AP Computer Science Principles Cheatsheet 2024

Computing Innovation

• Definition: Innovation using a program as a key function.
• Examples:
  • Physical: Robots, tablets, smart tech.
  • Non-physical: Social media, video games.

Collaboration

• Benefits: Diverse ideas catering to different people.
• Pair Programming: Two people sharing one computer and taking turns coding.

Program Function and Purpose

• Purpose: What a program is designed to do (e.g., solving problems, creative expression).
• Code Segments: Smaller collections of statements within a program.
• Code Statements: Individual instructions.
• Program Inputs: Data a computer takes in and processes (visual, auditory, touch, etc.).
• Program Outputs: Data the computer returns (same types as inputs).
• Program Events: Actions that give a program data to respond to.
• Program Behavior: How a program responds to user interaction.

Development Processes

• Iterative Development: Developing working prototypes and redeveloping the program through cycles.
• Incremental Development: Breaking a problem into small parts and reassembling the solution when each part is fixed.
• Program Documentation: Description of how something in the program works.
• Comments: Program documentation written directly into the program itself.

Common Errors

• Logic Errors: Unexpected behavior in program’s output.
• Syntax Errors: Code does not work properly due to incorrect typing or writing.
• Run-Time Errors: Error occurs while the code runs.
• Overflow Errors: Numbers are too big for the computer.

Methods of Fixing Errors

• Hand Tracing: Manually tracking variables' values as the program goes along.
• Print Statements: Printing out values to ensure they’re correct.

Data

• Definition: A collection of facts.
• Storage: Computing devices store data in bits (binary digits).
• Machine Code: Computers read machine code, usually in binary.
• Abstraction: Reduces complexity by focusing on the most important parts and hiding irrelevant parts from the user.

Binary Numbers

• 8 bits = 1 byte
• Hexadecimal: Used for RGB color codes; uses Base 16.

Data Representation

• ASCII code: Converts text to binary format.
• Analog Data: Measured continuously and changes smoothly.
• Digital Data: Measured digitally, simplifying data collected (form of abstraction).

Data Compression

• Dependent on the method used and the amount of repeated info in the data.
• Lossless Compression: Less compression and better file quality.
• Lossy Compression: More compression and worse file quality.

Extracting Information from Data

• Metadata: Data about data.
• Data Mining: Examining very large data sets to find information.
• Transforming Data: Editing or modifying data (e.g., doubling every number, graphing data points).
• Cleaning Data: Making data uniform without changing meaning (e.g., correcting misspelled words).

Pseudocode

• Important for the MCQ section of the AP Exam.
• AP Pseudocode has an index that starts at 1.

Data Types

• Examples: Numbers, strings, lists, and booleans.
• Strings: Ordered list of characters (“hello world”).
• Substrings: Part of a string (“ello”).
• String Concatenation: Connecting two or more strings with a “+”.
• List (Array): Ordered sequence of elements.
• Element: Individual value in a list.
• Index: Number representing the position in the list (e.g., in the list [5,6,7], 5 is at index number 1).
• Booleans: Either True or False; used with logical operators (NOT, AND, OR).

Mathematical Operators

• Refer to the exam reference sheet for the meaning of operators such as / and %.
• MOD (%) gives the remainder of 2 numbers.

Algorithms

• Definition: Instructions that accomplish a task or solve a problem; created using sequencing, selection, and iteration.

Sequencing, Selection, and Iteration

• Sequencing: Code executed in the order it is written.
• Selection: If statements with conditions that need to be met for the selection to run.
• Else Statements: Attached to if statements, specifying what happens if a condition is not met.
• Nested Conditional Statements: Conditional statements inside of conditional statements.
• Iteration: “repeat n times”/”repeat until”; using NOT, AND, and OR to write loops.
• Binary Search: Algorithm used to search; works by splitting the data set and eliminates ½ the data with each round of splitting.

Procedures/Functions

• Definition: Programming instructions also called methods or functions.
• Parameters: Input variables of a procedure.
• Arguments: A procedure call with defined values.
• Abstraction: Calling a procedure without knowing how it works.

The Internet

• Definition: Interconnection of networks.
• Computer Network: Multiple computing devices (e.g., computer, tablet) communicating with each other.
• Data Packets: Data on the internet is split into data packets with metadata attached to each packet to tell the routers information.
• Routing: The process of finding the best path to deliver information.
• Path: Sequences of connected computing devices (routers) that begin at the sender and end at the receiver.
• Bandwidth: The rate of data transfer from one device to another; megabits per second.
• Protocol: Set of rules; the internet uses the TCP/IP and UDP protocols to communicate.
• World Wide Web: A system of web-pages, programs, and files; runs on the Internet but is not the internet.
• Scalability: The capacity to change in size and scale to meet new demands.

Fault Tolerance

• Fault Tolerant: Something can still function even with a partial malfunction.
• Redundancy: Duplication of things; helps make the internet fault tolerant.

Parallel and Distributed Computing

• Sequential Computing: Traditional programming where each program is processed at a time.
• Parallel Computing: Program broken into smaller operations and processed at the same time using multiple processors.
• Distributed Computing: Multiple devices communicate together to run a program.
• Sequential Solution: Takes as long as the # of all steps in a program;
  • With 3 steps of a, b, and c length, the sequential solution equals a + b + c
• Parallel Computing Solution: Faster with less # of cores; if all steps are independent, find the solution that results in the minimum possible time.
• Speedup of a Parallel Solution: \frac{Sequential Solution Time}{Parallel Solution Time}

Key Concepts

• Digital Divide: Gaps between those who have access to the internet and those who do not.
  • Affected by demographics, socioeconomic status, and geographic location.
• Computing Bias: Computing innovations can reflect existing racial/gender/etc biases.
  • Often because computers run on historical data, which reflects historical biases.
• Intellectual Property: The work that people consider “theirs”.
• Copyright: The person who created something determines who uses their creation.
• Creative Commons: Copyright license for creators to give others the ability to use their work.
• Open-Sourcing: Work is freely shared, distributed, and modified.
• Open Access: Research available to the public without restrictions.
• Crowdsourcing: Getting a large amount of input or information from people on the Internet.
• Citizen Science: Scientific research that the general population helps to conduct.

Digital Security

• Personally Identifiable Information (PII): Information that can be used to identify you.
• Virus vs Worm: Viruses are attached to infected files and must be activated by the user; worms can operate independently.
• Malware: Malicious software that takes control of a system.
• Phishing: Tricks people into giving their personal information away by pretending to be a trustworthy group.
• Multi-Factor Authentication: Requiring multiple methods of verification.

Encryption

• Definition: Encoding data to prevent others from accessing it.
• Key: A secret piece of information used to encrypt data.
• Symmetric Key Encryption: One key for both encrypting & decrypting.
• Public Key Encryption: Public key to encrypt & private key to decrypt.

MCQs Exam Tips

• 120 minutes (2 hrs) | 70 multiple choice questions | 70% of AP Exam Score
  • Pace yourself! You have around 1.7 minutes for each question so make sure to keep track of the time.
  • If you are confused on a question, skip and come back later. If you cannot understand a question within 5-10 seconds of reading it, try to answer other questions first.
  • If necessary, guess. College Board does not have a guessing penalty (points are only rewarded if earned, not taken away if answered incorrectly.
  • Read the AP CSP reference sheet ahead of time for easy use on the AP Exam.
  • Find and use practice questions! Practice makes perfect!

Performance Task Exam Tips

• 9 hours in class work time | 30% of AP Exam Score
  • Work ahead of time! Try to avoid submitting your Create Task late to avoid technical errors.
  • Before submitting, review the scoring guidelines on the College Board website to make sure you have fulfilled the requirements for each row on the rubric.
  • To make sure your Create Task is completed properly, view the sample responses on the College Board
    Website and cross reference and compare your work to the samples.
  • Any examples or samples you see, write down to make sure you do not accidentally plagiarize. A Create Task that is flagged for plagiarism will receive a score of 0.
  • Be confident in your work! You have gone through this class for an entire year & are prepared!