# Computing: Representing Data

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What number system do modern computers work in?
Binary
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What is binary?
A number system with just two symbols: 0 and 1
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What is binary made up of?
Data and instructions
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What is each digit in binary called?
A bit Binary digIT
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What is a kilobyte?
1024 bytes
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What is a terabyte?
1024 gigabytes
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What is a byte?
8 bits
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What is a gigabyte?
1024 megabytes
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What is a nibble?
4 bits
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What is a megabyte?
1024 kilobytes
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If you were adding a binary number and a column had 1 and 1, what would be the answer?
Write 0 and carry 1
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If you were adding a binary number and a column had 1 and 0, what would be the answer?
Write 1 and carry 0
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If you were adding a binary number and a column had 0 and 0, what would be the answer?
Write 0 and carry 0
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All the symbols displayed by a computer are represented by a code. What does a computer do when it wants a symbol to be displayed?
The computer looks up the symbol matching the code from a list of codes and their associated characters. The list of codes and matching characters is the character set for the computer.
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What are the codes used stored in?
Binary
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What determines how many characters or symbols can be used?
The number of bits used to store the code
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What does ASCII use?
7 bits, 127 characters or symbols plus the null character (128 in total)
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What does Extended ASCII use?
8 bits, 256 characters or symbols
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What is Unicode?
Can provide a character set for a computer that includes a wide range of specialist symbols. ASCII could be considered a subset of Unicode as Unicode keeps the original 127 ASCII codes.
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What does UNICODE use?
16 bits, 65,000 possibilities or 32 bits providing over 4 billion possibilities
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When we sort words in ASCII, what word would come first: 'zebra' or 'apple'?
Zebra
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On a computer, images are stored as what?
Many binary values
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How is the computer able to work out how to turn these binary values into the image?
The file with the binary data contains metadata (data about the data).
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What is a pixel?
One tiny square of the image.
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What does the number of bits we use for a pixel determine?
How many colours each pixel can represent. 1 bit can represent just two colours, 2 bits can represent 4 colours, 8 bits can represent 256 colours, 16 bits can represent 65,536 colours
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The more bits per pixel (bpp), the...
...greater the colour depth and the more bits we need to store the data.
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What is 16 bpp called?
High colour
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What is 24 bpp called?
True colour
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What does resolution mean?
The number of pixels per unit.
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The more pixels per inch, the...
...more data to be stored and the large file needed to store the image.
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What happens if a bitmapped image is enlarged on the screen?
The image size does not change. The pixels become bigger and the image becomes pixelated or 'blocky'.
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How many colours can be represented using a 4-bit colour depth?
16
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What are the main factors effecting the size of the file needed to store an image?
The resolution, the size and the colour depth.
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What are sound files described by?
Metadata to make sure the computer can interpret the data accurately
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What does the data stored include?
Audio codec, sample rate.
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What needs to be done to sound to get it transferred to a computer?
Needs to be converted from analogue to digital
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What is a sample interval?
Describes the sample rate, the time between samples being taken. The higher the sample interval the lower the sample rate.
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When sound is sampled at a low rate it...
Very few samples are taken. There is a poor match between the original sound and the sampled sound, a small file size is required.
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When sound is sampled at a high rate it...
Many more samples are taken, there is a good match between the original sound and the sampled sound, a large file size is required.
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What is the bit rate?
The amount of space used for each sample.
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What does a higher bit rate mean?
More accurate sampling at each point which gives better quality, more data needs to be stored which needs a larger file size
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What happens when a computer is instructed to run a program?
The computer is directed to a specific location in memory that contains the first instruction in the program.
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The CPU fetches the instruction and decodes it in order to find out what to do next. What is the instruction made up of?
The operator: instruction part, and the operand: data part.
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What is the accumulator?
A special register in the CPU used to store the results of any calculation.
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What can the CPU not tell the difference between?
Data and instructions which simple deals with what it finds according to what it expects to find.
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## Other cards in this set

### Card 2

What is binary?

#### Back

A number system with just two symbols: 0 and 1

### Card 3

#### Front

What is binary made up of?

### Card 4

#### Front

What is each digit in binary called?

### Card 5

#### Front

What is a kilobyte?