Unit 2 Self-Check Questions

from Lab 1, Page 1

Examples like this one are useful to test your understanding of assignment to variables, but you wouldn't use a sequence of assignments like this in an actual program.

What value will this code display?

a ← 3
b ← a
a ← 4
DISPLAY(b)

3

Correct! The variable b is assigned the value of the variable a (which is 3 when

b ← a

is done).

4

The variable b is given the value of the variable a (which is 3 when

b ← a

is done); b doesn't remember that the 3 came from a so it doesn't change when a is changed.

a

The variable b has been set to the value of the variable a, not the letter "a" itself.

b

The script will display the value of the variable b, not the letter "b" itself.

from Lab 1, Page 1

What value will this script report?
set m to 9, set k to 5, set m to (m + 1), set k to (k - m), report k

-5

Correct!

3

The value of the variable m is always greater than the value of the variable k in this script, so subtracting m from k will give a negative number.

-4

The value of the variable m is 9 at the beginning, but it has been changed by the time it is subtracted from k.

5

The last set command sets the value of the variable k to the value k – m, not m – k.

from Lab 1, Page 2

We really shouldn't be encouraging students to mutate a block's inputs. There are really two issues here; one is with the x=x+1 style of programming altogether, and the second is that formal parameters specifically shouldn't generally be mutated; it's better to make a script variable that's initialized to the input value. (If we change this, we need to update the Guided Notes.) --MF, 6/26/21 with BH

mystery function (input):
if (input < 5) (repeat until (input = 5)
(
say (input) for (1) secs,
set (input) to (input + 1)
)
report (finished)

Which inputs to mystery function will report "finished"?

Any integer

Correct! No matter what the input number is (as long as it's an integer), the report block will eventually run. (This doesn't necessarily happen in every procedure, but here it will.)

Only integers greater than or equal to 5

Write out some examples of what happens when the input is less than 5. For example, if the input is 3, the sprite will say 3, the input will be changed to 4, the sprite will say 4, the input will be changed to 5, the repeat until loop will stop, and the function will report "finished."

Only integers less than 5

The report command isn't inside the if.

Only 5

The repeat until block checks the value of input every time through the loop, not just its initial value.

from Lab 1, Page 2

What will the sprite say if you run the same function with the input 1?

It does say 4 at the end, but it says other things before that.

How does repeat until work?

four speech bubbles saying '1', '2', '3', and then '4'

Correct! The repeat until block runs the code in its script slot until input = 5, then the computer skips down to the next command, report (finished), without the sprite ever saying 5.

five speech bubbles saying '1', '2', '3', '4', and then '5'

The repeat until block tests the value of input before running the code in its script slot.

The feedback is not finished because I realized that BH might object to changing the value of an input variable... --MF, 3/1/19

from Lab 1, Page 2

What will happen if you run the same function with the input 9?

The sprite will say 9, and the block will report "finished."

What does the if block do when input is 9?

The sprite will say 9, 8, 7, 6, and the block will report "finished."

What does the set instruction do to the value of input?

The sprite will say 9, 10, 11, 12, 13, … and keep counting, and the block will never report "finished."

When input is 9, will the code inside the if command run?

The sprite will say nothing, and the block will report "finished."

Correct! The code inside the if command will not run.

The feedback is not finished because I realized that BH might object to changing the value of an input variable... --MF, 3/1/19

from Lab 1, Page 5

AAP-2.N part b

Which of the following blocks will report a list of length 3?

Choose all that apply.

No, this makes a list of one item, even though it has more than a single word.

No, item 3 of the list is the word "kiwi" which isn't a list at all.

item 2 of {lemon, {pineapple, strawberry, kiwi}}

This is one of the two correct answers.

This is one of the two correct answers.

from Lab 2, Page 2

Imagine you make a variable capitals and use set to give this list of lists a name:
set (capitals) to {{Augusta, Maine}, {Boise, Idaho}, {Columbia, South Carolina}, {Des Moines, Iowa}}
Which of the following statements are true?

Choose all that apply.

reports a list with two items: "Augusta" and "Maine".

Correct.

reports the word "Augusta".

Correct.

reports the word "Iowa".

No. What is item 2 of "capitals"?

reports the number 8.

No. Each of the small lists is a single item in the list "capitals" .

all but first of (item (last) of (capitals))

reports a list with one item: "Iowa".

Correct.

reports the string "Boise".

The items of capitals are lists.

item (last) of (all but first of (capitals))

reports the string "Iowa".

The items of all but first of (capitals) are lists.

reports the number 2.

Correct.

from Lab 2, Page 3

Which of the scripts below will produce the following sprite behavior?
sprite saying Abraham then Lincoln
(When you run the script, though, it actually says Abraham Lincoln only once.)

Choose all that apply.

for each (item) of {Abraham, Lincoln} [say (item) for (1) secs]

Correct.

No, when a sprite says a list, we see a visual representation of the list.

say (item (1) of {Abraham Lincoln, George Washington, Barack Obama}) for (2) secs

No, this says "Abraham Lincoln" all at once, not in two separate speech balloons.

say (item (1) of {Abraham, George, Barack} for (1) secs, then say (item (1) of {Lincoln, Washington, Obama} for (1) secs

Correct.

from Lab 2, Page 3

AAP-2.O part b

inputList ← [3, -1, 2, 10, -5]

FOR EACH item IN inputList
{
  IF(item > 0  AND  item * item > 4)
  {
    DISPLAY(item)
  }
}

What will be displayed as a result of running the code segment given?

9, 1, 4, 100, 25

What does the

IF

instruction test? What does the

DISPLAY

instruction in this code display?

9, 100

What does the

DISPLAY

instruction in this code display?

3, 2, 10

Is 2 * 2 > 4 ?

3, 10

Correct!

from Lab 2, Page 3

PROCEDURE Mystery(numberList, targetNumber)
{
  counter ← 0
  FOR EACH number IN numberList
  {
    IF(number > targetNumber)
    {
      counter ← counter + 1
    }
  }
  RETURN(counter)
}
myMathGrades ← [100, 80, 90, 80, 60, 100, 50, 100]
Mystery(myMathGrades, 60)

What will be returned if the code above is run?

[100, 80, 90, 80, 100, 100]

What type of value does the procedure return?

7

Is 60 > 60 ?

6

Correct!

60

What is the procedure doing?

from Lab 3, Page 1

AAP-2.E.4B

Consider the following code segment.
set (password) to (secret); ask (What is the password?) and wait; if (answer) ≠ (password) {say (Access denied!)} else {say (Access granted!)}

If a user enters "password123," what will be the output?

Access granted!

"password123" does not match "secret" so the if condition is true.

Access denied!

Correct! Since "password123" does not equal "secret," the if condition is true, and "Access denied!" is displayed.

No output; there will be an error message.

This code will run without errors and always produces output.

No output; the code does not provide an output for this situation.

The code handles all inputs and always says either "Access granted!" or "Access denied!"

from Lab 3, Page 1

AAP-2.L.1D

Do the following code segments produce the same outcome?
if (xposition) < (100) {set pen color to (blue)} else {set pen color to (yellow)}

if (xposition) > (100) {set pen color to (yellow)} else {set pen color to (blue)}

No, wherever one code segment sets the pen color to blue, the other sets the pen color to yellow (and vice versa).

In most cases, the two code segments will set the pen color to the same color. Notice the two code segments have different inequality signs (one is less than, the other is greater than).

No, they have different outcomes when the x position of the sprite is 100.

Correct! For "if x position less than 100," the else condition will run when x = 100 (and the pen color will be yellow). Similarly, for "if x position greater than 100," the else condition will run when x = 100 (and the pen color will be blue).

Yes, the outcome for both segments is no change; the pen color will never change.

In both code segments, the pen color will change based on the sprite's x position.

Yes, wherever one code segment sets the pen color to blue, the other does too (and likewise for yellow).

This is true except when the sprite's x position is exactly 100.

from Lab 3, Page 2

There's no built in ≤ block in Snap!. Suppose we wanted to build one. Which two of the following Boolean expressions are equivalent to the expression num less than or equal to 23 predicate

?

Can num be both less than 23 and equal to 23 at the same time?

Correct! This picture shows an expression that will report true if num is less than or equal to 23.

Correct! If num is not greater than 23, then it is either less than 23 or equal to 23.

Imagine that the value of num is 22.5. Will this expression and the expression given in the question report the same response?

from Lab 3, Page 2

Which of the following expressions will report true?

I only

II only

I and II

Neither I nor II

from Lab 3, Page 3

AAP-2.I.4.B

You are working on a weather application that categorizes outdoor conditions based on temperature (in Fahrenheit) and humidity (as a percentage). The following code is used to determine whether it is "Hot and Humid," "Hot and Dry," "Cool and Humid," or "Cool and Dry."
if (temperature > 70) { if (humidity > 50) {set output to Hot and Humid} else {set output to Hot and Dry}} else { if (humdidity > 50) {set output to Cool and Humid} else {set output to Cool and Dry}}

Suppose your app's sensors detect a temperature of 60°F and a humidity of 40%. What will be the program output?

Hot and Humid

The temperature of 60°F does not satisfy the temperature > 70 condition.

Hot and Dry

The temperature of 60°F does not satisfy the temperature > 70 condition.

Cool and Humid

The temperature ≤ 70 but the humidity is 40%, which does not satisfy the humidity > 50 condition.

Cool and Dry

Correct! The temperature ≤ 70 and the humidity ≤ 50.

from Lab 3, Page 5

AAP-2.E

What would you put into the gray ring to find all the items in the list that start with the letter “a”?

keep items ([gray ring]) from (list(apple, banana, orange, grape))

This code only checks the first letter of the single character "a" (which is "a"), not the list items.

Correct! This code correctly extracts the first letter of each item in the list and checks if it is "a."

This code gives an error because it tries to compute, e.g., ITEM 1 of (APPLE), but APPLE isn’t a list.

This syntax is invalid for checking the first letter of each list item. This code looks for the first letter of an empty list.

from Lab 3, Page 5

AAP-2.E

Which of the following items, if in mystery list, would be in the list reported by this block? Choose all that apply.
keep items (not(is () a number?) and (length of text() > 10)) from (mystery list)

keep items (not(is () a number?) and (length of text() > 10)) from (mystery list)

A number with more than 10 digits.

The item cannot be a number.

A number with fewer than 10 digits.

The item cannot be a number.

A mix of numbers and letters that is more than 10 characters long.

Correct! A mix of numbers of letters is not a number and the length > 10. (Did you find all the correct answers?)

A five-word sentence made of words that are each 2 or 3 letters long.

Correct! This is not a number and the length > 10. (Did you find all the correct answers?)

A phrase that is less than 10 characters long.

The item cannot be less than 10 characters.

Any phrase that does not contain any numbers.

The phrase has to be more than 10 characters.

A 16-character password with numbers, letters, and symbols.

Correct! This is not a number and the length > 10. (Did you find all the correct answers?)

A long word with more than 10 letters, like "comprehensible."

Correct! This is not a number and the length > 10. (Did you find all the correct answers?)

from Lab 4, Page 1

AAP-2.L.2

Algorithms that look the same may have different results. The following incomplete code fragment was designed to test if

number

is odd:

IF (MISSING CONDITION)
{
  DISPLAY "It is odd."
}

Which of the following can be used in place of the MISSING CONDITION?

number MOD 1 = 0

MOD

returns the remainder when the first input is divided by the second. Whether a number is odd or even depends on divisibility by 2.

number MOD 1 = 1

MOD

returns the remainder when the first input is divided by the second. Whether a number is odd or even depends on divisibility by 2.

number MOD 2 = 0

number MOD 2

returns the remainder when

number

is divided by 2. If that remainder is zero, is the number odd or even?

number MOD 2 = 1

Correct!

number MOD 2

returns the remainder when

number

is divided by 2. If

number MOD 2

is 1, then the number is odd.

from Lab 4, Page 1

What's the value of 11 mod (2 + 3)

?

1

Correct!

0.2

Remainders are always whole numbers.

2

Mod gives you the remainder, not the quotient.

2.2

It's true that division and mod have some similarities, but mod gives you just the remainder.

from Lab 4, Page 3

When will "Error. Invalid entry." be displayed?

PROCEDURE greaterThanOrEqualTo(a, b)
    IF(a > b)
    {
        RETURN(true)
    }
    ELSE
    {
        RETURN(a = b)
    }
    DISPLAY("Error. Invalid entry.")
}

When

a > b

is true.

Think about what

RETURN

does. Like report in Snap!,

RETURN

ends the procedure. Once it is run, no other code in that procedure is run, and the flow of control returns to the place where the procedure was called.

When

a > b

is false.

Think about what

RETURN

does. Like report in Snap!,

RETURN

ends the procedure. Once it is run, no other code in that procedure is run, and the flow of control returns to the place where the procedure was called.

Always

It looks like that because that's the last line of procedure code, but think about what

RETURN

does. Like report in Snap!,

RETURN

ends the procedure. Once it is run, no other code in that procedure is run, and the flow of control returns to the place where the procedure was called.

Never

Correct!

from Lab 5, Page 1

IOC-1.F.2

Which of the following best describes a situation where intellectual property (IP) laws are violated?

Downloading a free application from the developer's website.

Downloading software legally from a developer’s website does not violate IP laws.

Sharing a movie file you purchased through a file-sharing service.

Correct! Sharing copyrighted content without authorization violates intellectual property laws.

Purchasing a song from an online music store.

Legally purchasing content does not violate IP laws.

Creating a backup copy of software you legally own.

Making a backup for personal use is generally legal under fair use or licensing terms.

from Lab 5, Page 2

IOC-1.F.5

Which statement incorrectly contrasts open access and open source?

Open access refers to online research output that is free of restrictions on access, while open source refers to software for which people can inspect the code.

This statement accurately defines both concepts.

Open source makes code available which may allow users to see how their data are being used, while open access refers to freely available research publications and data.

This statement accurately defines both concepts.

Open access applies to creative works, while open source applies to academic research.

Correct - this is an incorrect statement! Open access is for research, and open source applies to software, not academic research.

Open access is always free to read, while open source may have licensing terms that allow redistribution but restrict commercial use.

This statement accurately defines both concepts.

from Lab 5, Page 4

IOC-1.F.11

Imagine a new app called "StreamShare" has been developed, allowing users to download and share any digital media files, such as movies, music, and e-books. While the app is popular, critics have raised concerns about its impact on content creators and publishers. Which of the following is most likely the basis of their concern associated with apps like "StreamShare"?

The app may increase Internet traffic and the demand on Internet service providers.

While this could happen, it is not the primary legal concern with file-sharing.

The potential for copyright infringement.

Correct! File-sharing apps often raise concerns about unauthorized distribution of copyrighted content.

This popular app may compete with their file-sharing apps.

Competition is not the main legal concern.

This app may encourage sharing of inappropriate media content.

This could be a concern, but it is not the primary legal issue.

Lab 1: Games

Lab 2: Making Lists

Lab 3: Making Decisions

Lab 4: Making Computers Do Math

Lab 5: Copyrights