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Problem Solving with the Sequential Logic Structure

Lesson 5

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Overview

• Algorithm Instructions• Sequential Logic Structure• Solution Development

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Flowchart Symbols

• Terminal– Starts, Stops, Ends

• Input/Output– Input data, Output information

• Assign– Apply values to variables

• Process– Execute instructions

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Terminal

Input/Output

Assign

Process

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Sequential Logic Structure

• The oldest logic structure• The most used logic structure• The easiest structure to understand• Is one statement after another

statement, after another statement, after another statement, etc.

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Examples

• Enter Name• Enter Address• Enter City• Enter State• Enter Zip• Enter Hours• Enter Wage• Pay = Hours * Wage

• Print Name• Print Address• Print City• Print State• Print Zip• Print Pay

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Let’s work a problem…

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The Problem…

• Sadie invests $5,000 in a savings account that yields 5% (.05) annual interest.

• Assuming that all interest is left on deposit along with the original deposited amount– What will be the equation to calculate the

amount that will be in the account at the end of 10 years?

– How much will the interest be at the end of the 10 years?

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The Solution

• First: Research banking algorithms– We wind up with Two Equations:

• First…the Tough one– Amount = Principal * ((1 + Interest Rate) ^ Time)

» Principal – amount to be invested» Interest Rate – yearly percentage rate » Time – investment period in years» Amount – principal + interest earned

• Next…the Easy one– Interest = Amount – Principal

» Interest – the actual amount of Interest

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Structure Chart of Solution

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Calculate Savings

Get input Calculate

PrintAmount

PrintInterest

CalculateInterest

CalculateAmount

Print

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Pseudocode Solution

• Get Principal Amount • Get Yearly Interest Rate • Get Time Intervals • Calculate Amount of Principal + Interest

– Amount = Principal * ((1 + Rate) ^ Time)• Calculate Amount of Interest

– Interest = Amount - Principal• Print Amount of Ending Principal + Interest• Print Amount of Interest

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Coding the Problem

In Visual Basic

Note: Up to this point it didn’t matter what language we use…

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Data Dictionary

Variable Name Data Type Module Defined Domain Scope

Principal Decimal GetInputCalculate

0 < n < 1 million Global

InterestRate Double GetInputCalculate

0 < n < 1 to 14+ digits

Global

Time Short GetInputCalculate

0 < n < 32,767 Global

Amount Single CalculatePrintResult

0 < n < 1 million Global

Interest Single CalculatePrintResult

0 < n < 1 million Global

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VB Solution – Declare Variables

' Input Values by UserDim Principal As DecimalDim InterestRate As DoubleDim Time As Short

' Output ValuesDim Amount As SingleDim Interest As Single

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Internal Documentation

taking the form of Comments

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VB Solution – Get Input

Private Sub cmdGetInput_Click()Principal = CDec(InputBox("In Dollar amount " & _

“ (5000)", "Please Enter Principal Amount"))

InterestRate = CDbl(InputBox(" Ex. 5% " & _ “ would be entered as .05", "Please " & _ “ Enter Annual Interest Rate"))

Time = CShort(InputBox("An Integer " & _ “ with no decimals", "Please Enter Length "

& _ “ of Time in Years"))

End SubMcManus

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VB Solution – Calculate Result

Private Sub cmdCalculate_Click()

' Calculates Principal + Interest over timeAmount = Principal * ((1 + InterestRate) ^ Time)

' Calculates amount of total Interest at end of' time period

Interest = Amount - Principal

End Sub

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VB Solution – Produce Output

Private Sub cmdPrintResult_Click() lstOutput.Items.Add(" The Amount of Principal + " & _

“Interest Paid on") lstOutput.Items.Add(" the Principal Amount of " & _ VB6.Format(Principal, "Currency") & " for ") lstOutput.Items.Add(Time & " years is") lstOutput.Items.Add(" " & _

VB6.Format(Amount, "Currency")) lstOutput.Items.Add(" and the Amount of Interest is") lstOutput.Items.Add(" " & _

VB6.Format(Interest, "Currency"))

End Sub

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VB Solution – the Form

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Getting the Input

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1st step

2nd step

3rd step

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Calculating the Solution

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VB Solution – the Output

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Documentation

• Internal Documentation– Takes the form of comments within the

program– Helped by using Mnemonic terms

• Creates self-documenting code

• External Documentation– Takes the form of

• User Manuals• Help Screens• System Documentation

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Testing the Solution

• Input Variables to be tested– Principal

• any numeric value greater than 0– InterestRate

• any numeric value greater than 0 and less than 1– Time

• any integer greater than 0

• Note: We didn’t do any Error checking in this problem.

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Testing the Solution

• Output Variables– Would expect to see the Amount a

positive number greater than the Principal amount

– Would expect to see the Interest greater than zero.

• Why are these statements important?

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Summary

• Analyze the problem– Being able to restate the problem is one

indicator that you understand the problem• Develop the structure chart• Develop the algorithms• Develop the data dictionary• Develop the code• Test the solution

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Next?

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