1
Q
Analogue to Digital (A2D) Conversion
A
The process of converting analogue sound waves into a digital format by recording samples of the amplitude at points in time and storing them as binary.
2
Q
ADC Converter
A
Converts analogue data to digital data
3
Q
Analogue Data
A
Data values that are continuously changing.
4
Q
Describe how sound is represented in a computer.
A
- Samples of the original analogue sound wave’s amplitude is recorded a certain number of times per second
- Each sample is assigned a corresponding binary code
- The binary number of each amplitude sample is saved in sequence
5
Q
ASCII
A
A 7 bit character set providing 128 unique codes, primarily used to represent characters in the English language.
6
Q
What are the advantages of using ASCII over Unicode?
A
It takes a lot less storage space than Unicode.
7
Q
What are the disadvantages of using ASCII over Unicode?
A
- It can only represent 128 characters
- It cannot store special characters such as emojis
8
Q
What is extended ASCII?
A
- A character set that builds on normal ASCII as it uses an 8th bit, providing 256 unique codes
- It provides essential characters such as mathematical operators and more recent symbols
9
Q
What are the similarities between the ASCII and Unicode character sets?
A
- They both can use 8 bits
- They both each represent each character using a unique code
- ASCII is a subset of Unicode
10
Q
What are the differences between the ASCII and Unicode character sets?
A
- ASCII uses 7 or 8 bits to represent one character whilst Unicode can use up to 32
- ASCII only represents one language whereas Unicode can represent multiple
11
Q
How are words represented with ASCII?
A
Each character of the word has its own unique binary code. Each character in the word is replaced by its code; the codes are stored in order of the word.
12
Q
Band-Limiting Filter
A
Eliminates inaudible high frequency elements to avoid coding issues they may pose.
13
Q
Binary
A
A base 2 number system that uses only two digits, 0 and 1, fundamental to computer operations.
14
Q
BCD
A
Binary Coded Decimal - A number system that uses 4 bits to represent each denary digit from 0 to 9 individually, often used in systems requiring clear decimal display and precision.
15
Q
State some uses of BCD and why it is used for each point.
A
- electronic calculators: keeps numbers in decimal format for easier display and accuracy
- digital clocks and watches: since time is naturally decimal, BCD makes display logic simpler
- banking and financial systems: avoids rounding errors when doing decimal calculations, especially with money
- old digital systems/embedded systems: simpler to implement with hardware that displays digits individually
16
Q
State the benefits of using BCD to represent values.
A
- Avoids tiny rounding errors when converting fractional decimal numbers into binary
- Straightforward to convert to and from BCD and denary, making it less complex to encode and decode
17
Q
Binary Nibble
A
A group of 4 bits.
18
Q
Binary Prefix
A
A unit prefix used to indicate multiples of bytes in binary based on powers of 2.
19
Q
Bitmap Image
A
An image made up of a grid of pixels, where each pixel is stored as a unique binary code that represents its colour.
20
Q
Bit Depth/Colour Depth
A
- The number of bits stored per pixel, this determines the number of colours available.
- Higher colour depth = more colours available = more detail (higher quality)
21
Q
How does changing the colour depth of an image affect its file size?
A
Increasing the colour depth means more bits per pixel and thus more data stored, increasing the file size.
22
Q
Byte
A
A group of 8 bits.
23
Q
Character Set
A
- All the characters and symbols that can be represented by a computer system, with each character being assigned a unique binary code
- It provides a standard for computers to communicate and send/receive information
24
Q
Compression
A
The process of reducing the size of a file to take up less space on secondary storage and minimise transfer time.
25
What are the advantages of compressing images?
- Faster opening and transmission time
- Faster downloading time
- Uses less bandwidth
- Will take less space on secondary storage so that there is more space for other files
26
Denary
A base 10 number system that uses 10 digits from 0 to 9, also known as the decimal system.
27
Denary Prefix
A unit prefix used to indicate multiples of bytes in the denary system based on powers of 10.
28
Drawing List
Included in the file header of a vector graphic, contains:
- commands used to create each object in the image
- attributes that define the properties of each object
- relative position of each object
- stores the commands needed to draw each object for a vector graphic
29
Drawing Object
A component created using a formula.
30
Extended ASCII
An 8 bit character set that expands on standard ASCII, providing 256 unique codes to include non-English characters and more symbols.
31
File Header
Metadata stored at the beginning of a file, storing information such as:
- file type
- file size
- image resolution
- colour depth
- compression type
32
Hexadecimal
A base 16 number system that uses 16 digits from 0 to 9 and letters from A to F, often used in computing as a shorthand for binary.
33
What are the benefits of using hexadecimal over binary?
- It takes fewer digits to represent a given value in hexadecimal than in binary
- Easier for humans to read and spot mistakes
- Since numbers with more bits are more prone to errors when being copied, hexadecimal reduces this risk
34
Give some examples of where hexadecimal can be seen.
- MAC addresses
- IP addresses
- colour codes
- URLs
35
Image Resolution
- The total number of pixels that make up a bitmap image.
- In general, higher resolution = more detail (higher quality)
36
Describe the impact of increasing the image resolution on the quality of a bitmap graphic.
- More pixels can be stored
- The image will be sharper and less pixelated
37
Lossless Compression
A compression method where data is encoded to reduce file size, but no data is permanently lost, meaning the original file can be perfectly restored.
38
When is lossless compression suitable?
It is more suitable for data where a loss in quality is unacceptable, for example documents as it will cause the document to be corrupted.
39
Lossy Compression
A compression method where data is permanently lost during file size reduction, leading to a decrease in quality but greater compression. This change is irreversible.
40
When is lossy compression suitable?
For data where reducing quality is acceptable as it makes a small change, such as images, video, and sound.
41
Describe two methods for how lossy compression is used to compress images.
- Pixels with similar colours can be grouped together and assigned a singular colour code, reducing the amount of colours used in the image and the number of bits used to store each colour.
- The colour depth of the image can be reduced by changing each pixel code to an approximation stored with fewer bits.
42
Why should streaming a real-time video use lossy compression?
- Loss of quality will not be noticeable
- Needs to be viewed in real time so less bandwidth needed if file size smaller
- Smaller file sizes will reduce buffering so the video will play more smoothly
- Viewers may watch on different devices, so may not need high quality resolution
43
Why should streaming a real-time video use lossless compression?
- Original recording may not have been made in high resolution
- The reduction in file size is sufficient for the receiving device
- Could be streaming to high bandwidth devices
- Viewers do not want any loss of quality
44
MPEG-3 (MP3)
An audio compression format that uses lossy compression to significantly reduce the file size of music.
45
MPEG-4 (MP4)
A multimedia file format capable of storing audio, video, photos and animations, using compression to maintain high quality with small file sizes, often used for streaming.
46
Most Significant Bit (MSB)
The leftmost bit in a binary number, often used to indicate the sign of a number in signed representations like two's complement.
47
Number Base
The number of different digits or symbols a number system uses to represent values.
48
One's Complement
A method of representing both positive and negative binary numbers by inverting all the bits of a positive number to get its negative equivalent.
49
What are the disadvantages of one's complement?
It can have two representations for 0, positive and negative.
50
Overflow
An error that occurs when the result value of a binary arithmetic operation exceeds the set number of bits assigned.
51
Perceptual Music Shaping
A technique used in MP3 compression to remove sounds that humans generally don't notice, such as frequencies outside human hearing range or quieter sounds masked by louder ones.
52
Pixel
The smallest element of a bitmap image, stored as a unique binary code representing its colour.
53
Pixel Density
The number of pixels within a square inch of a display, indicating the sharpness of the image on a physical screen.
54
Property
Data about the shapes that defines one aspect of the appearance of the drawing object.
55
Run-Length Encoding (RLE)
A form of data compression that condenses repeating sequences of identical elements into a single value with a count, often used for images or text with repeating characters.
56
How would a text file be compressed?
- Through lossless compression, using the method run-length encoding
- Repeated sequences of characters are replaced by a single copy of the character with a count of how many times it was repeated.
57
Sampling Rate
The number of samples taken per unit time of an analogue sound wave, measured in Hertz (Hz). A higher sampling rate increases the quality of the digital sound wave.
58
Explain the effect of increasing the sampling rate on the accuracy of a sound recording.
- It improves the accuracy of the sound recording because the digital waveform more closely resembles the original analogue waveform
- Quantisation errors are reduced
- Increases amount of detail stored as the sound is recorded more often
59
Sampling Resolution
The number of bits used to represent each sound sample. A higher resolution allows for a wider range of amplitudes and thus better sound quality.
60
Explain the effect of increasing the sampling resolution on a sound file.
- More bits used to store each sound sample
- more amplitudes can be represented
- each amplitude in the digital recording is closer to the original
- quantisation errors reduced
- digital soundwave more accurate to the analogue one
61
Screen Resolution
the term for dots per inch when an image is displayed
62
Two's Complement
A method for representing both positive and negative binary numbers, where the leftmost bit is the MSB which indicates the sign of the denary value.
63
What are the advantages of using two's complement?
- It provides consistency as it eliminates the need for different rules for signed and unsigned numbers, allowing it to work for any combination of positive and negative values.
- It allows hardware simplicity as the same adder circuit can handle every binary arithmetic operation, and no special logic is needed to detect signs or subtract manually.
- As long as the result sum doesn't exceed the maximum value determined by the set number of assigned bits, any two positive numbers can be added without any issues.
64
Unicode
A universal character set that uses a minimum of 16 bits, providing a vast number of unique codes to represent characters from virtually all major languages and writing systems worldwide.
65
What are the advantages of using Unicode over ASCII?
- It can represent more characters than ASCII
- It can support all common characters around the world
- It can represent special characters such as emojis
66
What are the disadvantages of using Unicode over ASCII?
It takes a lot more storage space than ASCII.
67
Vector Graphic
An image created from mathematical equations and points, storing only the mathematical descriptions of shapes and lines.
68
What are vector graphics ideal for?
Situations where the same image will be scaled to be made bigger or smaller and a loss of quality is unacceptable.
69
What are the advantages of using vector graphics?
- It can be rescaled without a loss of quality as the mathematical equations that make up the graphic will be recalculated
- The file size of a vector graphic is generally smaller as it does not depend on image resolution as a bitmap image does
70
Describe the differences between a vector graphic and a bitmap image.
- Vector graphics are stored as mathematical equations and points whereas bitmap images are stored as a grid of pixels where each pixel is stored as a binary code representing its colour.
- Vector graphics don't reduce in quality when scaled as their mathematical equations can be recalculated whilst bitmap images will result in pixelation and lower quality.
71
Why are bitmap images usually compressed before being sent in an email?
- reduced bandwidth usage when transmitting the email
- reduced transmitting time
- reduced storage space in the email
- emails usually have a maximum size for attachment
CS a levels
flashcards
Decks in class (11)
# Cards
-
Chapter 1 - Information Representation71
-
Chapter 2 - Networks & The Internet146
-
Chapter 3 - Hardware55
-
Chapter 5 - System Software42
-
Chapter 4 - Processor Fundamentals56
-
Chapter 6 - Security, Privacy, and Integrity40
-
Chapter 12 - Software Development34
-
Chapter 7 - Ethics & Ownership33
-
Chapter 8 - Databases23
-
Chapter 10 - Data Types & Structures49
-
Chapter 9 - Algorithm Design & Problem Solving3
