The Stacks
AP COMPUTER SCIENCE

AP Computer Science Principles

Everything on the AP CSP exam, organized exactly the way the College Board's Course and Exam Description (CED) organizes it: five Big Ideas, 35 numbered topics. Each topic page has the essential knowledge, a worked example, an exam tip, practice questions in the real exam's style, and the vocabulary you'll be tested on.

The 5 Big Ideas

Weight shown is that big idea's share of the multiple-choice exam.

How the exam works

  • Section I — End-of-course multiple choice. 70 questions, 120 minutes, 70% of your score. Every question has 4 options. Most are single-select; a handful are multi-select where you must pick two correct answers to get credit.
  • Section II — Create Performance Task. 30% of your score. You build a program during the year (at least 12 hours of class time), submit the code and a video, then answer written-response prompts about it on exam day.
  • There is no penalty for guessing on multiple choice — answer every question.
  • All code on the exam is in AP pseudocode (text-based and block-based). A reference sheet is provided, but you're expected to read it fluently, not learn it during the test.
  • Roughly 25% of questions are code-analysis: given a snippet, predict output, find the bug, or pick the equivalent code. Practice tracing by hand, line by line, with a table of variable values.

What separates a 5 from a 3

  • Trace code with a variable table. The most common lost points are careless tracing errors in Big Idea 3 — writing each variable's value after every line catches them.
  • Know the exam's vocabulary precisely. Lossy vs. lossless, procedural vs. data abstraction, parallel vs. distributed, sequential vs. selection vs. iteration — many questions are essentially "which term describes this scenario."
  • Weigh both sides in Big Idea 5. Impact questions reward answers that acknowledge an innovation can be beneficial for one group and harmful for another; extreme, one-sided options are usually wrong.
  • Read the whole stem. Distractors are built from a partial reading. Underline what is actually being asked (output? number of iterations? which change preserves behavior?).
  • Spend proportionally. Big Idea 3 (30–35%) and Big Idea 5 (21–26%) are over half the multiple choice. Study time should mirror that.

Practice tracing

Interactive, step-by-step walkthroughs of the loops, lists, and recursion the exam asks you to trace by hand.

▶Code tracerinteractive