1. SOFTWARE DEVELOPMENT METHOD
CHAPTER 2
SOFTWARE DEVELOPMENT METHOD

2. Objectives In this chapter you will learn:
The electronic computers and its’ suitable programming language
To solve problem using problem-solving strategies and methods
The algorithm as a guidance in designing program

3. Subtopics Electronic Computers Introduction to Programming
Software Development Method (SDM)
Algorithm Design

4. Electronic Computers What is computer ?
A computer is an electronic device designed to perform operations specified with a set of instructions called a program.
A computer include both hardware & software

5. Why we need computers ? The use of Computer in daily activities
bill payment, booking transportation ticket, communication services, ing friends, on-line communication, subject registration, course assessments & etc.
As for engineering students, you should develop the ability to solve problems, and it is very likely that you will need to use computers for problem solving

6. Computer Hardware (1) Major hardware components :
Central Processing Unit (CPU)
Control unit (CU) & Arithmetic/Logic Unit (ALU)
Memory (main memory)
Storage Devices (disks, CDs, tapes)
Input/Output Devices (monitors, keyboards, mice, printers
Communication Devices (modems and network interface cards (NIC cards)
Note : The components are connected through a subsystem called a
bus that transfers data between the components.
(Source : Y.D. Liang “Introduction to Programming with C++”, Comprehensive
Version. International Edition. Pearson Education, 2007)
BEC SEM /2011

7. Computer Hardware (2) BEC 10102 SEM 1 2010/2011
HARDWARE = PERIPHERAL EQUIPMENT CENTRAL/SYSTEM UNIT
BEC SEM /2011

8. Computer Software Operating System (OS) Unix, Window, Linux
Software Tools (Utility Packages)
word processors (MicrosoftWord, WordPerfect)
spreadsheet programs (Excel, Lotus1-2-3, ...)
Computer Languages/ Programming Languages
machine language
assembly language
binary language
high level languages (C, C++, Ada, Fortran, Basic, java)
User Developed Programs
SMAP On-Line
MayBank2you

9. Intro to Programming
Programming is the core of everything to do with computers, computing, networked systems, management information systems, multimedia and so on (all computer-based things)
Everything that runs on a computer is a program and somebody (programmer) has to write it using specific programming language. To understand how computers can be used, how applications work, how systems are configured, it is necessary for you to understand what programs are and how they are constructed.
BEC SEM /2011

10. Software Development Method (SDM)
What is Problem ?
The process of transforming the description of a problem into the solution of that problem by using our knowledge of the problem domain and by relying on our ability to select and use appropriate problem-solving strategies, techniques, and tools.

11. SDM Phases provides us with a precise definition of the problem.
we identify problem inputs, outputs, constraints, and formulas and equations to be used.
concerned with developing an algorithm (subtopic 1.4) for the solution of the problem.

12. SDM : Coding & Implementation
Code the finalized algorithm using a suitable programming language.
Go through the compiling & execution process.
Normally, you will face this three types of programming errors
Logic/Design errors
Syntax errors
Runtime errors

13. Logic/Design errors
Design errors occur during the analysis, design, and implementation phases.
We may choose an incorrect method of solution for the problem to be solved, we may make mistakes in translating an algorithm into a program, or we may design erroneous data for the program.
Design errors are usually difficult to detect.
Debugging them requires careful review of problem analysis, algorithm design, translation, and test data.

14. Syntax Errors
Syntax errors are violations of syntax rules, which define how the elements of a programming language must be written.
They occur during the implementation phase and are detected by the compiler during the compilation process. In fact, another name for syntax errors is compilation errors.
If your program contains violations of syntax rules, the compiler issues diagnostic messages.
Depending on how serious the violation is, the diagnostic message may be a warning message or an error message.

15. Runtime Errors
Run-time errors are detected by the computer while your program is being executed.
They are caused by program instructions that require the computer to do something illegal, such as attempting to store inappropriate data or divide a number by zero.
When a run-time error is encountered, the computer produces an error diagnostic message and terminates the program execution.
You can use diagnostic messages to debug run-time errors.

16. SDM : Testing and Verification
Testing the completed program to verify that it works as desired.
Do not rely on just one test case .
Run the program several times using different sets of data to make sure that it works correctly for every situation provided in the algorithm.
BEC SEM /2011

17. SDM : Documentation & Maintenance
For every problem solving, there are 5 things to be
documented :
Program description
Algorithm development and changes
Well-commented program listing
Sample test run
User’s manual
Maintenance is concerned with ongoing correction of problems, revision to meet changing needs and addition of new features. The better the documentation is, the efficiently this phase can be performed.

18. Algorithm Design An algorithm is a sequence of a finite
number of steps arranged in a specific
logical order that, when executed,
produces the solution for a problem.
An algorithm design should be put on
paper. For this purpose, and also to
facilitate its development, we resort to
pseudocoding and flowcharting

19. Analogy A) How to use ATM Machine ? i. Step 1 ? ii. Step 2 ? ……….
x. Final step ?
B) How to register courses using SMAP
on-line ?

20. Pseudocoding Short English phrases with a limited
vocabulary are use to describe the
algorithm (the processing steps). A
pseudocode must :
have a limited vocabulary
be easy to learn
produce simple, English-like narrative notation
be capable of describing all algorithms, regardless of their complexity

21. Example of Pseudocode Problem 1 : (Sequence structure)
Compute total of resistor values.
Begin
read resistor1, resistor2
total = resistor1 + resistor2
print “ total “
End

22. Flowcharting
A graphical technique for algorithm design and representation, is equivalent to pseudocoding and can be used as an alternative to it.

23. Flowchart Symbols (1) Symbol Name Of Symbol Description And Example
Terminal
Indicates the beginning or end of an algorithm
Input/Output
Indicates an Input or Output operation
Process
Indicates computation or data manipulation
Decision
Indicates a decision point in the algorithm

24. Flowchart Symbols (2) Symbol Name Of Symbol Description And Example
Loop
Specific for for statement
Indicates the initial, final
and increment values of a loop.
Flow Lines/ Arrow
Used to connect the symbols and indicates the logic flow
On-Page Connector
Provides continuation of a logical path on another point in the same page.
Off-Page Connector
Provides continuation of a logical path on another page

25. Example of Flowchart Problem 1 : (Sequence statements)
Compute total of resistor
values.

26. Pseudocode & Flowchart Convention
Sequence Structure
a series of steps or statements that are executed in order (ex : as shown in Problem 1)
Selection Structure
Define two courses of action depending on the outcome condition ( true or false)
Repetition control structures
Specifies a block of one or more statements that are repeatedly executed until a condition is satisfied.

27. Sequence Structure
begin
Statement_1
Statement_2 …
Statement_n
end

28. Selection Structure if condition statement Double Selection (if-else)
Single Selection (if)
if condition
statement
Double Selection (if-else)
if condition
then_part
else
else_part
end_if
BEC SEM /2011

29. Repetition Structure while condition loop-body end_while
BEC SEM /2011

30. Applying the SDM ( Phase 1 to 3)
Problem :
The C programming test scores can be classified into two condition, PASS and FAIL. The student is require to input their marks in positive integer . If the score is greater than or equal 50 message Pass will appear, message Fail otherwise

31. Applying the SDM : Phase 1 & 2
Phase 1 : Requirement Specification
Selection Structure
test scores, message ‘PASS’, message ‘FAIL’, greater or equal to 50, less than 50
Phase 2 :
Data requirements :
Input : test_score
Output : ‘PASS’ or ‘FAIL’
Relevant formula : None
Constrain : the test score must greater than 0
(zero)
Condition : test_score >= 50
test_score < 50

32. Applying the SDM : Phase 3 (1)
Phase 3 : Design ( Pseudocode/Flowchart)
Pseudocode
Begin
Read the test scores
Begin while
while test_score < 0
Print ‘ Re-enter your score and must greater than 0’
Read the test_score
End while
if test_score >= 50
print ‘PASS’
else
print ‘FAIL’
End
BEC SEM /2011

33. Applying the SDM : Phase 3 (2)
Flowchart
BEC SEM /2011

34. Exercises
Write an algorithm (Pseudo code and flow chart) for attending a lecture
Write an algorithm that calculate the multiplication of two integer numbers.
Write an algorithm which can determine the positive and negative integer.
Write an algorithm that can print series of odd numbers between 0 and 12.

35. Start
Wake Up
Take Shower
Get Dressed
Eat Breakfast
Has Transport
Walk to Lecture hall N Y
Late?
Go back home Y
Take Transport N
End
Enter Class

36. Begin
Wake up
Take shower
Get dressed
Eat breakfast
If has transport
take transport
Else
walk to lecture hall
If late
go back home
enter class
end

37. Begin int w; int l; int area; w=20; l=25; area=w
Begin int w; int l; int area; w=20; l=25; area=w*l print “Your area is “ print area end

38. Write a program to calculate the square area. Print area
Design a Program that a salesperson gets 6 percent commission on sales less than $1000, 8 percent on sales in the range $1000 through $2000, and 10 percent on sales in excess of $2000. Print the commission.

39. Write a program that can read age
Write a program that can read age. Print “young” if the age less than 20, print “Adult” if the age between 20 to 30 and print “old” if the age above 30.