplish other tass • Lnce it has been collected, they may help pass the collected info on to a ser!er-sidescript
Advantages of Cl#ent-#de cr#+t#ng• educed ser!er load as it does not ha!e to send messages to the user's broser about
missing or incorrect data #sadvantages
• Client-side scripts do not or ith all brosers • +ome user intentionally turn scripting off on their brosers
@avacr#+t
4h$ @avacr#+t@a!a+cript can be used (along ith DT5) to de!elop interacti!e content for the &eb
4hat #s @avacr#+t
• A programming language specifically designed to or ith &eb brosers • .t is designed to be used for de!eloping small programs > called scripts >
efinition of Algorithm
+euence of steps that can be taen to sol!e a gi!en problem is called Algorithm/
E0amples"
AdditionCon!ersion from decimal to binaryThe process of boiling an eggThe process of mailing a letter +orting+earching
Lrigin of the Term 9Algorithm:The name deri!es from the title of a atin boo" Algoritmi de numero .ndorum
That boo as a translation of an Arabic boo" Al-6hariHmi Concerning the Dindu Art ofeconingThat boo as ritten by the famous -th century 5uslim mathematician, 5uhammad ibn 5usaal-6hariHmi
Al-6harHmi
Al-6hariHmi li!ed in $aghdad, here he ored at the ar al-Dimaar al-Dima acuired and translated boos on science and philosophy, particularly those inree, as ell as publishing original researchThe ord Algebra has its origins in the title of another atin boo hich as a translation of yetanother boo ritten by Al-6harHmi" 6itab al-5uhtasar fi Disab al-@abr aBl-5uabala
reedy Algorithm
An algorithm that alays taes the best immediate, or local solution hile finding an anser
reedy algorithms may find the o!erall or globally optimal solution for some optimiHationproblems
eterministic Algorithm
An algorithm hose beha!ior can be completely predicted from the inputsThat is, each time a certain set of input is presented, the algorithm gi!es the same results as anyother time the set of input is presented/
andomiHed Algorithm
Any algorithm hose beha!ior is not only determined by the input, but also !alues produced by arandom number generator
Deuristic
A procedure that usually, but not alays, ors or that gi!es nearly the right anser
The $rute 2orce +trategy
A strategy in hich all possible combinations are e0amined and the best among them is selected
A graphical representation of a process (e/g/ an algorithm), in hich graphicob7ects are used to indicate the steps M decisions that are taen as the processmo!es along from start to finish
An algo. is +correct if its-
> %emantics are correct
>
%ynta is correct
%emantics-/he concept
embedded in an algorithm )the
soul0*
%ynta-/he actual
representation of an algorithm
)the body0*
WA!"!#$%
&' An algo. can besyntactically correct, yetsemantically incorrect
very dangerous situation0
(' %yntactic correctness iseasier to chec as compared
epeat the folloing steps hile the list is un-sorted"+tart ith the first ob7ect in the list+ap it ith the one ne0t to it if they are in the rong order epeat the same ith the ne0t to the first ob7ect6eep on repeating until you reach the last ob7ect in the list
M" .s this the only possible algorithm for sorting a list%A0 Certainly notN .n fact this one (called the 9$ubble sort:) is probably the orst (reasonable)algorithm for sorting a list > it is 7ust too slo
o!e of th#ngs that @avacr#+t cannot doQ•
The folloing file ops/ on the client computer" -- ead -- 5odify -- ename -- elete -- Create
• Create graphics (although, it does ha!e the ability to format pages through DT5 -including the placement of graphics)
o!e of the th#ngs that @avacr#+t can doQ
• Control the appearance of the broser • Control the content and appearance of the document displayed in the broser • +tore M modify a limited amount of data about the user in the form of client-side 9cooies:
Cl#ent-#de @avacr#+t Although a !ersion of @a!a+cript e0ists that can be used to rite ser!er-side scripts, our focus inthis course ill only be on client-side scripting
Case ens#t#v#t$• DT5 is not case sensiti!e/ The folloing mean the same to the broser"
RDT5S -- RhtmlSRDtmlS -- Rht5lS
• @a!a+cript is case sensiti!e/ Lnly the first of the folloing ill result in the desiredfunction > the rest ill generate an error or some other undesirable e!ent"on5ouseClic -- Ln5ouseCliconmouseclic -- LG5L*+EC.C6
• E!erything that @a!a+cript manipulates, it treats as an ob7ect > e/g/ a indo or a button
'ot >bPect->r#entedQ
• @a!a+cript is not a true ob7ect-oriented language lie CUU or @a!a • .t is so because it lacs to ey features"
-- A formal inheritance mechanism -- +trong typing
$+es of >bPects• @a!a+cript ob7ects
-- Lb7ects that are part of @a!a+cript -- E0amples" indo, document
• $roser ob7ects -- Lb7ects that contain info not about the contents of the display, but the broser itself -- E0amples" history, na!igator
• *ser-defined ob7ect
$vent 9andlers
• 9E!ents: are actions that occur as a result of user's interaction ith the broser • &e use 9e!ent handlers: Pe/g/ on5ouseL!er(), onClic()Q to design &eb pages that can
react to those e!ents 1/ $atch Jrograms
/ E!ent-ri!en Jrograms
Batch rogra!sThese are typically started from a shell (or automatically !ia a scheduler) and tend to
follo a pattern of".nitialiHe internal dataead input dataJrocess that dataJrint or store results
&vent-r#ven rogra!sE0amples" *.s, microa!e, cameraThe system sends e!ents to the program and the program responds to these as theyarri!e/
Jrogramming anguage
A vocabular$ and set of gra!!at#cal rules for #nstruct#ng a co!+uter to+erfor! s+ec#f#c tass
#gh-level +rogra!!#ng languages, hile simple compared to human languages, are morecomple0 than the languages the uJ actually understands,Asse!bl$ languages are similar to machine languages, but are easier to program in as theyallo a programmer to substitute names for numbers
;ach#ne languages consist of numbers
nter+reters" immediate response, but e0ecute code sloly/Co!+#lers" Taes longer to compile, but super-fast e0ecution/
Jrogramming +& e!elopment
4 es#gn ;ethodolog$ The set of (often fle0ible) rules and guidelines a team of de!elopers follo to construct
.dentifiers are names used by @a!a+cript to refer to !ariables (as ell as ob7ects,properties, methods, and functionsN)/ An identifier must begin ith an alphabeticalcharacter (a-H or A-[) or the underscore 9\: character/