AP Computer Science Principles Study Guide

Unit 1: The Internet

Lesson 1: Personal Innovations

• Innovation: A new or improved idea, device, or product.
• Computer Science impacts various fields like energy, fashion, and medicine.

Lesson 2: Sending Binary Messages

• Binary: A number system using only 1 and 0.
• Bit: Short for "binary digit," the single unit of information in a computer.
• Binary questions have two answers (e.g., Yes/No).

Lesson 3: Sending Binary Messages with the Internet Simulator

• Bandwidth: Transmission capacity measured by bit rate.
• Bit rate: Number of bits conveyed or processed per unit of time (e.g., 8 bits/sec).
• Latency: Time for a bit to travel from sender to receiver.
• Protocol: Rules directing data transmission between devices.
• Internet: A physical system for moving information using wires, cables, and Wi-Fi.
• Internet delivers information in bits, similar to a postal system.
• 8 bits = 1 byte, 1024 bytes = 1 kilobyte, 1024 kilobytes = 1 megabyte.
• Methods to send bits: Electricity, Light and Radio.
• Bandwidth increases the number of bits sent per second.

Lesson 4: Number Systems

• Number systems rely on place patterns and rules for accuracy.

Lesson 5: Binary Numbers

• The binary number system uses only 0s and 1s.

Lesson 6: Sending Numbers

• Protocol: Rules governing data exchange between devices.

Lesson 7: Sending Text

• Abstraction: A simplified representation of complexity.
• ASCII: American Standard Code for Information Interchange.
• Protocol: Rules governing data exchange between devices.

Lesson 8: The Internet

• IETF: Internet Engineering Task Force, develops Internet standards and protocols (TCP/IP).
• Internet: A computer network providing information and communication services.
• Net Neutrality: All Internet traffic should be treated equally by ISPs.
• The Internet is composed of independently operated networks.

Lesson 9: The Need for Addressing

• IP Address: A number assigned to any item connected to the Internet.
• Packet: A small block of information sent over a network.
• Protocol: Rules governing data exchange between devices.
• IP Addresses & DNS
  • Internetworking protocol created by Vint Cerf and Bob Kahn.
  • IP (Internet Protocol) Address.
  • Traditional IP addresses are 32 bits long.
    • IPv4 has 4 billion unique addresses.
  • IPv6 is advanced with 340 undecillion unique IP Addresses.
  • DNS associates website names with IP addresses.
• 2^6 = 64 unique IP addresses can be made in a fixed length IP address system using 6 bits.

Lesson 10: Routers and Redundancy

• Network Redundancy: Multiple backups to ensure reliability.
• Router: A computer that forwards data across a network.
• Packets may be rerouted many times.
• A packet contains addressing information for routing.

Lesson 11: Packets and Making a Reliable Internet

• Packets: Small chunks of information.
• TCP: Transmission Control Protocol, provides reliable, ordered, error-checked delivery of packets.
• Information travels in packets that take various routes.
• Routers manage packet flow efficiently.
• TCP manages sending and receiving data to ensure delivery.
• Fault tolerant: not many errors since there are many paths (Reliability)

Lesson 12: The Need for DNS

• DNS: Domain Name System, translates domain names to IP addresses.

Lesson 13: HTTP and Abstraction

• DNS: Translates domain names to IP addresses.
• HTTP: HyperText Transfer Protocol, transmits web pages.
• URL: Easy-to-remember address for a web page.
• HTTP requests use abstractions provided by lower-level protocols.
• Displaying a webpage requires multiple HTTP requests.

Unit 2: Digital Information

Lesson 1: Bytes and File Sizes

• 1 photo is about 2-5 megabytes.

Lesson 2: Text Compression

• Heuristic: A problem-solving approach to find a satisfactory solution.
• Lossless Compression: Allows original data to be perfectly reconstructed.
• Lossy Compression: Discards some data using approximations (e.g., .jpg).

Lesson 3: Encoding B&W Images

• Image: Data for graphics or pictures.

Lesson 4: Encoding Color Images

• Pixel: Short for "picture element", the fundamental unit of a digital image.
• RGB: Color model using intensities of Red, Green, and Blue.
• Hexadecimal: A base-16 number system (0-9 and A-F).

Lesson 5: Lossy vs Lossless Compression

• Lossless Compression: Allows perfect reconstruction of original data.
• Lossy Compression: Uses approximations, discarding some data.
• Metadata: Data that describes other data.

Abstraction

• Abstraction reduces detail to focus on relevant concepts.

Algorithm

• Algorithm: is a precise sequence of instructions for a process that can be executed by a computer.

Unit 3: Intro to Programming

Lesson 1: The Need for Programming Languages

Lesson 2: The Need for Algorithms

• Algorithm: A list of steps to finish a task.
• High Level Programming Language: A programming language with many commands and features designed to make common tasks easier to program.
• Low Level Programming Language: A programming language that captures only the most primitive operations available to a machine.

Lesson 3: Creativity in Algorithms

• Algorithm: A list of steps to finish a task.
• Iterate: Repeat to achieve a goal.
• Selection: An if-statement that uses a Boolean condition to determine.
• Pair Programming: Two programmers write code using a single computer.

Lesson 4: Using Simple Commands

• Turtle Programming: commands to control movement and drawing of an on-screen robot called a "turtle".

Lesson 5: Creating Functions

• Abstraction: Hiding details to manage complexity.
• Function: A named bit of programming instructions.
• Steps to creating functions in JavaScript
  • Defined the function (give a single name to represent the set of actions)
  • Call it (type the name of the function followed by a parentheses)
• Defining a function:
  • function [function name] () {
  • [write commands/steps] }
• Calling a function:
  • [function name] ();
• Generic term is procedure.
• Give functions meaningful names.

Lesson 6: Functions and Top-Down Design

• Abstraction: A simplified representation of something more complex.
• Function: A named bit of programming instructions.
• Top-Down Design: Break a system to gain insight into the subsystems that make it up

Lesson 7: APIs and Function Parameters

Lesson 8: APIs and Function Parameters

• API: Application Program Interface, a collection of available commands.
• Documentation: Description of a command's behavior.
• Library: Commands/functions with a shared purpose.
• Parameter: Extra information passed to a function to customize it.
• Generalized behavior of repetition per function can be represented with the parameter.
• Parameters help generalize the solution.

Lesson 9: Looping and Random Numbers

• For Loop: Loops that have a predetermined beginning, end, and increment (step interval).
• Loop: Repeating an action.

Unit 4: Big Data and Privacy

Lesson 1: What is Big Data?

• Big Data: Datasets too large or complex for traditional processing.

Lesson 2: Finding Trends with Visualization

Lesson 3: Check your assumptions

Lesson 4: Rapid Research- Data Innovations

• Code is used in medicine.
• Everyone has a sequence of DNA, this is how we can identify any viruses or diseases visible in a person’s DNA

Lesson 5: Identifying People with Data

• Computing Innovation: A program using code as an essential part of its functionality.

Lesson 6: The Cost of Free

Lesson 7: Simple Encryption

• Caesar Cipher: Shifts the alphabet by a certain number of characters for encryption.
• Cipher: A technique that performs encryption.
• Cracking encryption: Attempting to decode a secret message without knowing the cipher details.
• Decryption: Reversing encryption.
• Encryption: Encoding messages to keep them secret.
• Random Substitution Cipher: Maps each letter to a randomly chosen letter.

Lesson 8: Encryption with Keys and Passwords

• Computationally Hard: A problem a computer can't solve in a reasonable time.
• Encryption: Hiding a message.
• Decryption: Unscrambling a message.
• Caesar cipher Associates each number in the alphabet with a certain Number of steps below or above a certain letter.

Lesson 9: Public Key Crypto

• Symmetric encryption: the same key used to encrypt and decrypt.
• Asymmetric encryption: Different keys for encrypting and decrypting
  • Public key: shared with everybody so anybody can encrypt a message.
  • Private key: can only be decrypted by a computer with access.

Lesson 10: Rapid Research- Cybercrime

• Antivirus Software: usually keeps big lists of known viruses and scans your computer looking for the virus programs in order to get rid of them.
• DDoS Attack: Distributed Denial of Service Attack
• Firewall - software that runs on servers (often routers) that only allows traffic through according to some set of security rules.
• Phishing Scam - a thief trying to trick you into sending them sensitive information
• SSL/TLS: Secure Sockets layer/ Transport Layer Security
• Cybercrime exploits vulnerabilities and causes problems for families, society, financially, and with national security.

Unit 5: Building Apps

Chapter 1: Event-Driven Programming

Lesson 1: Buttons and Events

• Callback function: Function called by the system after an event.
• Event: An action that causes something to happen.
• Event-driven program: Program that runs code in response to events.
• Event handling: Coding tasks to make a program respond to events.
• Event listener: Command triggering a function upon an event.
• UI Elements: On-screen objects like buttons and images.
• User Interface: Visual elements for user control.

Lesson 2: Multi-Screen apps

• setScreen (screenId) is used to set a screen to a particular one of the screens in the app

Lesson 3: Building an App: Multi-Screen App

Lesson 4: Controlling Memory with Variables

• Debugging: Finding and fixing program problems.
• Data Type: A single value of either TRUE or FALSE
• Expression: Any code that resolves to a value

Lesson 5: Build an App: Clicker Game

• = = - The equality operator is used to compare two values and returns a Boolean.
• Global Variable - A variable whose scope is "global" to the program

Lesson 6: User Input and Strings

• setText(id,text) sets the text for the specified screen element.
• If-Statement - The common programming structure that implements "conditional statements".
• Local Variable - A variable with local scope is one that can only be seen, used and updated by code within the same scope.
• Concatenate - to link together
• String - Any sequence of characters between quotation marks

Lesson 7: "If" Statements Unplugged

• setText(id,text) sets the text for the specified screen element.

Lesson 8: Boolean Expressions and “If” Statements

• Boolean - A single value of either TRUE or FALSE
• Boolean Expression - in programming, an expression that evaluates to True or False.

Lesson 9: "if-else-if" and Conditional Logic

• Boolean - A single value of either TRUE or FALSE
• Boolean Expression - in programming, an expression that evaluates to True or False.

Chapter 2: Programming with Data Structures

Lesson 10: Building an App: Color Sleuth

Lesson 11: While Loops

Lesson 12: Loops and Simulations

• Iterate - To repeat in order to achieve, or get closer to, a desired goal.
• while loop - a programming construct used to repeat a set of commands (loop) as long as (while) a boolean condition is true.

Lesson 13: Introduction to Arrays

• Array - A data structure in JavaScript used to represent a list.
• List - A generic term for a programming data structure that holds multiple items.

Lesson 14: Building an App: Image Scroller

Lesson 15: Processing Arrays

• for loop - A typical looping construct designed to make it easy to repeat a section of code using a counter variable.

Lesson 16: Functions with Return Values

• Return Value - A value sent back by a function to the place in the code where the function was called from

Lesson 17: Building an App: Canvas Painter