Design withStructure Charts

Design Process

• Problem solving and design should be done independent of programming.

• Code significantly clouds the design process.. It is very difficult to see the design and address design issues when coding

• Design needs to take place in a mode which minimizes code influence

4 Steps

Create a structure chart based on the main

item,NOT programming

requirements

1

Modify structure chart based on the programming requirements.

Top-down design.

2

Write code toimplement the

top-down design.As you mature thiswill be skipped by

going to step 4.

3

Improve readabililtyof the code by incorporating

functions.

4

National Parcel ExampleExample 2 : Parcel Service Company.

Emphasizes IF notation for top down design.

National Parcel Service (NPS) specializes in nationwide delivery of small packages. NPS will not accept

any packages whose largest dimension is greater than 3 feet or whose weight exceeds 50 pounds.

The charge for shipping a parcel is $0.75 plus an amount based on package weight as follows:

Weight (lb.) Rate-----------------------------20 or less $0.08 per lb.40 or less $0.10 per lb.Over 40 $0.15 per lb.-----------------------------

There is an additional $1.00 charge if the volume of the package exceeds 18 cubic feet. Write a program

that will read the dimensions of a parcel (in feet) and its weight (in pounds) and then compute and print

the postage due. If the package is rejected, an appropriate message should be printed.

Example Test Data Length Width Depth Weight 1.5 1.2 0.8 6.0

Parcel Delivery

National Parcel Service

Parcel *

Acceptable Not Acceptable

Shipping Status

Charge

Weight Charge Volume Charge 0.75

Wt<=20 20<Wt<=40 Wt>40 Vol<=18 Vol>18

WeightSize

Length Width Depth

Change in Perspective

• Our natural view of the problem domain may not match the requirements.

• There are multiple views of anything.

• Other views are not wrong, but do provide insight into the structure we expect and perceive.

• In this problem we need to adjust for a single parcel.

Parcel Delivery(adjust to one package)

Parcel

Acceptable Not Acceptable

Shipping Status

Charge

Weight Charge Volume Charge 0.75

Wt<=20 20<Wt<=40 Wt>40 Vol<=18 Vol>18

WeightSize

Length Width Depth

TV SurveyExample 3 : Television Rating Service

Emphasizes WHILE notation for top down design

A television rating service makes a survey of the viewing audience to sample the popularity of tv shows.

When a call is made concerning a particular show, the sex and age of the person called, as well as whether

or not the person watches the program regularly, are recorded. Write a program that will process the data

gathered for the show. The total number of people called, the number who said they watched the show

regularly, and the percentage of those who watch the show on a regular basis should be printed. The

program should also print a table showing the percentages of those who watch the show by sex and age

categories. The output table should look something like the sample shown here.

SEX UNDER 18 18 to 35 36 to 55 OVER 55 ------------------------------------------------------------------MALE 12.2% 47.5% 34.3% 6.0%FEMALE 18.5% 32.4% 35.6% 13.5%------------------------------------------------------------------

TV Survey

Survey

Call *

Regular Not Regular

Viewer StatusSex

Male Female

Age<18 18<=Age<36 Age>5536<=Age<55

Age

Requirements demandadjusting view

• Sex and age are typically related only through the person, not as subcategories.

• This problem views them as subcategories of one another.

• It doesn’t make any difference which is a subcategory of the other.

• Next slide shows an adjusted view.

TV Survey

Survey

Call *

Regular Not Regular

Viewer Status

Sex

Male Female

Same as MaleAge<18 18<=Age<36 Age>5536<=Age<55

Step 2

Adapt the structure chart

to accommodate the

program specifications:

DO A TOP-DOWN DESIGN

Parcel DeliveryAdjusting Structure Chart for Program (Top-Down) Design

Compute Postage

Acceptable Not Acceptable

Determine Acceptability

Compute Charge

ComputeWeight Charge

ComputeVolume Charge

ComputeTotal Charge

Wt<=20 20<Wt<=40 Wt>40 Vol<=18 Vol>18

WeightSize

Length Width Depth

Input Package Info

Output ChargeOutput Rejection

Message

Wt_chrg=Wt*0.08

Wt_chrg=Wt*0.1

Wt_chrg=Wt*0.15

Vol_chrg=0.0

Vol_chrg=1.0

Charge=Wt_Chrg+Vol_Chrg+

0.75

TV SurveyStructure Chart Conversion to Top Down Design

Summarize Survey

Process Call *

Regular Not Regular

Process Regular Viewers

Sex

Male Female

Same as Malebut use WL18,

WL36,...

Age<18 18<=Age<36 Age>5536<=Age<55

Initializations Output Report

Calculate % Write ReportInput Call Info Count # of Calls

Count RegularViewer

IncrementML18

IncrementML36

IncrementML55

IncrementMG55

Step 3

Write code to implement

the design

#include <iostream.h>main (){ float length,width,height,weight,WtChrg, volume,VolChrg,TotalCharge; // input package information cout << " Enter length, width and height of package\n"; cin >> length >> width >> height; cout << " Enter weight of package\n"; cin >> weight; // determine acceptability if ( (length<3) && (height<3) && (width<3) && (weight<50)) { // ACCEPTABLE // COMPUTE CHARGE // WEIGHT CHARGE if (weight<=20) WtChrg = 0.08*weight; else if (weight<=40) WtChrg = 0.10*weight; else WtChrg = 0.15*weight; // VOLUME CHARGE volume = length*width*height; if (volume > 18.0) VolChrg = 1.0; else VolChrg = 0.0; // TOTAL CHARGE TotalCharge = 0.75 + WtChrg + VolChrg; // OUTPUT CHARGE cout << "Total charge for the package is " << TotalCharge << endl; } else // NOT ACCEPTABLE { cout << "Package EXCEEDS weight/size specs for shipment\n"; cout << "...... Try another company!"; } }

ParcelDelivery

Implementation

#include <iostream.h>main (){ char sex, regular; float PercentRegular; int age, rv, tv, num_read, NumberToRead; int ml18,ml36,ml55,mg55,fl18,fl36,fl55,fg55; // initializations tv=0; rv=0; ml18=0;ml36=0;ml55=0;mg55=0; fl18=0;fl36=0;fl55=0;fg55=0; cin >> NumberToRead; num_read = 0;

while (num_read < NumberToRead) { // PROCESS CALL // input call information cin >> sex >> age >> regular; // count number of calls tv++; num_read++; // process regular viewer if ( (regular == 'R') || (regular == 'r')) { // count as a regular viewer rv++; // tabulate age/sex info if ( (sex == 'M') || (sex == 'm')) { // process Male if (age < 18) ml18++; else if (age < 36) ml36++; else if (age < 55) ml55++; else mg55++; } else { // process Female if (age < 18) fl18++; else if (age < 36) fl36++; else if (age < 55) fl55++; else fg55++; } } } // loop PercentRegular=rv / tv; // write reports to output device // ........} // end

TVSurvey

Implementation

Step 4

Use FUNCTIONS to implement

the design

// FUNCTIONSint Acceptable(float length, float height, float width, float weight){ return ( (length<3) && (height<3) && (width<3) && (weight<50) );} float WtChrg(float weight){ float wc; if (weight<=20) wc = 0.08*weight; else if (weight<=40) wc = 0.10*weight; else wc = 0.15*weight; return wc;} float PackageVolume(float length, float height, float width){ return length*height*width;} float VolChrg(float v){ float vcharge; if (v > 18.0) vcharge = 1.0; else vcharge = 0.0; return vcharge;} void Reject() { cout << "Package EXCEEDS weight/size specs for shipment"; cout << " ...... Try another company!"; }

#include <iostream.h>

// PROTOTYPESint Acceptable(float length, float height, float width, float weight);

float WtChrg(float weight);

float PackageVolume(float length, float height, float width);

float VolChrg(float v);

void Reject();

// MAIN ROUTINEmain (){ float length,width,height,weight,volume,TotalCharge; // input package information cout << " Enter length, width and height of package\n"; cin >> length >> width >> height; cout << " Enter weight of package\n"; cin >> weight; // determine acceptability if ( Acceptable(length,height,width,weight)) { // ACCEPTABLE volume = PackageVolume(length,width,height); TotalCharge = 0.75 + WtChrg(weight) + VolChrg(volume); cout << "Total charge for the package is " << TotalCharge << endl; } else // NOT ACCEPTABLE Reject(); }

Parcel DeliveryImplementation

w/functions

TV SurveyImplementation

w/functions

It’s Your Turn!