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CHAPTER 1

SOFTWAREDEVELOPMENT

METHOD

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Objectives

In this c ha pter you will lea rn:

The elec tronic c omputers and itssuitab le p rog ramming langua ge

To solve p rob lem using p rob lem-solvingstra teg ies and method s

The a lgorithm as a guidanc e in

designing p rog ram

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Subtop ic s

Elec tronic Com puters

Introd uc tion to Programming

Software Development Method(SDM)

Algorithm Design

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Elec tronic ComputersWhat is c omp uter ?

A computer is an electronic device

designed to perform operations specifiedwith a set of instruc tions c a lled a program.

A computer include both hardware &software

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Why we need c omputers ?

The use of Computer in da ily ac tivities bill payment, booking transportation ticket,communication services, e-mailing friends, on-linecommunication, subject registration, courseassessments & etc .

As for engineering students, you should developthe ability to solve problems, and it is very likelythat you will need to use computers for problemsolving

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Computer Hardware (1)Ma jor hardware components :

Ce ntra l Proc essing Unit (CPU)

Co ntrol unit (CU) & Arithme tic / Log ic Unit (ALU)

Memory (main memory)

Sto rage Devices (disks, CDs, tapes)

Input/Output Devices (monitors, keyboards, mice, printers

Com munic ation Devic es (mode ms and netwo rk interfac ec ards (NIC c ards)

Note : The c om po nents are c onnec ted through a subsystem ca lled a

busthat transfers da ta betwe en the co mpo nents.

(Sourc e :Y.D. Liang Introduction to Programming with C++, Comprehensive

Version. International Edition. Pearson Education, 2007)

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Computer Hardware (2)

HARDWARE = PERIPHERAL EQUIPMENT + CENTRAL/ SYSTEM UNIT

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Computer Softwa reOperating System (OS)

Unix, Window, Linux

Softwa re Too ls (Utility Pac ka ge s)

o word processors (MicrosoftWord, WordPerfect)o spreadsheet programs (Excel, Lotus1-2-3, ...)

Com puter Lang uag es/ Programm ing Lang uageso mac hine language

o assembly languageo binary languag e

o high level lang uag es (C, C++, Ada, Fortran,Basic, java )

User Develop ed Program s

o SMAP On-Lineo MayBank2you

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Intro to Programming

Programming is the core of everything to do withcomputers, computing, networked systems,management information systems, multimedia andso o n (a ll comp uter-based things)

Everything that runs on a computer is a programand someb ody (programmer) has to write it usingspecific programming language. To und ersta ndhow computers can be used, how applicationswo rk, how systems are configured , it is necessary fo r

you to understand what programs are and howthey a re c onstruc ted .

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Software Develop ment Me thod(SDM)

What is Prob lem Solving@Solution ?

The process of transforming the descriptionof a problem into the solution of thatproblem by using our knowledge of theproblem domain and by relying on our

ability to select and use app ropria te problem-solving strategies, techniques, and tools.

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SDM Phases

provides us with a precise definition of theproblem.

we identify problem inputs, outputs, constraints,and formulas and equations to be used.

concerned with developing analgorithm (subtopic 1.4) for the solutionof the problem.

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SDM : Coding & Implementation

Code the finalized a lgo rithm using a suitableprogramming language .

Go through the compiling & executionprocess.

Norma lly, you w ill face this three types ofprog ramm ing errors

Log ic/ Design errors

Syntax errorsRuntime errors

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Logic / Design errors

o Design errors occur during the analysis, design,and implementation phases.

o We m ay c hoose a n inco rrec t me thod of solutionfor the problem to be solved, we may makemistakes in translating an algorithm into aprogram, or we may design erroneous data forthe program .

o Design e rrors a re usua lly difficult to d etec t.

o Debugging them req uires ca reful review of

problem analysis, algorithm design, translation,and test da ta.

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Syntax Errors

o Syntax errors are violations of syntax rules, whichdefine how the elements of a programminglang uag e m ust be w ritten.

o They oc cur during the implementation phaseand are detected by the compiler during thecompilation process. In fact, another name forsyntax errors is com pilation errors.

o If your prog ram c onta ins violations of synta x rules,

the com piler issues diagnostic messages.o Depend ing on ho w serious the violation is, thediag nostic messag e m ay be a wa rning messag eor an error me ssage.

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Runtime Errors

o Run-time e rrors are detec ted by the com puterwhile your prog ram is being exec uted .

o They a re c aused by program instruc tions tha trequire the c om pute r to do som ething illegal,such as attemp ting to store inap propria te d ataor divide a numb er by zero.

o When a run-time error is enc ounte red , thecom puter p rod uces an error d iagnostic messageand terminates the p rog ram exec ution.

o You c an use d iagnostic messag es to d eb ug run-time errors.

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SDM : Testing and Verification

Testing the c omp leted program to verify that itworks as desired .

Do not rely on just one test case .

Run the prog ram several times using differentsets of data to ma ke sure tha t it works correc tly

for every situa tion provided in the a lgorithm.

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SDM : Doc umentation & Maintena nce

For eve ry p rob lem solving, the re a re 5 things to b e

doc umented : Program desc ription

Algorithm developme nt and c hanges

Well-commented program listing

Samp le test run

Users ma nua l

Maintenance is c onc erned with ongo ing c orrec tionof problems, revision to meet changing needs andadd ition of new fea tures. The be tter the doc umentation

is, the e ffic iently this pha se c an be pe rformed .

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Algorithm Design An a lgorithm is a sequence o f a finite

number of steps arranged in a spec ific

log ical order that, when exec uted ,

produces the solution for a p rob lem .

An a lgo rithm design should b e p ut on

paper. For this purpose, and a lso to

fac ilita te its deve lop ment, we resort topseudocoding and flowcharting

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Analogy

A) How to use ATM Mac hine ?i. Step 1 ?ii. Step 2 ?.x. Fina l step ?

B) How to reg iste r c ourses using SMAP

on-line ?

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Pseudocoding

Short Eng lish p hrases with a limited

voc abulary are use to d esc ribe the

a lgorithm (the proc essing steps). A

pseudoc ode must :

have a limited voc abulary

be easy to learn prod uc e simp le, Eng lish-like na rra tive no ta tion

be cap ab le of d esc ribing a ll algo rithms,

reg ard less of their com plexity

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Example of Pseudocode

Prob lem 1 : (Seq uenc e struc ture)

Compute to ta l of resistor va lues.

Begin

rea d resisto r1, resisto r2

total = resistor1 + resistor2

print total

End

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Flowcharting

A graphic a l tec hnique for a lgorithmdesign and rep resenta tion, isequivalent to pseudoc od ing andc an be used as an a lterna tive to it.

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Flowcha rt Symbols (1)

Indicates a decisionpoint in thealgorithm

Decision

Indicatescomputation or datamanipulation

Process

Indicates an Inputor Output operationInput/Output

Indicates thebeginning or end ofan algorithm

Terminal

Description AndExample

Name Of SymbolSymbol

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Flowchart Symbols (2)Description AndExample

Name Of SymbolSymbol

Provides continuation of alogical path on anotherpage

Off-Page Connector

Provides continuation of alogical path on another

point in the same page.

On-Page Connector

Used to connect thesymbols and indicates thelogic flow

Flow Lines/ Arrow

Specific for forstatement

Indicates the initial, final

and increment values of aloop.

Loop

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Example of Flowchart

Problem 1 : (Sequence statements)

Compute total of resistor

values.

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Pseudoc od e & Flow c hart Convention

Sequence Structure

o a series of step s or sta tem ents tha t a reexec uted in order (ex : as shown in Prob lem 1)

Selec tion Structure

o Define two c ourses of ac tion de pending onthe outcom e c ond ition ( true or fa lse)

Repetition c ontrol struc tures

o Spec ifies a b loc k of one or mo re sta tem entsthat a re rep ea ted ly exec uted until a c ond itionis sa tisfied .

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Sequenc e Struc ture

begin

Statement_1

Statement_2

Statement_n

end

Statement_1

Statement_2

Statement_n

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Selec tion Struc ture

Single Selection (if)

if condition

statement

if condition

then_part

else

else_part

end_if

Double Selection (if-else)

condition statement

No

Yes

condition then_part

else_part

no

yes

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Repetition Struc ture

while condition

loop-body

end_while

condition Loop_body

No

Yes

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Ap p lying the SDM ( Pha se 1 to 3)

Problem :

The C programming test sc ores c anbe c lassified into two c ond ition, PASSand FAIL. The student is require toinput the ir ma rks in p ositive integer . Ifthe sc ore is g rea ter than or eq ua l 50message Pass will appear, messageFail otherwise

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Ap p lying the SDM : Phase 1 & 2

Phase 1 : Requirement Spec ification Selec tion Struc ture

test sc ores, me ssage PASS , message FAIL , grea te r orequal to 50, less than 50

Phase 2 :Data req uirem ents :

Input : test_scoreOutp ut : PASS or FAILReleva nt formula : None

Co nstrain : the test score must g rea ter tha n 0(zero)

Cond itio n : test_sc ore >= 50test_score < 50

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Applying the SDM : Phase 3 (1)

Phase 3 : Design ( Pseudocode/Flowchart)

Pseudocode

Begin

Rea d the te st sc ores

Beg in while

while test_score < 0Print Re-ente r your sc ore and m ust greate r than 0

Read the test_score

End whileif test_sc ore >= 50

print PASS

else

print FAILEnd

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Applying the SDM : Phase 3 (2)

Flowchart

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Exercises1. Write an a lgo rithm tha t ca lc ulate

the multiplication of two integernumbers.

2. Write an algo rithm whic h c andetermine the positive andnegative integer.

3. Write an algo rithm tha t can printseries of odd numb ers betw een 0and 12.