Computer Science A-Level 2015 May -
June 9608/11
1. i) Convert the following binary number into hexadecimal:
1 0 1 1 1 0 0 0 - correct answer-B 8
1. ii) Convert the following denary number to BCD format:
97 - correct answer-1 0 0 1 0 1 1 1
1. iii) Using two's complement, show how the following denary number could be stored in an
8 - bit register:
114
-93 - correct answer-114 - 0 1 1 1 0 0 1 0
-93 - 1 0 1 0 0 0 1 1
2. a) Sound can be represented in a computer in a digital format
i) Give the definition of the term sampling - correct answer-Any *one* from:
- Amplitude of sound wave taken at different points in time
- Measurement of value of analogue signal at regular time intervals/a point in time.
2. a) ii) Give *one* reason why 16-bit sampling is used in an audio compact disk (CD). -
correct answer-Any *one* from:
- Bit depth/sampling resolution sufficient for good quality sound
- Higher bit depth/sampling resolution would mean bigger files
- ...hence less (music) content on each CD
- Can represent dynamic range of about 90 dB
- 90 dB is basically the maximum dynamic range of human hearing
- Compromise between quality and reasonable file size
2. a) iii) Explain what is meant by the term sampling resolution. - correct answer-Any *two*
from:
- Resolution is the number of distinct values available to encode/represent each sample
- Specified by the number of bits used to store/record each sample
- Sometimes referred to as bit depth
- The higher the sampling resolution, the smaller the quantization error
- A higher sampling resolution results in less distortion of the sound
- Usually 8 bit, 16 bit, 24 bit or 32 bit
2. a) iv) Give *one benefit* and *one drawback* of using higher sampling resolution. - correct
answer-Benefit:
- Allows for larger dynamic ranges
- ...as dynamic range is approximately six times the bit depth
- More accurate representation/crisper sound quality
Drawback:
, - Bigger files/occupies more memory/storage
- Longer to transmit data/download music
- Greater processing power needed
2. b) Describe *two* typical features found in software used for editing sound files. - correct
answer-Any *two* from:
- Edit start time, stop time and duration of any sound/timeline
- Extract/Delete/Save part of a clip
- Frequency, amplitude, pitch alteration
- Fade in/out of a clip
- Mix/Merge multiple sound sources/tracks
- Combine different sources at various volume levels
- Pan between tracks/channels- Use of filters
- Playback to speakers, processors or recording medium
- Conversion between different audio file formats
2. c) Explain the difference between lossless and lossy data compression techniques. -
correct answer-Any *three* from:
- Lossless designed to lose none of the original detail/lossless allows original file to be
recreated exactly
- Lossless technique based on some form of replacement
- Mention of type of replacement, for example RLE, FLAC etc.
- By example: e.g. 000-1111-222222-333 = 3-0, 4-1, 6-2, 3-3 etc.
- Maximum compression about 50%
- Lossy may result in loss of detail compared to original file/lossy does not allow original file
to be re-created exactly
- Lossy techniques make decision about what parts of sound/sound file are important and
discards other information
- Only keeps sounds human ear can process/discards sounds most people cannot hear
- ... then applies lossless technique, for further reduction
- Lossy compression can reduce to about 10%
- An example of jpeg, mp3 or other correct examples of compressed formats.
3. Five modes of addressing and five descriptions are shown below. Draw a line to connect
each mode of addressing to its correct description. - correct answer-Direct --> the operand is
the address of the value to be used
Immediate --> the operand is the value to be used
Indexed --> the operand plus contents of index register is the address of the value to be
used
Indirect --> the operand is the address of the address of the value to be used
Relative --> the operand is the offset from the current address where the value to beused is
stored
4. a) Sensors are one type of input device. For each of the following situations, name a
different sensor that could be used.
i) air conditioning in an office building - correct answer-temperature/thermistor
June 9608/11
1. i) Convert the following binary number into hexadecimal:
1 0 1 1 1 0 0 0 - correct answer-B 8
1. ii) Convert the following denary number to BCD format:
97 - correct answer-1 0 0 1 0 1 1 1
1. iii) Using two's complement, show how the following denary number could be stored in an
8 - bit register:
114
-93 - correct answer-114 - 0 1 1 1 0 0 1 0
-93 - 1 0 1 0 0 0 1 1
2. a) Sound can be represented in a computer in a digital format
i) Give the definition of the term sampling - correct answer-Any *one* from:
- Amplitude of sound wave taken at different points in time
- Measurement of value of analogue signal at regular time intervals/a point in time.
2. a) ii) Give *one* reason why 16-bit sampling is used in an audio compact disk (CD). -
correct answer-Any *one* from:
- Bit depth/sampling resolution sufficient for good quality sound
- Higher bit depth/sampling resolution would mean bigger files
- ...hence less (music) content on each CD
- Can represent dynamic range of about 90 dB
- 90 dB is basically the maximum dynamic range of human hearing
- Compromise between quality and reasonable file size
2. a) iii) Explain what is meant by the term sampling resolution. - correct answer-Any *two*
from:
- Resolution is the number of distinct values available to encode/represent each sample
- Specified by the number of bits used to store/record each sample
- Sometimes referred to as bit depth
- The higher the sampling resolution, the smaller the quantization error
- A higher sampling resolution results in less distortion of the sound
- Usually 8 bit, 16 bit, 24 bit or 32 bit
2. a) iv) Give *one benefit* and *one drawback* of using higher sampling resolution. - correct
answer-Benefit:
- Allows for larger dynamic ranges
- ...as dynamic range is approximately six times the bit depth
- More accurate representation/crisper sound quality
Drawback:
, - Bigger files/occupies more memory/storage
- Longer to transmit data/download music
- Greater processing power needed
2. b) Describe *two* typical features found in software used for editing sound files. - correct
answer-Any *two* from:
- Edit start time, stop time and duration of any sound/timeline
- Extract/Delete/Save part of a clip
- Frequency, amplitude, pitch alteration
- Fade in/out of a clip
- Mix/Merge multiple sound sources/tracks
- Combine different sources at various volume levels
- Pan between tracks/channels- Use of filters
- Playback to speakers, processors or recording medium
- Conversion between different audio file formats
2. c) Explain the difference between lossless and lossy data compression techniques. -
correct answer-Any *three* from:
- Lossless designed to lose none of the original detail/lossless allows original file to be
recreated exactly
- Lossless technique based on some form of replacement
- Mention of type of replacement, for example RLE, FLAC etc.
- By example: e.g. 000-1111-222222-333 = 3-0, 4-1, 6-2, 3-3 etc.
- Maximum compression about 50%
- Lossy may result in loss of detail compared to original file/lossy does not allow original file
to be re-created exactly
- Lossy techniques make decision about what parts of sound/sound file are important and
discards other information
- Only keeps sounds human ear can process/discards sounds most people cannot hear
- ... then applies lossless technique, for further reduction
- Lossy compression can reduce to about 10%
- An example of jpeg, mp3 or other correct examples of compressed formats.
3. Five modes of addressing and five descriptions are shown below. Draw a line to connect
each mode of addressing to its correct description. - correct answer-Direct --> the operand is
the address of the value to be used
Immediate --> the operand is the value to be used
Indexed --> the operand plus contents of index register is the address of the value to be
used
Indirect --> the operand is the address of the address of the value to be used
Relative --> the operand is the offset from the current address where the value to beused is
stored
4. a) Sensors are one type of input device. For each of the following situations, name a
different sensor that could be used.
i) air conditioning in an office building - correct answer-temperature/thermistor
