Data Storage & Compression (OCR GCSE Computer Science)

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.

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.