Data Storage & Compression (OCR GCSE Computer Science): Exam Questions

A student compresses all their documents before emailing them to their teacher

Give two benefits of compressing the data before it is emailed.

Explain why lossy compression may not be appropriate to compress all of the student’s files.

The sample rate is increased on a computer when recording music from a guitar.

Give two effects this will have on the recording.

Complete a 2-place shift to the right on the binary number 11001011.

Explain the effect of performing a 2-place shift to the right on the binary number 11001011.

The table gives the ASCII code for the characters.

Explain how the word MOP will be represented in ASCII.

Computers make use of electronic switches called transistors.

Describe how transistors can be used to store a value in binary.

Azmi says, “hexadecimal is used because it takes up less storage space in the computer’s memory than binary.”

Tick one box to identify whether Azmi is correct.

Justify your answer.

Binary shifts can be used for multiplication and division.

Draw one line from each shift on the left to its correct outcome on the right.

Add the following 8 bit binary integers, giving your answer in binary.

Ali’s tablet computer has 100GB of secondary storage. There is currently 80GB available.

Ali wants to transfer a series of video clips onto his tablet. Each video is, on average, 200000 kilobytes.

Calculate an estimate of the number of video clips Ali can fit onto his tablet.

Show your working.

Give two reasons why computer scientists use hexadecimal to represent numbers instead of binary.

Show the outcome of a right shift of three places on the binary value 0111 1000.

The following logo is stored as a bitmap image.

Each box represents one pixel, with three different colours being used in the image.

Calculate the fewest number of bits that could be used to store the logo as a bitmap image.

You must show your working.

A radio station uses a digital camera to take a photograph of a computer scientist for their website. The photograph is stored as a bitmap image.

Describe how bitmap images are represented in binary.

Explain why computers represent data in binary form.

An image is compressed using lossy compression before being uploaded to a radio station’s web server.

The image will be used on the radio station’s website.

Describe one advantage and one disadvantage of using lossy compression on the image that will be used on the website.

Convert the hexadecimal number A3 to denary.

Show your working.

Add the following binary numbers.

William transfers videos to a computer for editing.

The computer has 1GB of storage free.

Calculate the number of videos that could be stored on the computer if each video was 100MB in size.

Show your working.

Show the effect of a binary shift right of two places on the binary number 00110100.

Describe a shift that can be used to double the value of the binary number 00100100.

The table below (Fig. 3) shows the ASCII codes for a number of characters.

The lower case ASCII code for a character can be found by adding 00100000 to the upper case version.

Fig. 3

Complete the table above by filling in the missing ASCII codes.

The following table has either the binary or denary value of 3 numbers.

Complete the table by converting the 8-bit binary number into denary and the denary number into 8-bit binary.

Complete the table by writing the answer to each statement

Add these two 8-bit binary numbers using binary addition.

Show your working out.

Explain how changing the bit depth will affect a sound file.

The musician’s recordings have an average (mean) file size of 3 MB. The musician has 1000 recordings.

Calculate an estimate of the storage space in GB that the 1000 files will require, assuming they are each 3 MB in size.

Show your working out.

A software developer is creating a mobile application. Each image file used in the application has an average (mean) file size of 2 MB. The application contains 500 image files.

Calculate an estimate of the storage space in GB that the 500 files will require, assuming they are each 2 MB in size.

Show your working out.

Add the following binary numbers.

Add the following binary numbers.

A student is creating a range of documents for a school project.

The student records a podcast about computer science.

Describe how an analogue sound wave is converted into digital form.

Tick (✓) one or more boxes on each row to identify the effect(s) that each change will have on the sound file.

A computer records an audio file of someone playing a guitar.

Describe what happens when the computer converts the music into a file.

Sound data is sampled and stored in binary.

A 30-second section of sound data is sampled at a rate of 48KHz using 24 bits per sample.

Describe the data that is recorded when sound is sampled.

Explain what is meant by a sample rate of 48KHz.

Describe how the file size of the sound recording could be reduced.

Describe how to convert a 2-digit hexadecimal number into denary.

Use an example in your answer.

Calculate the 8-bit binary representation for the denary number 253

Calculate the 8-bit binary representation for the denary number 189.

A network packet contains the 8-bit binary value 11010111.

Calculate the denary equivalent and state whether the result is odd or even.

A sensor reading is stored as the 8-bit binary value 10110101.

Calculate the denary equivalent and state whether the result is odd or even.

Convert the denary number 189 into a 2-digit hexadecimal value.

Show your working.

Convert the denary number 227 into a 2-digit hexadecimal value.

Show your working.

A colour code is stored as the hexadecimal value E7.

Calculate the denary value of this colour code.

Show your working.

A memory address is stored as the hexadecimal value B4.

Calculate the denary value of this memory address.

Show your working.

A MAC address segment is represented by the binary string 11101101.

Convert this value into a 2-digit hexadecimal number.

Show your working.

A network interface card uses the binary value 10110011 as part of its unique identifier.

Convert this binary value into a 2-digit hexadecimal number.

Show your working.

Convert the hexadecimal value A9 into an 8-bit binary number.

Show your working.

Convert the hexadecimal value F3 into an 8-bit binary number.

Show your working.

Perform a 3-place left shift on the binary number 00010100.

Evaluate the effect this has on the original denary value.

Perform a 4-place right shift on the binary number 11010000.

Evaluate the effect this has on the original denary value.

A developer is creating a custom character set to represent 500 unique symbols.

Explain the minimum number of bits required to store each character and evaluate the impact this would have on file size compared to using 7-bit ASCII.

In an 8-bit Extended ASCII system, the character A has the denary value 65.

Calculate the binary representation of the character J and explain why an 8-bit system is needed for modern symbols such as the copyright sign (©).

A global social media platform moves from 8-bit Extended ASCII to 16-bit Unicode.

Analyse the benefit of this change for international communication and evaluate the impact on secondary storage.

An image’s colour depth increases from 8 bits to 24 bits, and its resolution doubles in both height and width.

Calculate the factor by which the file size increases and analyse the effect on image quality.

Identify which items of metadata are required to correctly display a bitmap image and explain how metadata helps manage large photo libraries.

A video-on-demand service streams 4K video to mobile users.

Evaluate the need for compression in this scenario.

A musician emails a high-quality audio recording to a producer for a quick review.

Justify the use of lossy compression for this task.

A business archives its legal financial contracts digitally.

Analyse why lossless compression is the only suitable option.