PT1420 Unit 4 Assignment 1 Homework

Short Answer 1-7 on page 111
1. How do modules help you to reuse code in a program?
If a operation needs to be performed in several places, the same module can be called and re-used cutting down on unnecessary code.

2. Name and describe the two parts that a module definition has in most languages.
The two parts are a header and a body

3. When a module is executing, what happens when the end of the module is reached?
It jumps back to the part of the program that called it. This is known as the return point

4. What is a local variable? What statements are able to access a local variable?
A local variable is declared inside a module and cannot be accessed by statements that are outside the module.

5. In most languages, where does a local variable’s scope begin and end?
Usually begins at the variables declaration and ends at the end of the module

6. What is the difference between passing an argument by value and passing it by reference?
Passing an argument by value copies the data from the variable but does not change the original data. Passing a variable by reference will overwrite the existing data at that reference point in memory.

7. Why do global variables make a program difficult ot debug?
If there is a debug issue, you have to step through ALL modules looking for the module that is incorrectly accessing that variable. Most programs have many many modules. This makes global variables very time consuming to debug.

Algorithm Workbench Review Questions 1,5,6, and 7 from page 111

1. Design a module named timesTen. The module should accept an Integer argument. When this module is called, it should display the product of its argument multiplied by 10

1. Declare a variable called number and set the value of it
2. Call the module timesTen passing as an argument the variable number by reference
3. In the module named timesTen create a parameter named number that the argument will be passed into
4. Calculate and set the variable number * 10
5. Display the variable number

5. Design a module named getNumber, which uses a reference parameter variable to accept an Integer argument. The module should prompt the user to enter a number and then store the input in the reference parameter variable

Module main()

Declare integer number
Call getNumber(number)
Display “Your number is” number
End Module
Module.getNumber(Ref number) Display “Please enter a number” Input number
End Module

6. What will the following pseudocode program display?
Module main() Declare Integer x =1 Declare Real y = 3.4 Display x, “ “, Y Call changeUs(x, y) Display x, “ “, y
End Module
Module changeUs(Integer a, real b) Set a = 0 Set b = 0 Display a, “ “, b
End Module
This will display 1, 3.4

7. What will the following pseudocode program display?
Module main() Declare integer x =1 Declare Real y = 3.4 Display x, “ “, y Call changeUS(x, y) Display x, “ “, y
End Module
Module changeUs(integer ref a, real ref b)
Set a = 0
Set b = 0.0
Display a, “ “, b
End Module
The display on this pseudocode would be.
1, 3.4
0, 0.0
0, 0.0

Programming Exercises 1 and 2 page 113
1. Kilometer Converter
Design a modular program that asks the user to enter a distance in kilometers, and then converts that distance to miles. The conversion formula is Miles= Kilometers * 0.6214
Module main()
Declare real km =0
Declare real miles =0
Call getKM(km)
Call doCalc(km, miles)
Call displayMiles(km, miles)
End Module
Module getKM(Ref Real KM) Display “Please enter the Kilometers” set km
End Module
Module doCalc(Value real km, Ref real miles) Set miles = km * 0.6214
End Module
Module displayMiles(value real km, value real miles)
Display “You entered” km “Kilometers”
Display “That converts to” miles “Miles”
End Module

2. Sales Tax Program Refactoring
ReWrite sales tax program from chapter 2 into module design
Module main() Declare real purchaseAmount = 0 Declare real constant stateTax = .04 Declare real constant countyTax = .02 Declare real StateTotalTax = 0 Declare real CountyTotalTax = 0 Declare real TotalTax = 0 Declare real total = 0 Call getPurchaseAmount(purchaseAmount) Call doCalc(purchaseAmount, stateTax, StateTotalTax, countyTax, CountyTotalTax TotalTax, total) Call displayTotals(purchaseAmount, StateTotalTax, CountyTotalTax, TotalTax, total)
End Sub
Module getPurchaseAmount(Ref real purchaseAmount) Display “Enter the Purchase amount” Set purchaseAmount
End Sub
Module doCalc(Value real purchaseAmount, Value const stateTax, Ref real StateTotalTax, Value const countyTax, Ref real CountyTaxTotal, Ref real TotalTax, Ref real total) Set StateTotalTax = purchaseAmount * stateTax Set CountyTotalTax = purchaseAmount * countyTax Set TotalTax = StateTotalTax + CountyTotalTax Set total = TotalTax + purchaseAmount
End Module
Module displayTotals(value real purchaseAmount, value real StateTotalTax, value real CountyTotalTax, value real TotalTax, value real total) Display “Your purchase amount is” purchaseAmount Display “The total state tax is” StateTotalTax Display “The total county tax is” CountyTotalTax Display “TheTotal Tax amount is” TotalTax Display “Your Purchase Total is” total
End Sub