Computer Science Unit 2

What is the proper operator for "not equals" in JavaScript?

!=

What symbol represents the and operator in JavaScript?

&&

How can we check if a variable num is even?

(num % 2 == 0) will be true

What symbol do you use to do multiplication in JavaScript?

*

What symbol do you use to do division in JavaScript?

/

What is printed by the following program? function printNumbers(two, one, zero){ println(two); println(one); println(zero); } function start(){ var zero = 0; var one = 1; var two = 2; printNumbers(zero, one, two); }

0 1 2

How many return values come out of the function sum? function sum(first, second){ var result = first + second; return result; }

1

How many times will this program print "hello"? var i = 10; while (i > 0) { println("hello"); i--; }

10

What is the output of the following program? ar result = 0; var max = 5; for(var i = 0; i < max; i++){ result += i; } println(result);

10

What will be the value of sum after this code runs? var START = 1; var END = 4; function start(){ var sum = 0; for(var i = START; i <= END; i++){ sum += i; } }

10

What is the output of the following program? function start(){ var x = 5; sumTo(x); println(x); } function sumTo(num){ var sum = 0; for(var i = 0; i <= num; i++){ sum += i; } println(sum); }

15 5

What is printed when the following code is run? function doubleNumber(x){ return 2*x; } function start(){ var y = 4; var doubledY = doubleNumber(y); var result = doubleNumber(doubledY); print(result); }

16

In the following code, what will be the last number to print to the screen before the program finishes? for (var i = 0; i < 10; i++) { if (i % 2 == 0) { println(i); } else { println(2 * i); } }

18

How many parameters go into the function sum? function sum(first, second){ var result = first + second; return result; }

2

How many possible values can Randomizer.nextBoolean() return?

2

What is the last thing printed by the following program? var start = 30; var stop = 10; for(var i = start; i >= stop; i-=5){ if(i % 2 == 0){ println(i * 2); } else { println(i); } }

20

What is the output of the following code? function start(){ var x = 5; quadrupleNumber(x); } function quadrupleNumber(x){ var quadX = 4 * x; println(quadX); }

20

How many parameters go into the function sum, and how many return values come out of the function sum? function sum(first, second, third){ var result = first + second + third; println(first); println(second); println(third); return result; }

3 parameters go in, 1 return value comes out

How many times will the following code print "hello"? for (var i = 0; i < 8; i += 2) { println("hello"); }

4

What will the following code print to the screen? println(2 + 2);

4

What is printed by the following code? function printNumbers(first, second, third){ println(first); println(second); println(third); } function start(){ var middle = 5; printNumbers(4, middle, 6); }

4 5 6

How many times will the following code print "hello"? for (var i = 3; i < 8; i++) { println("hello"); }

5

How many times will the following program print "hello"? for (var i = 0; i < 5; i++) { println("hello"); }

5

What is printed by the following program? function product(x, y){ return x * y; } function difference(x, y){ return x - y; } function start(){ var x = 2; var y = 5; var value1 = product(x, y); var value2 = difference(y, x); var result = difference(value1, value2); println(result); }

7

What is the proper way to compare if two values are equal in a boolean expression in JavaScript?

==

The following code continually asks the user for a password until they guess the correct password, then ends. But there is one problem. 1 var SECRET_PASSWORD = "karel"; 2 3 function start(){ 4 while(true){ 5 var password = readLine("Enter your password: "); 6 if(password == SECRET_PASSWORD){ 7 println("You got it!"); 8 } 9 println("Incorrect password, please try again."); 10 } 11 }

Add a break; statement after line 7 so that the program doesn't loop infinitely

To ask the user of the program for a number, which function should you use?

Both readInt and readFloat are for numbers.

What is printed by the following program? var numApples = 10; var numOranges = 5; if(numApples < 20 || numOranges == numApples){ println("Hello, we are open!"); } else { println("Sorry, we are closed!"); } println("Sincerely, the grocery store");

Hello, we are open! Sincerely, the grocery store

What is printed by the following program? var isRaining = false; var isCloudy = false; var isSunny = !isRaining && !isCloudy; var isSummer = false; var isWarm = isSunny || isSummer; println("Is it warm: " + isWarm);

Is it warm: true

Why do we write functions?

Make our code easier to understand by giving a readable name to a group of instructions Avoid writing repeated code Make our code reusable All of the above

Which of the following returns a random number between 1 and 10?

Randomizer.nextInt(1, 10)

In the following code, we create a circle and add it to the screen. What is the meaning of the x variable? var x = 20; var circle = new Circle(x); add(circle);

The radius of the circle

In the following code: var size = 20; var x = 100; var y = 200; var ball = new Circle(size); ball.setPosition(x, y); What is the meaning of the x variable?

The x coordinate of the center of the circle

How many times will the following program print "hello"? var i = 0; while(i < 10){ println("hello"); }

This code will loop infinitely

How many times will this program print "hello"? var i = 50; while (i < 100) { println("hello"); }

This code will loop infinitely

Why do we use constant variables?

To avoid having "magic numbers" in our code To give values a readable name, so that their purpose is clear To let us easily change the behavior of our program by only having to change a value in one place All of the above

The following program should draw a circle on the screen 1 function start(){ 2 var circle = new Circle(40); 3 circle.setPosition(getWidth() / 2, getHeight() / 2); 4 circle.setColor(Color.blue); 5 } But when we run this code, we don't see the circle. What is missing from our start function?

We create the circle and position it correctly on the screen, but we never add it to the screen. We need to add the line add(circle); after line 4

What statement can we use inside of a loop to end it?

break

If we want to draw a circle using our helpful drawCircle function at position (300, 400) with a radius of 40 and color blue, which is the correct function call? As a reminder, here's the function header for drawCircle: function drawCircle(radius, color, x, y)

drawCircle(40, Color.blue, 300, 400);

What is the value of the boolean variable canVote at the end of this program? var age = 17; var isCitizen = true; var canVote = age >= 18 && isCitizen;

false

What are the parameters of the printNumbers function? function printNumbers(first, second, third){ println(first); println(second); println(third); }

first, second, third

We want to print the phrase "CodeHS is the best" exactly 25 times. What kind of control structure should we use?

for loop

"It's a bird! It's a plane! No, it's Superman!" We want to write a function isSuperman that takes in two parameters isBird and isPlane and returns true if it is in fact Superman, and false otherwise. If it's not a bird and it's not a plane, it must be Superman. Which of the following functions is the correct implementation of isSuperman?

function isSuperman(isBird, isPlane){ return !isBird && !isPlane; }

What function do you need to call to get the width of the screen?

getWidth()

What are the coordinates of the center of the window?

getWidth() / 2, getHeight() / 2

What are the coordinates of the top right corner of the screen?

getWidth(), 0

In a graphics canvas, what are the coordinates of the bottom right corner of the window?

getWidth(), getHeight()

What kind of statement allows us to run a block code only if a certain condition is true?

if statement

What kind of statement allows us to run one block of code if one condition is true, and a separate block of code otherwise?

if/else statement

What is the proper function to call to print to the screen?

println

What function do you need to call to ask the user of the program to enter text?

readLine

In the following code: var MAX_NUMBER = 10; function sum(x, y){ var result = x + y; //Point A return result; } function start(){ var num1 = Randomizer.nextInt(0, MAX_NUMBER); var num2 = Randomizer.nextInt(0, MAX_NUMBER); println( sum(num1, num2) ); } Which variables exist at point A? In other words, which variables are in scope at point A? Which variables could you type at point A and the program would still work?

result, x, y, and MAX_NUMBER

Which statement allows us to return values from functions?

return

What is the term for the value that signals the end of user input?

sentinel

After the following code runs, what is the value of isWeekend? var isSaturday = true; var isSunday = false; var isWeekend = isSaturday || isSunday;

true

What keyword do you need to use to define a variable in JavaScript?

var

Which of the following is a good example of a proper constant variable name?

var MAX_VALUE = 100;

You want to read input from the user to know how many apples they would like to buy. Which statement should you use to read in a number from the user?

var applesToBuy = readInt("How many apples would you like? ");

You are splitting up all of your apples equally between 3 people. Which statement below will calculate how many apples will be left over?

var leftOver = numApples % 3;

A store has 20 apples in its inventory. How can you store this information in a JavaScript variable?

var numApples = 20;

We want to position a Circle circle on our canvas to be at a random position, but we want to keep the entire shape on the screen. Which of the following will accomplish this?

var x = Randomizer.nextInt(circle.getRadius(), getWidth() - circle.getRadius()); var y = Randomizer.nextInt(circle.getRadius(), getHeight() - circle.getRadius()); circle.setPosition(x, y);

We want to simulate constantly flipping a coin until we get 3 heads in a row. What kind of loop should we use?

while loop

Which of the following is correct loop and a half structure?

while(true){ //code if(condition){ break; } //code }

In the following function printThreeTimes: function printThreeTimes(word){ println(word); println(word); println(word); } What is the parameter of the function?

word

function quadrupleNumber(x){ var quadX = 4 * x; println(quadX); } What is the parameter of the function quadrupleNumber?

x

In the following code snippet: function addTen(x){ var ten = 10; var result = x + ten; return result } function double(x){ var result = 2*x; return result; } What are the local variables of the function double?

x and result

Do functions need to have parameters?

yes

Which of the following is not a valid value for a boolean?

yes

What symbol represents the or operator in JavaScript?

||