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Lecture 2PROBLEM SOLVING

DITP 1113 PROGRAMMING ISEMESTER 1 2014/2015

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System Development

Definition: The critical process determines theoverall quality and success of the program.

If any program is design carefully using good structureddevelopment techniques, the program will be efficient,error-free and easy to maintain.

Most programming projects are built using SystemDevelopment Life Cycle (SDLC).

One of the popular development life cycle is known as thewaterfall model.

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Waterfall model

Identifyprogramcomponents.

Looks atdifferentalternatives

from asystemviewpoint.

Review program specification(input, output, process).

Analyst meet with the users. Read and understand the question.

Algorithm a list of steps to solve theproblem.

Top-down design divide & conquer. Algorithm refinement improvised the

algorithm Flowchart graphically shows the

logic in a solution algorithm. Pseudo code describe a program

using English-like technique.

Write programs(coding).

Compile andexecute.

Updateprogram/systemfrom time totime.

Fix errors &enhance thesystem.

Verify tasks as desired.

Run the programs repeatedly usingdifferent data sets.

Errors type: syntax, run-time or logic

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Development of program

A multi-step process that requires you understand theproblem, develop a solution, write the program, and test it.

To determine how to take the inputs given and thenconvert them into the specified output (program design).

4 steps involve in solving problems:1. Understand the problem2. Develop the solution

3. Write the program

4. Test the program

Example of the problem:

A user can read a map in kilometers but the map showsdistances in miles.

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Development of program (coding)

Problem: Convert distance in miles (m) to kilometers (km).

4 steps involve in solving problems:

1. Understand the given problem

Carefully read the requirements statement.

Ask few clarifying questions even for the simplest problemstatements.

Determines I.P.O. (input, process, output) Input the distances in miles (m)

Process conversion formula

1 mile = 1.609 kilometers

kms = miles x 1.609

Output the distance in kilometers, (km)

1. Understand the problem2. Develop the solution3. Write the program4. Test the program

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Development of program (coding)


4 steps involve in solving problems:

2. Develop the solution Tools to solve problems

Structure chart to design the whole program

Pseudo-code to design the individual parts of a program(eg. module / function)

Flowchart to design the individual parts of a program(eg. module / function)


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4 steps involve in solving problems: 2. Develop the solution

Structure chart

To design the whole program

- The functional flow through

your program.- Shows the breakdown of a

program to its lowestmanageable levels.

- Shows your program dividedinto logical steps each step asseparate module

- The interaction between

modules of your program.

DistanceConversion

Get milesCalculateConversion

Printkilometers


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Pseudo code

To design individual parts of theprogram

(eg. module/function)

- Precise algorithmic description

of program logic- Precisely describe the

algorithm detail, what theprogram being design.

- Requires to define, in sufficientdetail, the steps to accomplishthe task so that can beconverted into a computer

program.

Algorithm Calculate Distance Conversion

received units in miles, msconvert to kilometers using kms = ms * 1.609

return kms in kilometers unit

End Algorithm


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Flowchart

To design individual parts of theprogram

(eg. module/function)

- A graphical or symbolicrepresentation of a process.

- Each step in the process isrepresented by a different

symbol and contains a shortdescription of the processstep.

- Use standardised symbolsand linked together witharrows showing the processflow direction.


Start

kms ms * 1.609

Receive unitsin miles (ms)

End

Return result

(kms)

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4 steps involve in solving problems: 3. Write a program

Remember:

Syntax

; {} () >> > ms; }

void printKilometers()

{ cout

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4 steps involve in solving problems: 4. Test a program two types of testing:-

Blackbox Testing

Whitebox Testing

Differences?

Blackbox Whitebox

Test by the system engineer andthe user.

Test by the programmer.

Testing without knowing how doesthe program works.

Testing with the tester that knowseverything about the program.

Test by looking only at the

requirements statement.

Test to ensure that every single

instruction and possible situationhave been tested.


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Examples of problem solving

Problem Statement #1:

Compute and display the total cost of apples byreceiving the number of kilograms of applespurchased and the cost per kilogram of apples.

Step 1: Understand the problem

Input number of apples purchased (numKiloApples), cost per kilogram

of apples (costPerkg)

Process formula total cost = cost per kilogram of apples x number of

apples kilograms (totalCost= numKiloApples x costPerkg)

Output Total cost of purchased apples (totalCost)

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Step 2: Develop the solution

(pseudo code)

Algorithm cost of apples purchased

Get number of kilogram ofapples purchased

Get cost per kilogram of apples

Compute the total cost of apples

The total cost of apples is number of kilogram ofapples purchased multiply/times cost per kilogram

Display the total cost

End algorithm


Input number of applespurchased (numKiloApples), costper kilogram of apples(costPerkg)

Process formula total cost = costper kilogram of apples x numberof apples kilograms (totalCost=numKiloApples x costPerkg)

Output total cost of purchasedapples (totalCost)

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Step 2: Develop the solution (flowchart)

Step 3: Write the program(C++ codes)

Start

Read kilograms of apples(numKiloApples)

Compute the total cost of apple purchased,

totalCost= numKiloApples x costPerkg

PrintTotal cost of apples

in RM (totalCost)

End

Get cost per kilogram ofapples (costPerkg)

void main()

{

int numKiloApples;int costPerkg;

int totalCost;

cout > costPerkg;

totalCost = numKiloApples * costPerkg;

cout >> The total cost of apples is >> totalCost;}

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During the promotion of Ummies Boutique, 30%discount is given to every item purchased. Write aprogram to compute and display the price afterdiscount for every item purchased by the customers.


Input Price of the item,priceBefore

Process

formula discount = priceBefore x 0.3

formula priceAfter = priceBefore - discount

Output Price after discount,priceAfter

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(pseudo code)

Algorithm price after discounted

get the price of the item (priceBefore)compute the price of the item after discount

compute discount = priceBefore x 0.3

compute priceAfter = priceBefore - discount

display the the price after discount, priceAfter

End algorithm



Processdiscount = priceBefore x 0.3

priceAfter = priceBefore discount


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Start

Get Items price (priceBefore)

Compute the price after discount

priceAfter = priceBefore discPrice

Display the price afterdiscount, priceAfter

End

Compute the discountdiscPrice = priceBefore x 0.3 void main()

{

float priceBefore;

float discPrice;

float priceAfter;

cout

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Flowchart with different structure

If/else double-selection structure:

Pseudo code:If students grade is greater than or equal to 60

Print Passed

ElsePrint Failed

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Flowchart with different structure

If/else double-selection structure:

Pseudo code:While product is less than or equal to 1000

Multiply product by two

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SHN Enterprise is given 10% discount for every itemwith price of above RM100 only. Write a program thatcompute and display the price after discount forevery item purchased by the customers.



Process

formula discount = priceBefore x 0.1

formula priceAfter = priceBefore discount


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(pseudo code)

Algorithm price after discounted

get the price of the item, priceBeforecompute the item discount

if priceBefore > 100

compute discount = priceBefore x 0.1

else

discount = 0

compute priceAfter = priceBefore discountdisplay the price after discount, priceAfter

End algorithm


Inputs Price of the item,priceBefore

Processdiscount = priceBefore x 0.1

priceAfter = priceBefore discount


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Start

Discount = priceBefore x 0.1

Get Items price, priceBefore

Display price afterdiscount, priceAfter

End

Compute the price after discount

priceAfter = priceBefore - discount

priceBefore > 100?

discount = 0

YesNo

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void main()

{

float priceBefore;

float discPrice;

float priceAfter;

cout

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Indent program properly

Use a good indentation style to enhance the readability of aprogram.

The layout of a program should make it easy for a reader toidentify the program's modules.

Use blank lines to offset each function.

Also, within both functions and the main program, you shouldoffset with blank lines and indent individual blocks of code visibly.

These blocks are generally - but are not limited to - the actionsperformed within a control structure, such as a while loop or an if

statement.

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Any questions..?

End of Lecture 2..

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