Unit 3 Self-Check Questions

AAP-3.B.5

Imagine you are using a procedure calculate_area(length, width) to find the area of rectangles. Which action demonstrates the benefit of using parameters in this procedure?

You can use the same procedure with different length and width values to calculate the area of various rectangles.

Correct! Parameters allow reuse of the function with different inputs.

The parameters length and width can now be used as variable names everywhere in your program.

Parameters are local to the procedure. They are only defined within the procedure.

You can allow the user to change the name of the variables length and width.

Variable names don’t change how the program works.

You can use the same length and width values for every rectangle in the program.

This contradicts the purpose of using parameters - you don’t need to make these values parameters if the arguments are always the same.

from Lab 1, Page 4

AAP-3.B.1

Imagine you are developing a program that calculates the total cost of a shopping cart after applying a discount and taxes. Your team has created a function below that performs one step of this task. Which of the following demonstrates procedural abstraction in this scenario?

PROCEDURE calculate_tax(cart, tax_rate)

Using the

calculate_tax

function without knowing the specific math operations inside it.

Correct! Procedural abstraction allows using a function without needing to understand its implementation. You only need to know what it does, not how it does it.

Reading through the function code to determine how it works so you can write your own version.

Using the version already written by your team would demonstrate procedural abstraction. Procedural abstraction means you can use the function without knowing exactly how it works inside.

Declaring

cart

and

tax_rate

variables outside of the function and using those variables when calling the function.

A variable is a form of abstraction that holds values, but procedural abstraction refers to the benefit of the procedure itself.

This is not a good example of procedural abstraction. Your team should not be writing a procedure to perform just one step of the task.

Breaking larger programs into smaller pieces is a part of procedural abstraction.

from Lab 1, Page 4

AAP-1.A.2

You are reviewing the following two snippets of code written by a classmate:

Code 1:

x ← 5
y ← 3
z ← x * y  
DISPLAY(z)

Code 2:

length ← 5  
width ← 3  
area ← length * width  
DISPLAY(area)

Which statement best explains why Code 2 is preferable?

It runs faster than Code 1.

Variable names do not affect execution speed.

It uses meaningful variable names, making it easier to understand.

Correct! Descriptive names improve readability and comprehension.

It uses more variables, making the program more generalizable.

Both codes use the same number of variables.

There is nothing to make Code 2 preferable to Code 1.

Code 2 is preferable due to better readability.

from Lab 2, Page 1

AAP-1.D.3.C

Why are abstract data types (ADTs) used in programming? Choose all that apply.

To make the code run faster.

Abstract data types improve organization and abstraction, not speed.

To hide complexity and provide a custom interface for managing data.

Correct! Abstract data types simplify data handling and can help hide implementation details.

To eliminate the need for conditional statements.

Abstract data types do not remove the need for conditionals.

To eliminate the need for debugging.

Abstract data types do not prevent all bugs.

from Lab 2, Page 2

CRD-2.C.3.A, CRD-2.D.3.A

This question is about identifying inputs and outputs.
Imagine you are working on a program for a smart home thermostat. The thermostat uses a temperature sensor to monitor the current room temperature and sends a message to a heating system to adjust the temperature. Below is a flow diagram of the logic of the program code that controls the thermostat.
$start -> read current_temp -> read desired_temp -> current_temp < desired_temp? {true -> report turn heating system ON} {false -> report turn heating system OFF}$ Based on the thermostat program described in the flowchart, determine whether the following statements are true or false.

The current room temperature is an input to the program.
The desired temperature set by the user is an output from the program.
A message sent to the heating system to turn ON or turn OFF is an output of the program.
The room temperature increasing or decreasing is an output of the program.

True, True, True, False

The desired temperature set by the user is an input, not an output.

True, False, True, False

Correct! The program reads the current temperature from a sensor and outputs a control signal to the heating system.

True, False, False, True

The output of this program is the message sent to the heating system to turn ON or OFF, not the change in temperature.

False, False, True, False

Both the current room temperature and the desired temperature are inputs to the program.

from Lab 2, Page 5

Which of the following statements are true about this list?
set (words and numbers) to {rabbit, 5, benefit, is, 34, kite, 2, 305, the, 61}

map (letter (1) of ()) over (words and numbers)

reports the list {r, 5, b, i, 3, k, 2, 3, t, 6}.

Correct.

map (item (1) of ()) over (words and numbers)

reports the list {rabbit}.

The blank space in item of expects a list as its input, but map puts a single item from words and numbers into that slot.

Both of the above.

The input list (words and numbers) contains text strings (not lists) so the blank space in the input function should expect a text string (not a list).

None of the above.

Map performs the input function over each item in the input list.

from Lab 2, Page 5

Which of the following statements are true about this list?
set (capitals) to {{Augusta, Maine}, {Boise, Idaho}, {Columbia, South Carolina}, {Des Moines, Iowa}}

Choose all that apply.

Why not use an ADT?

The list inside a list shown above makes it clearest to you now as you answer this self-check item what the structure is, but you're right, in an actual program it would be better to use an abstract data type:

reports the list {Augusta, Boise, Columbia, Des Moines}.

Correct.

reports the list {Augusta, Maine}.

No. Map performs the input function on each item of the list—not on the whole list. The expression item (1) of (capitals) (without using map at all) would report the list {Augusta, Maine}.

reports the list {A, B, C, D}.

No. You can find the first letter of a word, but not the first letter of a list. The expression map (letter (1) of (item (1) of ( ))) over (capitals) would report the list {A, B, C, D}.

map (all but first of ()) over (capitals)

reports the list {Maine, Idaho, South Carolina, Iowa}.

No. This is a tricky one. What gets reported is actually a list of one-item lists: {{Maine}, {Idaho}, {South Carolina}, {Iowa}}. You might want to try it in Snap!. The expression map (item (2) of ()) over (capitals) would report the list {Maine, Idaho, South Carolina, Iowa}.

reports the list {{Boise, Idaho}, {Columbia, South Carolina}, {Des Moines, Iowa}}.

No. Map performs the input function on each item of the list—not on the whole list. The expression all but first of (capitals) (without using map at all) would report the list of lists {{Boise, Idaho}, {Columbia, South Carolina}, {Des Moines, Iowa}}.

from Lab 2, Page 5

Consider this list of squares:
set (squares) to {1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225}
Which of the following expressions will report a list? Choose all that apply.

Correct.

Correct.

No, + reports a number, so in this case combine will report a number.

keep items (letter (length of ()) of () = 1) from (squares)

Correct.

combine (squares) using (join ()()) items of

No. join(1,4) will report 14.

Correct.

Lab 1: Dealing with Complexity

Lab 2: Contact List