AP Computer Science Principles

AP Computer Science Principles is organized around 5 big ideas, which provide a broad framework for the course. However, these big ideas can sometimes feel a bit vague when you’re trying to study effectively. To help you maximize your learning and build essential skills, I prefer breaking the class down according to the units in the Code.org curriculum. 

Below the unit breakdown, you’ll also find reviews tied back to the official AP big ideas to make sure you’re fully prepared. 

Big Idea 1: Creative Development

Quizlet Vocabulary: Big Idea 1 - Creative Development 

Big Idea 2: Data

Vocabulary: 

• Binary: A way of representing information using only two options.

• Bit: A contraction of "Binary Digit";  the single unit of information in a computer, typically represented as a 0 or 1

• Byte:  8 bits

• Overflow Error: Error from attempting to represent a number that is too large.

• Round-off Error: Error from attempting to represent a number that is too precise. The value is rounded.

• Analog Data: Data with values that change continuously, or smoothly, over time. Some examples of analog data include music, colors of a painting, or position of a sprinter during a race.

• Digital Data: Data that changes discretely through a finite set of possible values

• Sampling: A process for creating a digital representation of analog data by measuring the analog data at regular intervals called samples.

• Lossless Compression: A process for reducing the number of bits needed to represent something without losing any information. This process is reversible.

• Lossy Compression: A process for reducing the number of bits needed to represent something in which some information is lost or thrown away. This process is not reversible.

• Intellectual Property: A work or invention that is the result of creativity, such as a piece of writing or a design, to which one has rights and for which one may apply for a patent, copyright, trademark, etc.

• Creative Commons: A collection of public copyright licenses that enable the free distribution of an otherwise copyrighted work, used when an author wants to give people the right to share, use, and build upon a work that they have created

Big Idea 3: Algorithms and Programming

Make sure to familiarize yourself—and ideally even memorize—these common algorithms and code patterns. 

They’ll be incredibly helpful for the MCQ section, where questions often reference these exact snippets or structures directly.

Reasonable vs. Unreasonable Time is a tricky but important topic, and it’s guaranteed to show up on the AP Exam. Make sure to go through the doc below carefully to truly understand it.

Vocabulary:

Data Structures & Types

• Variable: abstraction inside a program that can hold a value.

• List: ordered sequence of elements.

• Element: individual value in a list that is assigned a unique index.

• Index: common method for referencing the elements in a list or string using natural numbers.

• String: ordered sequence of characters.

Operators

• Arithmetic operators: +, -, *, /, MOD.

• Boolean value: true or false.

• Relational operators: =, <, >.

• Logical operators: NOT, AND, OR.

Control Structures

• Selection: IF, ELSE, ELSE IF.

Procedures & Abstractions

• Procedure: group of programming instructions that may have parameters and return values.

• Parameters: input variables of a procedure.

• Arguments: specify the values of the parameters when a procedure is called.

• Procedural Abstraction: provides a name for a process and allows a procedure to be used only knowing what it does, not how it does it.

• Modularity: large problems are broken into subproblems.

• Library: contains procedures that may be used in creating new programs.

• Application Program Interfaces (API): specifications for how the procedures in a library behave & can be used.

Algorithms & Problem Solving

• Algorithm: finite set of instructions that accomplish a specific task.

• Stimulations: abstractions of more complex objects for a specific purpose.

• Problem: general description of a task.

• Decision problem: problem with a yes/no answer.

• Optimization problem: problem with the goal of finding the best solution.

• Efficiency: estimation of the amount of computational resources used by an algorithm (as a function of the size of the input).

• Reasonable Time: polynomial (linear, square, cube), or constant time.

• Unreasonable Time: exponential or factorial time → approximate solution needed.

• Heuristic: produces a solution that is not guaranteed to be optimal.

• Decidable Problem: an algorithm can be written to produce a correct output for all inputs.

• Undecidable Problem: no algorithm can be constructed that is always capable of providing a correct yes or no answer.

Big Idea 4 - Computer Systems and Networks

Vocabulary:

Hardware & Systems

• Computing device: physical artifact that can run a program

  • Examples: computers, tablets, servers, routers

• Computing system: a group of computing devices and programs working together for a common purpose

• Computer network: group of interconnected computing devices capable of sending or receiving data

• Internet: computer network consisting of interconnected networks that use standardized, open (nonproprietary) communication protocols

  • Scalability: capacity for a system to change in size and scale to meet new demands

  • Fault tolerant: system continues to function even if one or more components fail

  • Redundancy: inclusion of backup elements to ensure reliability

Networking Concepts

• Path: sequence of directly connected computing devices that begins at the sender and ends at the receiver

• Routing: process of finding a path from sender to receiver

• Bandwidth: maximum amount of data that can be sent in a fixed amount of time (measured in bits per second)

• Packets: chunk of data and metadata used for routing between origin and destination

  • May arrive in order, out of order, or not at all

Web Technologies

• World Wide Web: system of linked pages, programs, and files that uses the internet

  • HTTP: protocol used by the World Wide Web to transfer data

• Protocol: agreed-upon set of rules that specify the behavior of a system

  • IP (Internet Protocol)

  • TCP (Transmission Control Protocol)

  • UDP (User Datagram Protocol)

Computing Models

• Sequential computing: program runs one instruction after another, in order

• Parallel computing: program is broken into multiple smaller sequential computing operations

  • Allows tasks to be executed simultaneously

  • Efficiency is still limited by the sequential portion of the task

• Distributed computing: multiple devices are used to solve a much larger problem

• Speedup: a measure of efficiency

  • Formula: Speedup = Sequential Computing Time / Parallel Computing Time

Big Idea 5 - Impact of Computing

Unit 5 is pretty straightforward—no tricky concepts here! Just memorize the vocab terms, and you're golden.

Vocabulary:

Computing Innovations & Social Impact

• Computing Innovations: can be both harmful & helpful; effects may be anticipated or unanticipated

• Digital Divide: differing access to computing devices and the internet among groups of people

• Human Bias: biases in people can be reflected in computing innovations, including algorithms

• Citizen Science: scientific research conducted by distributed individuals who contribute data using their own computing devices

• Crowdsourcing: obtaining input, services, or content from a large number of people via the Internet

Intellectual Property & Access

• Intellectual Property: material created on a computer is the legal property of the creator or organization

• Creative Commons: public copyright license that allows sharing, using, and building upon a work

• Open Source: programs made freely available, and can be redistributed and modified

• Open Access: online research that is free of restrictions on both access and use

Data Privacy & Security

• Personally Identifiable Information (PII): information that identifies or links to an individual

  • Collected by search engines, websites, and devices

• Authentication: protects devices from unauthorized access

  • Methods: strong passwords, multifactor authentication (2+ steps)

• Encryption: process of encoding information

• Decryption: process of decoding encrypted information

Encryption Methods

• Symmetric Key Encryption: the same key is used for both encryption and decryption

• Public Key Encryption: uses a public key to encrypt and a private key to decrypt

  • The sender does not need the receiver’s private key to encrypt

  • The receiver's private key is required to decrypt

• Certificate Authorities: validate the ownership of encryption keys and ensure trust in secure connections

Cybersecurity Threats

• Computer Virus: malicious program that can copy itself and gain access to a computer

• Malware: software designed to damage or gain control of a computing system

• Phishing: deceptive attempts to trick users into providing personal or sensitive information

• Keylogging: secretly recording every keystroke made on a computer

• Rogue Access Point: unauthorized wireless access point that allows access to a secure network

The Ultimate Last-Minute AP CSP Guide

If you're reading this with less than 24 hours until your AP CSP exam and don't have time to review an entire year's worth of material, this is your lifeline. 

• Strategic MCQ approaches - proven techniques to tackle multiple choice questions

• Answer elimination strategies - systematic methods to narrow down options

• Essential concept refreshers - crucial topics that frequently trip students up

• High-yield review material - the most testable content, distilled

Born from the same pressure and urgency you're feeling right now, this guide was created during my own night-before-exam marathon study session. Sometimes the best resources come from necessity and adrenaline.

Instructions: Read through this guide completely, then cycle through it again. Focus on the sections that feel shakiest. 

Remember: Quality focused review beats quantity every time.

Create Task - Follow Rules

Don’t underestimate the Create Task. It’s not just a small part of the AP exam—it can be the difference between a 4 and a 5. 

🔍 Use the Best Resource:

The official AP Computer Science Principles Student Handouts PDF is your best friend. BEST! It clearly tells you exactly what to include. Read through it thoroughly, and when you start coding, reference it constantly to make sure you're meeting all the requirements.

✅ Key Tips for Success:

• Don’t use code you’re unsure about. If you can’t confidently explain what a section does, don’t include it.

• Don’t overcomplicate things. AP graders aren’t looking for complexity—they’re looking for clarity and whether you met the rubric.

• You WILL have to answer questions about your code on exam day. Keep everything clean, readable, and logical.

🧩 About the Personalized Project Reference:

This is the trickiest part for many students. You’ll need to take 4 screenshots of different code segments, each showing a required element:

1. A list used in your program.

2. A procedure you wrote, including:

   • A loop (for, while) → iteration

   • A conditional (if/else) → selection

   • A  parameter 

3. A call to your procedure (where it’s actually used).

4. A segment showing how your list impacts the program (its purpose/use in action).

👉 Plan ahead: When coding, think about how your code will break down into these segments. If you don’t, it’ll be a nightmare to screenshot later.

🧠 Common Pitfalls:

• “Can I include two segments in one screenshot?”
  Yes? No? I don't know. But here’s the rule: be clear. If there’s any doubt, revise your code to be simpler and clearer.

• Don’t rush submission. Never submit unless you are 100% confident in your final version (you cannot un-submit once you hit that button) 

  • Let it sit for a few days. Come back with fresh eyes—you’ll often spot things you didn’t notice before.

  • NEVER wait until the last minute.

🏁 Final Reminder:

This is meant to be a straightforward task, not a coding competition. The goal is to show you understand the fundamentals—not to impress with something overly complex.

If it checks every box on the rubric and is easy to explain—you’ve already won.

FRQ Section – Prepare Smart

You might be feeling nervous or unsure about what the FRQs will ask—especially because this has only being around for 2 years, with not much past examples to look at. But College Board has already given you the framework (see above pictures & link below) they use to write those questions. 

College Board Framework: https://apcentral.collegeboard.org/courses/ap-computer-science-principles/exam (scroll down to Exam Format section)

🧩 How the FRQs Work:

There are 2 main FRQ questions (the 2nd one with multiple subparts like a, b, c). Every single one of them is based on this framework—just customized a bit each year.

Why? Because your Create Task code will look different from everyone else's. So the questions have to be general enough to apply to any project, while still checking if you understand your own program.

💡 Game-Changing Tip:

If you want to know exactly what you need to say about your code on AP Exam day...

👉 Take your Create Task code + Personalized Project Reference + College Board Framework, and plug it into ChatGPT (or work through it yourself), let it go through each prompt from the framework and answer them based on your own code.

• Point out:

  • Which part is your iteration

  • Which part is your selection (if/else)

  • Where your list is created and used

  • Where you call your procedure

Read the responses carefully. Understand them. Try to rephrase them in your own words so you’ll be ready to explain your code on exam day—clearly and confidently.

🧠 Don’t Be Thrown Off by Weird FRQs… They Happen 😳

Yeah, sometimes College Board gets a little creative with their FRQ questions. It's not always going to be “What is the input of your program?”

Take 2024’s Set 1, Question 2 Part C for example (look it up if you are curious...)

💭 A List of Creative Questions (Just to Stretch Your Brain):

1.  Identify a group of users who weren’t your target audience. How might they interact differently with your program?
   Think about accessibility, age, social groups, etc.

2. Describe a situation where two different calls to the same procedure lead to a different number of iterations.
   (This was actually the FRQ in 2025 when I took the exam... and I predicted it ahead of time. YAY ME!! 🎉)

3. How would you test that a procedure works correctly without looking at its code?
   What arguments would you pass in? How would you know if it worked?

4. 📦 Could you rewrite your code to work without using a list?
   If yes, how? If not, what trade-offs would you face?

5. 💬 Explain how you used feedback, reflection, or testing during development.
   What helped you improve or debug?

6. 🔍 Consider your first if statement—can you rewrite its condition using a different (but equivalent) Boolean expression?
   This tests whether you actually understand logic and conditions.
   
   

You’ve been building your CS brain all year long. As long as you:

• Know your project

• Understand each element (list, loop, procedure, if/else)

• Practice explaining clearly

• Expect the unexpected...

You’ll be 100% ready.