AP Computer Science Principles Final
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Key Practice Questions and Verified
Detailed Answers; for Guaranteed Success
This AP Computer Science Principles (CSP) exam consists of a 50-question multiple-choice,
T/F& short answers, Create Performance Task (worth 30% of the score), focusing on five big
ideas: Creative Development, Data, Algorithms/Programming, Computer Systems/Networks,
and Social Impacts. The exam covers 70% of the final score,
Exam Structure & Components
• Create Performance Task (30% of score): Students develop a program, submit
code, a video, and written responses, with at least 9 hours of class time provided.
Key Content Areas (Big Ideas)
1. Creative Development: Collaboration, design process, and program documentation.
2. Data: Binary, data compression, data analysis, and extraction.
3. Algorithms and Programming: Variables, lists, loops, procedures, and logic.
4. Computer Systems and Networks: Internet protocols, routing, and cybersecurity.
5. Impacts of Computing: Digital divide, crowdsourcing, and ethical issues.
Q1. Public key encryption uses pairs of keys: a public key that can be distributed
widely and a private key that is known only to the owner. [True/False]
A) True
B) False
Answer: True
Explanation: Public key (asymmetric) cryptography uses a pair of keys: a public key that can be
shared widely and a private key kept secret. The public key can be used to encrypt messages for
the private key holder or to verify signatures, while the private key is used to decrypt or sign,
enabling secure communication without prior secret sharing.
,Q2. Moore's Law states that the number of transistors on a chip doubles every
year. [True/False]
A) True
B) False
Answer: False
Explanation: Moore's Law is the empirical observation that the number of transistors on an
integrated circuit doubles roughly every two years, not every year. Saying it doubles every year
overstates the historical rate.
Q3. An undecidable problem is one for which it is impossible to create an
algorithm that answers yes or no correctly for every possible input. [True/False]
A) True
B) False
Answer: True
Explanation: An undecidable problem is one for which no single algorithm can correctly answer
yes/no for every possible input; there is provably no algorithm that solves all instances. The
canonical example is the halting problem: no algorithm can decide for every program/input pair
whether the program halts.
Q4. Lossy compression discards some original data and typically makes it
impossible to fully recover the exact original, allowing greater size reduction (for
example, JPEG). [True/False]
A) True
B) False
Answer: True
Explanation: Lossy compression deliberately discards some information to reduce size; because
that information is removed, the original cannot be exactly reconstructed. Lossy methods
generally achieve higher compression ratios and are used when perfect fidelity is not required
(e.g., JPEG for photos).
Q5. Lossless compression preserves all original data and allows full recovery of
the original, though it usually achieves less compression than lossy methods (for
example, PNG). [True/False]
A) True
, B) False
Answer: True
Explanation: Lossless compression reduces data size while preserving all original information so
the exact original can be reconstructed. Because no data is thrown away, lossless methods
usually compress less than lossy ones (PNG is a common lossless image format).
Q6. Explain what lossy compression is and why it can produce higher
compression ratios; refer to the example in the text. [Short Answer]
Answer: Lossy compression intentionally discards some original data to achieve much
smaller file sizes, which prevents perfect recovery of the original—JPEG images are a
common example where detail is thrown away for greater compression.
Explanation: Lossy methods trade fidelity for size by removing information deemed less
important, so they compress more effectively than lossless approaches. A complete answer states
that data is thrown away, notes the irreversible nature of the process, and cites JPEG as the
illustrative example provided.
Q7. Explain what round-off error is and how limited bit precision leads to it,
using the π example from the text. [Short Answer]
Answer: Round-off error occurs when there aren't enough bits to represent a number
exactly, so the value is approximated (for example, storing π with three digits as 3.14),
producing small differences from the true value.
Explanation: Limited precision means some real numbers cannot be stored exactly; rounding or
truncation produces a nearby representable value. A complete answer names limited bit
precision as the cause, describes approximation (rounding), and uses the π example to show how
digits are cut off.
Q8. Which scenario best exemplifies an overflow error in a digital system?
[Multiple Choice]
A) A car odometer rolls from 99999 to 00000 because the bits available can't represent
the larger value
B) A program records π as 3.14 because only a few digits are stored
C) An image saved as JPEG looks slightly degraded after compression
D) A photo file lists aperture, GPS coordinates, and timestamp
Answer: A car odometer rolls from 99999 to 00000 because the bits available can't
represent the larger value
Exam Review | Expert Strategies, Review of
Key Practice Questions and Verified
Detailed Answers; for Guaranteed Success
This AP Computer Science Principles (CSP) exam consists of a 50-question multiple-choice,
T/F& short answers, Create Performance Task (worth 30% of the score), focusing on five big
ideas: Creative Development, Data, Algorithms/Programming, Computer Systems/Networks,
and Social Impacts. The exam covers 70% of the final score,
Exam Structure & Components
• Create Performance Task (30% of score): Students develop a program, submit
code, a video, and written responses, with at least 9 hours of class time provided.
Key Content Areas (Big Ideas)
1. Creative Development: Collaboration, design process, and program documentation.
2. Data: Binary, data compression, data analysis, and extraction.
3. Algorithms and Programming: Variables, lists, loops, procedures, and logic.
4. Computer Systems and Networks: Internet protocols, routing, and cybersecurity.
5. Impacts of Computing: Digital divide, crowdsourcing, and ethical issues.
Q1. Public key encryption uses pairs of keys: a public key that can be distributed
widely and a private key that is known only to the owner. [True/False]
A) True
B) False
Answer: True
Explanation: Public key (asymmetric) cryptography uses a pair of keys: a public key that can be
shared widely and a private key kept secret. The public key can be used to encrypt messages for
the private key holder or to verify signatures, while the private key is used to decrypt or sign,
enabling secure communication without prior secret sharing.
,Q2. Moore's Law states that the number of transistors on a chip doubles every
year. [True/False]
A) True
B) False
Answer: False
Explanation: Moore's Law is the empirical observation that the number of transistors on an
integrated circuit doubles roughly every two years, not every year. Saying it doubles every year
overstates the historical rate.
Q3. An undecidable problem is one for which it is impossible to create an
algorithm that answers yes or no correctly for every possible input. [True/False]
A) True
B) False
Answer: True
Explanation: An undecidable problem is one for which no single algorithm can correctly answer
yes/no for every possible input; there is provably no algorithm that solves all instances. The
canonical example is the halting problem: no algorithm can decide for every program/input pair
whether the program halts.
Q4. Lossy compression discards some original data and typically makes it
impossible to fully recover the exact original, allowing greater size reduction (for
example, JPEG). [True/False]
A) True
B) False
Answer: True
Explanation: Lossy compression deliberately discards some information to reduce size; because
that information is removed, the original cannot be exactly reconstructed. Lossy methods
generally achieve higher compression ratios and are used when perfect fidelity is not required
(e.g., JPEG for photos).
Q5. Lossless compression preserves all original data and allows full recovery of
the original, though it usually achieves less compression than lossy methods (for
example, PNG). [True/False]
A) True
, B) False
Answer: True
Explanation: Lossless compression reduces data size while preserving all original information so
the exact original can be reconstructed. Because no data is thrown away, lossless methods
usually compress less than lossy ones (PNG is a common lossless image format).
Q6. Explain what lossy compression is and why it can produce higher
compression ratios; refer to the example in the text. [Short Answer]
Answer: Lossy compression intentionally discards some original data to achieve much
smaller file sizes, which prevents perfect recovery of the original—JPEG images are a
common example where detail is thrown away for greater compression.
Explanation: Lossy methods trade fidelity for size by removing information deemed less
important, so they compress more effectively than lossless approaches. A complete answer states
that data is thrown away, notes the irreversible nature of the process, and cites JPEG as the
illustrative example provided.
Q7. Explain what round-off error is and how limited bit precision leads to it,
using the π example from the text. [Short Answer]
Answer: Round-off error occurs when there aren't enough bits to represent a number
exactly, so the value is approximated (for example, storing π with three digits as 3.14),
producing small differences from the true value.
Explanation: Limited precision means some real numbers cannot be stored exactly; rounding or
truncation produces a nearby representable value. A complete answer names limited bit
precision as the cause, describes approximation (rounding), and uses the π example to show how
digits are cut off.
Q8. Which scenario best exemplifies an overflow error in a digital system?
[Multiple Choice]
A) A car odometer rolls from 99999 to 00000 because the bits available can't represent
the larger value
B) A program records π as 3.14 because only a few digits are stored
C) An image saved as JPEG looks slightly degraded after compression
D) A photo file lists aperture, GPS coordinates, and timestamp
Answer: A car odometer rolls from 99999 to 00000 because the bits available can't
represent the larger value
