Edexcel GCSE Computer Science (1CP2) Exam Questions

• A 32 (1)
• The only correct answer is A. The correct answer is 32.
• B is not correct because 33 is the ASCII code for the exclamation mark (!)
• C is not correct because 48 is the ASCII code for the character 0
• D is not correct because 65 is the ASCII code for the uppercase letter A

• A Colour depth (1)
• The only correct answer is A. The correct answer is colour depth.
• B is not correct because image size is the width and height of the image in pixels
• C is not correct because resolution is the number of pixels per unit length, such as pixels per inch
• D is not correct because storage size is the amount of storage the image file uses

• A Amplitude (1)
• The only correct answer is A. The correct answer is amplitude (the height of the sound wave).
• B is not correct because bit depth is the number of bits used to store each sample
• C is not correct because sample interval is the time between samples
• D is not correct because sample rate is the number of samples taken each second

Award one mark for any of the following:

• The number of bits per pixel (1)
• The number of bits used to represent/store the colour of each pixel (1)

Allow bit depth

Do not accept the number of colours a pixel can have on its own

Do not accept the number of pixels in the image (this is the resolution/image size)

Award one mark for:

• The number of bits used per sample (1)

Allow bits per sample

Allow the number of bits used to record/store each sample

Do not accept the number of samples taken per second (sample rate)

Do not accept the number of bits used to store the whole sound file

Do not accept the number of levels/amplitude values a sample can take

Award one mark for any of the following up to a maximum of two marks:

• A set/collection of characters (1)
• (Characters such as) letters, digits and symbols/punctuation (1)
• Each character is represented by a unique code/binary value (1)
• A standard set of characters so that text can be exchanged between computer systems (1)

Allow 'a list of characters that a computer can represent' for the first mark.

Do not accept a program/software that converts text into binary.

Do not accept 'a set of binary codes' on its own.

Award up to two marks for a linked description such as:

• The height of the wave is measured at each sample (1) and stored as a binary value (1)
• The amplitude at a sample point is converted into a binary number using the bit depth (1) so each sample stores the height of the wave (1)
• A larger amplitude is stored as a larger binary value (1) so louder parts of the sound are represented by higher values (1)

Do not accept answers that only define amplitude as the height/loudness of the wave.

Do not accept answers about the number of samples taken each second (sample rate).

Award up to two marks for a linked description such as:

• A higher sample rate means more samples are taken each second (1) so more binary values are stored to represent the sound (1)
• A higher sample rate records the wave more frequently (1) so the binary representation follows the shape of the analogue wave more closely/is more accurate (1)
• A lower sample rate records fewer samples (1) so the binary representation is less detailed/less accurate (1)

A statement about the effect of sample rate on sampling (e.g. more/fewer samples) without a link to the binary representation scores a maximum of one mark.

A definition of sample rate on its own, with no effect on sampling, scores no marks.

Accept 'more accurate' for the second mark only when linked to more samples or binary values being stored, for example by 'so', 'which means' or 'because'.

Do not accept responses that describe sample interval or bit depth instead of sample rate.

Do not accept 'a higher sample rate means more bits per sample' or 'higher resolution', as these describe bit depth.

Do not accept a larger file size unless it is linked to more samples/binary values being stored.

For both marks, the expansion must follow/associate with the statement.

Award up to two marks for a linked explanation such as:

• More binary data is stored for each pixel (1) because a higher colour depth uses more bits per pixel (1)
• Each pixel has a longer binary code (1) so more storage is needed to hold the image (1)
• More colours can be represented (1) so more bits are needed for each pixel (1)
• The file contains more bits in total (1) because colour depth is the number of bits per pixel (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'more bits per pixel' for one mark.

Do not accept 'more pixels' or 'higher resolution' as the reason, because changing colour depth does not change the number of pixels.

Award up to two marks for a linked explanation such as:

• Fewer samples are taken every second (1) so less detail of the sound wave is captured (1)
• Fewer samples are taken every second (1) so the file is smaller/uses less storage space (1)
• The wave is measured less often (1) so parts/changes in the wave between samples are missed (1)

For both marks, the expansion must follow/associate with the statement.

The 'fewer samples are taken/measured less often' point can only be credited once; the second mark is for a valid expansion linked to it.

Do not accept restating the question, e.g. 'the time between measurements is longer' or 'the sample interval is longer', as either the point or the expansion.

Do not accept 'the sample rate is lower' as the expansion, as this says the same thing as a longer sample interval.

Do not accept 'the sound is lower quality/less accurate' on its own without saying what is lost, e.g. less detail of the wave captured/parts of the wave missed.

Do not accept answers about using fewer bits per sample or about compression, as these do not follow from the sample interval.