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CSA · Progress Checks

AP Computer Science A Progress Check walkthroughs.

Unit-by-unit explanations of the MCQ and FRQ content on AP Classroom Progress Checks. Each unit page shows the topics tested, the most common student mistakes, and a tip from someone who scored a 5.

Updated July 2025 Written by Mahmudul Hasan Free · No signup
10 units

All units, expandable.

Click a unit to see MCQ topics, FRQ structure, common mistakes, and a tip from a student who scored a 5.

U01Primitive Types12 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Variables
  • Casting
  • Operators
FRQ guidance
  • Output prediction
Common mistake
Integer division dropping the decimal.
Tip from a 5-scorer
5 / 2 in Java = 2, not 2.5. Cast to double first.
U02Using Objects16 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Classes vs. objects
  • Methods
  • String
FRQ guidance
  • Method tracing
Common mistake
Confusing == with .equals() on Strings.
Tip from a 5-scorer
== checks reference. .equals() checks content.
U03Boolean Expressions and If16 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Conditionals
  • De Morgan
  • Short-circuit
FRQ guidance
  • Conditional logic
Common mistake
Forgetting short-circuit evaluation.
Tip from a 5-scorer
&& stops on first false. || stops on first true.
U04Iteration20 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • for
  • while
  • Nested loops
FRQ guidance
  • Loop tracing
Common mistake
Off-by-one errors in for loops.
Tip from a 5-scorer
for (int i = 0; i < n; i++) iterates n times — not n+1.
U05Writing Classes22 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Constructors
  • Methods
  • Encapsulation
FRQ guidance
  • Class design FRQ
Common mistake
Forgetting to initialize instance variables.
Tip from a 5-scorer
Constructor MUST set every instance variable or accept defaults.
U06Array18 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Single arrays
  • Traversals
  • Search
FRQ guidance
  • Array manipulation
Common mistake
Going out of bounds: array[length] doesn’t exist.
Tip from a 5-scorer
Indices are 0 to length−1.
U07ArrayList16 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • ArrayList
  • Methods
  • Resizable
FRQ guidance
  • ArrayList traversal
Common mistake
Modifying ArrayList while iterating with for-each.
Tip from a 5-scorer
Use index-based loop when removing. for-each crashes.
U082D Array12 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • 2D arrays
  • Row/col traversal
FRQ guidance
  • Matrix problems
Common mistake
Confusing row vs. column index order: array[row][col].
Tip from a 5-scorer
Outer loop = row. Inner loop = column. Mnemonic: “R before C.”
U09Inheritance18 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Polymorphism
  • Overriding
  • super
FRQ guidance
  • Inheritance hierarchy FRQ
Common mistake
Calling overridden method from constructor.
Tip from a 5-scorer
Polymorphism in constructors can call subclass overrides — fragile.
U10Recursion12 questions covered · MCQ + FRQ walkthroughs
MCQ guidance
  • Base case
  • Recursive case
  • Trace
FRQ guidance
  • Recursion trace
Common mistake
Forgetting the base case.
Tip from a 5-scorer
Always write the base case FIRST. Then the recursive call.
Make it count

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Practice loop
Do a Progress Check. Score yourself. Adjust.

After each unit, plug your AP Classroom score breakdown into the calculator. You’ll see your trajectory in real numbers, not vibes.

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Frequently asked questions

Quick answers — written by humans, not a chatbot.

What's the difference between CSA Progress Checks and the real AP exam?

Progress Checks are unscaled — they’re unit-by-unit MCQ + FRQ practice that AP Classroom assigns. The real AP exam uses a curve to map your raw composite to a 1–5. The walkthroughs above explain the reasoning; the calculator estimates your exam score.

Should I do every Progress Check or skip around?

Do them in order the first time — each one builds on the last. If you’re reviewing in May, target the units where you’re weakest using the unit summaries above.

Why don't you publish exact answer keys?

AP Classroom assignments are graded as your own work. Posting raw keys would help cheaters and harm the students using Curve for actual studying. Our walkthroughs explain reasoning, not letter answers.

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