Lecture 0 - Scratch

Question 1

What is the primary focus of computer programming?

Answer 1

Taking input and creating output to solve a problem

This process is often referred to as a black box where the internal workings are not visible.

Question 2

What counting system do computers use?

Answer 2

Binary

Binary uses digits 0 and 1.

Question 3

What is a bit?

Answer 3

A binary digit representing either a zero or one

A bit is the fundamental unit of data in computing.

Question 4

How many distinct values can three bits represent?

Answer 4

Eight

Three bits can represent values from 0 to 7.

Question 5

What is ASCII?

Answer 5

A standard that maps specific letters to specific numbers

ASCII uses binary patterns to represent characters.

Question 6

What is the mapping for the letter A in ASCII?

Answer 6

65

01000001 in binary represents the number 65.

Question 7

What does Unicode do?

Answer 7

Expands the number of bits to represent more characters and emojis

Unicode accommodates a wider range of characters than ASCII.

Question 8

What does RGB stand for?

Answer 8

Red, Green, Blue

RGB is a color model used to represent colors in digital images.

Question 9

What is an algorithm?

Answer 9

A step-by-step set of instructions to solve a problem

Algorithms can vary in efficiency and speed.

Question 10

What is big-O notation?

Answer 10

A way to describe the efficiency of an algorithm

It expresses how the time or space requirements grow relative to input size.

Question 11

What is pseudocode?

Answer 11

A human-readable version of code

Pseudocode helps in planning and understanding algorithms.

Question 12

What are conditionals in programming?

Answer 12

Statements that execute actions based on whether a specific condition is met

Commonly used in if-else structures.

Question 13

What is the purpose of abstraction in programming?

Answer 13

To simplify complex problems into smaller, manageable tasks

This helps in reducing complexity and improving code organization.

Question 14

What is Scratch?

Answer 14

A visual programming language developed by MIT

Scratch allows users to create programs without worrying about syntax.

Question 15

What is the first step to create a basic Scratch program?

Answer 15

Drag the ‘when green flag clicked’ block to the programming area

This starts the execution of the program.

Question 16

What is the output of the program where the cat says ‘hello, world’?

Answer 16

The cat says ‘hello, world’ when the green flag is clicked

This illustrates the input-output relationship in programming.

Question 17

What is a loop in programming?

Answer 17

A structure that repeats a block of code multiple times

Loops help in reducing repetition in code.

Question 18

What is the role of variables in programming?

Answer 18

To store data values that can change during program execution

Variables hold information that can be updated or referenced.

Question 19

What is an example of a simple conditional structure in Scratch?

Answer 19

if touching mouse-pointer? then play sound Meow

This checks a condition and executes an action based on it.

Question 20

What does the ‘forever’ block do in Scratch?

Answer 20

It continuously executes the code inside it

This is useful for ongoing checks or actions.

Question 21

What is the significance of CS50.ai?

Answer 21

An AI tool available for use during the course

It assists students without providing complete answers.

Question 22

What are conditionals in programming?

Answer 22

Conditionals are an essential building block of programming, where the program checks if a specific condition has been met and performs an action if it is.

Question 23

How does the forever block function in a conditional statement?

Answer 23

The forever block allows the if block to be triggered repeatedly, checking continuously if a condition is met.

Question 24

What is the purpose of the whenclickedforeveriftouchingmouse-pointer?thenplaysoundMeowuntildone code?

Answer 24

This code plays a sound continuously while the cat sprite is touching the mouse pointer.

Question 25

Fill in the blank: Oscartime is one of David’s own ______ programs.

Answer 25

[Scratch]

Question 26

What code is used to change Oscar's costume when the mouse is over him?

Answer 26

whenclickedswitchcostumetooscar1foreveriftouchingmouse-pointer?thenswitchcostumetooscar2elseswitchcostumetooscar1

Question 27

Describe how to create a falling piece of trash in Scratch.

Answer 27

Use the code: whenclickedgotox:pickrandom-240to240y:180foreverifdistancetofloor>0thenchangeyby-3.

Question 28

Fill in the blank: The code ______ allows for the possibility of dragging trash in Oscartime.

Answer 28

[whenclickedforeverifmousedown?andtouchingmouse-pointer?thengotomouse-pointer]

Question 29

How do you implement scoring in Oscartime?

Answer 29

Use the code: whenclickedforeveriftouchingOscar?thenchangescoreby1gotox:pickrandom-240to240y:180.

Question 30

What are the three main components of Ivy’s Hardest Game?

Answer 30

1. Initial position and keyboard listening 2. Movement controls for arrow keys 3. Wall detection for safe positioning.

Question 31

What does the code definefeelforwalls do?

Answer 31

It checks if the sprite is touching a wall and moves it back to prevent it from walking off the screen.

Question 32

True or False: Scratch allows multiple sprites to be on the screen at once.

Answer 32

True.

Question 33

What code allows a sprite to follow another sprite in Ivy’s Hardest Game?

Answer 33

whenclickedgotorandom positionforeverpointtowardsHarvardmove1steps.

Question 34

What fundamental programming skill is introduced in this course?

Answer 34

Pseudocoding.

Question 35

List the basic building blocks of programming covered in this course.

Answer 35

* Functions * Conditionals * Loops * Variables.

Question 36

What is the essence of the work of computer scientists?

Answer 36

Problem-solving.

Question 37

Fill in the blank: This course will introduce you to a new way of learning that you can apply to almost every area of ______.

Answer 37

[life]

Question 38

How are numbers, text, images, music, and video represented by computers?

Answer 38

They are understood and represented through various programming constructs and data types.

Question 39

What should you do if you get frustrated while programming?

Answer 39

Take time to talk yourself through the problem and identify what is working and what is not.