## AP CSP Exam Preparation

In this series of articles we will explain some of the sample questions that are provided to help AP CSP students help with exam preparation.

## Computing

This article focuses on the AP CSP exam questions related to computing. This includes the initial areas of how the computer uses binary such as in bits and bits, precision, and in digital media.

## Sample Exam Questions

We have taken examples from the sample questions from the two practice question sets from 2021 and from previous practice exercises provided by the college board.

Although it does not mean these are going to be in the exam, it is assumed that the primary areas of computing, programming, networks, data and algorithms will form most of the CSP exam.

These articles will present and explain questions and answers in these areas.

## What type of computing questions will be in the CSP exam?

We don’t know. But we do know that during the AP CSP course we have learn about bits, bytes, binary, errors, encoding and compression.

In other areas of computing we have seen simulations and innovations, whilst other details concerning copyright and interfaces are also included in the practice tests.

## Practice Exam questions

Read the questions and check your answer with the explanation below. We want to help everybody so if you think the question is easy then move on to the next question without reading the solution if you wish.

Some questions have more than one answer – these multiple answer questions are also in the AP CSP exam.

## Bit

Which of the following can be stored in a bit?

**A**. The results of a number MOD 2**B**. A Boolean variable**C**. A variable that could hold a range of positive values**D**. A computer that can be on, off, or in “sleep” mode

**This question has two answers.**

A bit can store two options so mod 2 gives 0 or 1, so A is an answer, a boolean is true or false, so B is also a correct answer.

Holding a range of values is more than two so C is incorrect, as is D as it has three options.

**Answer: A and B**

## Binary

Convert the binary number 10011011 to decimal?

**A**. 154**B**. 155**C**. 157**D**. 9F

The binary number represents 1 then 2 then 4 then 8 etc. s we can count the 1’s as follows: 128,0,0,16,8,0,2,1.

The total is 128+27=155

**Answer: B**

## Errors

The largest number a bank’s computer can store 2

^{31}– 1 or 2,147,483,647. After you deposit the amount of $2.,500,000,000.00, what will the result be?

**A**. Your winnings were more than the largest number the bank’s computer could hold, so an overflow error will occur.**B**. Since decimal numbers are stored imprecisely in computers, a rounding error occurred.**C**. The amount will be represented in machine code format, so converting it to decimal will show the balance in a more readable format.**D**. The amount will be represented in hexadecimal, so converting it to decimal will make the balance more readable.

If you had the binary number 1111 then this has the decimal value of 15, so if you tried to represent 16 then this would not be possible and the computer would give an error.

This type of error is called an integer overflow error as it can’t represent the integer and it overflows to another area. So A is the answer.

**Answer: A**

A cash register shows your change as $0.0499999 rather than $0.05. How is this possible?

**A**. The cash register DISPLAY procedure has an error**B**. Since decimal numbers are stored imprecisely in computers, a rounding error occurred**C**. It’s displaying the change owed in a different currency**D**. The amount is represented in hexadecimal rather than decimal.

Imagine if you divided 10 by 3, this would give 3.333… so the computer would have to stop at sometime and round the number down or up. Then multiply 3.33 by 3 and it gives 9.99 not 10.

This type of error is called a rounding error or even a floating point rounding error. Therefore the answer is B.

**Answer: B**

## Encoding

If a program is expecting a data field to contain a string, using a section of the ASCII table below, how will the code interpret the binary number 01101010 for that data field ?

**A**. 106**B**. 6A**C**. 152**D**. j

In the table we have the binary in decimal (106), hex number (6A), in binary, octal, and in the data it represents which is the character ‘j’. So the answer is D. J.

**Answer: D**

## Compression

A video is too large to send. How can the video be compressed to get it sent in full resolution?

**A**. Lossless compression will allow it to be sent in full resolution**B**. Lossy compression will make the file small enough to send**C**. They should be combined for the best compression**D**. Any compression technique will be sufficient

The key to this question is the need for full resolution which means no loss during compression i.e. lossless. So lossy losses information so that rules out B and C, whilst D is not true.

The answer is option A is correct.

**Answer: A**

## Hex numbers

You receive an error message in hexadecimal format of F1. Convert F1 from hexadecimal to decimal to get the correct error message?

**A**. 239 – Invalid operation**B**. 240 – rounding error**C**. 241 – overflow error**D**. 404 – error message not found

When we see a binary number like 1011 then we know the 1 or 0 represents 8,4,2,and 1, this is base 2. Hex numbers are base 16 like 256,16,1.

So hexadecimal format means 0-9 like normal and A-F represents 10 to 15.

So F1 will be F, which is 15, multiplied by 16, which equals 240, plus 1*1, so 241.

The answer is just 241, the rest is not important.

**Answer: C**

You want to match the color for your favorite college team listed in decimal as (75, 156, 211). Which of the following hexadecimal options is this color (Red, Green, Blue)?

**A**. #B49C133**B**. #411C9134**C**. #4B9CD3**D**. #B4C93D

We now know hex numbers are base 16 like 256,16,1.

So we can look at each pair of digits that represent a color. B4 starts two answers so we can check to see if this equals 75 first.

B represents 11, multiplied by 16 is 176, plus 4 equals 200. So not A or D.

41 would be 4*16 which equals 64, plus 1 equals 65, so not B.

If we change the second digit to B, that is 11, then 4B would be 64+11, which would be correct, 75.

You can check the rest, perhaps in the exam you would answer C and go back to check the rest when you have finished and checking your answers again.

**Answer: C**

## AP CSP exam practice questions: general computing

So far we have covered the digital computing questions. There are other general computing questions such as innovation and simulations. Here are some examples.

## User Interfaces

You are designing a UI (user interface) for use by multiple international travelers. How can you best communicate the options and features of the software program so most people can understand them?

**A**. Write the UI in Spanish and Chinese, two of the most common languages spoken worldwide**B**. Use an API to interface with a translation website for those who need it**C**. Provide a link to an online dictionary so words users do not know can be quickly looked up**D**. Use images to represent features of the program

Designing so most people can understand means keeping it simple like images.

Writing in two languages doesn’t help other travelers, translation website might help but they are not great, link to a dictionary worse than the translation.

So this question would require the best answer rather than the only correct one, so we would go for D.

**Answer: D**

## Copyright

What is the purpose of the DMCA?

**A**. To provide protection for intellectual property in digital format that has copyright status**B**. To enable music and movie downloads and streaming for wider sharing of people’s creative works**C**. To give acknowledgement to the creator of a digital work when it is used by others**D**. To provide the software to share digital files legally

DMCA is the software that stops people trying to copy CDs and digital music.

So A seems correct, B and D are the opposite of this restriction, and C is incorrect.

**Answer: A**

## Simulation

Which of the following statements describe a limitation of using a computer simulation to model a real-world object or system?

**A**. Computer simulations can only be built after the real-world object or system has been created**B**. Computer simulations only run on very powerful computers that are not available to the general public**C**. Computer simulations usually make some simplifying assumptions about the real-world object or system being modeled**D**. It is difficult to change input parameters or conditions when using computer simulations

Limitations of simulations. Option A is not true as the whole point of models is often to test before the real thing is built, and also D is false as testing parameters is also an important aspect of simulations.

Simulations are often built on expensive, powerful computers, but they can run on the internet for example.

Whilst simulations do have to make assumptions and can’t simulate everything otherwise they would be too complicated. So C would seem reasonable.

**Answer: C**

A simulation for a new app to allow students to place a lunch order by 11:00 a.m. to speed up the lunch line is being tested. what information will the simulation provide? Select two answers.

**A**. If a new line at the pick-up station will cause a slowdown**B**. If students will use the app often enough to make it worth the cost of developing**C**. If the app will decrease the cost of wasted food**D**. If the app can speed up the lunch line

**This question has two answers.**

The simulation is about the line and speed of the line. So A and D are about the speed of the line.

It can’t say if users will use an app, or the consumption of food.

**Answer: A and D**

## Citizen Scientists

Why are “citizen scientists” being used on projects? Select two answers.

**A**. They can record local data to be included in global databases**B**. They are paid minimum wage**C**. They can record data over a longer period of time**D**. To keep retired scientists involved in their area of expertise

**This question has two answers.**

Again we have a question with multiple answers. So lets look at which solutions are possible options.

They can record local data and that makes sense as a scientist can’t go everywhere so using local help would be sensible.

They are normally volunteers so B is wrong.

They record data over a longer period of time could be true. On a project that requires large quantities of data, having many people record small things but over time , does build up to valuable data.

Keeping retired scientists is not correct, so both A and C appear to me the correct answers.

**Answer: A and C**

## Computing Innovations

Which of the following are benefits resulting from technological innovations in education? Select two answers.

**A**. Online courses are available if a school cannot teach a specific course**B**. Online textbooks are available during the school day**C**. Classes can participate in virtual field trips**D**. The digital divide is minimizing the gap of educational opportunities available to all

**This question has two answers.**

Technological innovations would include online courses if not available, but not textbooks online.

Virtual field trips would be advantageous as we can’t always visit places, whilst the digital divide is not minimizing any gap it is describing the gap.

So A and C are the stand out options.

**Answer: A and C**

## More AP CSP exam practice questions

This is the first of a series of articles that take questions from the sample practice exams. The next article is about network questions. Click on the following link to see this article: Network Questions in the Computer Science Principles AP CSP Exam

The third article is now also available with programming questions. Here is the link: Programming Questions in the Computer Science Principles AP CSP Exam

If you wish to see an overview of the sample questions related to the AP CSP exam, please visit the following article:

Ultimate Guide to AP Computer Science Principles Exam Questions

## AP CSP exam webpage

For all courses, articles and information relating to the AP Computer Science Principles Exam, see our dedicated web page. Click the following link to visit this webpage: AP CSP Exam webpage

## Big Ideas exam practice questions

There are also practice questions grouped by the ‘big ideas’ that are here in pdf format.

So, if you want free download AP CSP questions and answers, then click on the big idea: