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Edexcel GCSE Computer Science > Topic 3 - Data > Flashcards

Topic 3 - Data Flashcards

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1
Q

What is Binary?

A

A Base-2 numbering system. (only has 2 digits - 0 and 1)

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2
Q

What is Denary?

A

A Base-10 numbering system (from 0 - 9)

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3
Q

What is a nibble (in bits)?

A

4 bits.

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4
Q

When there is an extra digit in a binary calculation, what is this called?

A

Overflow.

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5
Q

What does ‘1’ represent in Sign and Magnitude?

A

Negative

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6
Q

What does ‘0’ represent in Sign and Magnitude?

A

Positive

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7
Q

What is a Hexadecimal?

A

A Base-16 numbering system (16 digits. It shares 0-9 with denary then uses letters A-F)

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8
Q

Why are Hexadecimals used?

A

They simplify long streams of bits

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9
Q

What are Real Numbers?

A

Numbers with an integer part and a fractional part.

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10
Q

What is the scientific notation of representing floating point binary?

A

Mantissa x Base^Exponent

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11
Q

What is the name of the subset that ASCII is in?

A

Unicode

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12
Q

Why is Unicode better than ASCII?

A

It can represent a wider range of characters (e.g. from other languages such as: é)

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13
Q

What is a Bitmap?

A

An image stored as an array of individual pixels.

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14
Q

What is a Pixel?

A

An individual picture element.

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15
Q

What is Colour Depth?

A

The number of bits allocated to represent each colour

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16
Q

What is ‘Resolution’ of an image?

A

The detail it holds within an image.

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17
Q

How can ‘Resolution’ be displayed as?

A

width x height OR the number of ‘Pixels Per Inch (PPI) ‘

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18
Q

What are Analogue Signals?

A

They’re continuous, they don’t have defined ranges, and are represented often by waves.

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19
Q

What are Digital Signals?

A

They form discrete values (they fall within a defined range and can only take certain values).

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20
Q

What are three everyday examples of Analogue Signals?

A

Sound, temperature and light intesity

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21
Q

What is Sampling?

A

The process of recording an analogue signal at regular intervals.

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22
Q

What is ‘Sampling Frequency’ ?

A

The average number of samples obtained per second. Measured in Hertz (Hz)

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23
Q

What is Quantisation?

A

The process of approximating the analogue values to predetermined discrete levels.

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24
Q

What is a bit?

A

1 or 0

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25
Q

What is a byte?

A

8 bits / 2 nibbles

26
Q

What is a Kilobyte (in bytes) ?

A

1024 bytes (2^10 bytes)

27
Q

What is a Megabyte in KB?

A

1024 KB (2^20 bytes)

28
Q

What is a Gigabyte in MB?

A

1024 MB (2^30 bytes)

29
Q

What is a Terabyte in GB?

A

1024 GB (2^40 bytes)

30
Q

What is the formula of Transfer Rate?

A

Transfer rate = b/s

31
Q

What is data compression?

A

The reduction of file size whilst retaining the underlying information.

32
Q

What is Lossy Compression?

A

Some of the original data is lost

33
Q

What are two examples of lossy algorithms?

A

MP3 (audio) and JPEG (images)

34
Q

What is Lossless Compression?

A

Compresses the data without losing any data

35
Q

What is an example of Lossless Compression?

A

Run-length encoding (RLE)

36
Q

How does RLE work?

A

It collects all the like terms together (e.g. y y y = 3y)

37
Q

What is encryption?

A

The process of making data secret to that only authorized viewers can decrypt and read the data, and third parties cannot.

38
Q

What are the 5 steps of encryption?

A
  1. Message written in plaintext
  2. Message is encrypted into ciphertext
  3. Message is sent
  4. Message is received
  5. Message is decrypted back into plaintext
39
Q

Why is encryption used (2 reasons) ?

A
  1. To protect data

2. To verify the sender

40
Q

How does a Caesar Cipher algorithm work?

A

Letters in the alphabet are shifted depending on the shift key

41
Q

What are the two arrangements of data?

A

Structured and unstructured

42
Q

What are the differences between structured and unstructured data?

A

Structured - arranged in an organised and defined way.

Unstructured - cannot be easily mapped by a computer in predefined fields.

43
Q

What is a Database?

A

A collection of information that is organised so that it can be easily accessed, managed and updated.

44
Q

What is a Relational database?

A

Consists of tables linked together with each other by key fields.

45
Q

What is a table?

A

A two-dimensional representation of data that is stored in rows and columns.

46
Q

What is a Field?

A

Single piece of data about an entity

47
Q

What is a Record?

A

The group of fields about a specific entity (a row)

48
Q

What is a Report?

A

A presentation of data from the database

49
Q

What are Queries?

A

Requests of data stored in the database

50
Q

What is an Entity?

A

An object/person/thing about which data is stored.

51
Q

What is an Entity Relationship?

A

A model used to identify entities and how they relate when designing a database.

52
Q

What is a relationship?

A

Link between entities.

53
Q

What is a primary key?

A

A field that uniquely identifies a record.

54
Q

What is a Composite Key?

A

A combination of fields in a table used to uniquely identify a record.

55
Q

What is a Foreign Key?

A

A field in one table that is a primary key in another table.

56
Q

What is Structured Query Language (SQL) ?

A

A specialised programming language for creating database structures and managing data in them.

57
Q

What does INSERT do?

A

Enters a record into the table and stores the value in the specified column.

58
Q

How does INSERT work?

A

INSERT INTO TableName (Field1, Field2…)

VALUES (“abc123”, “abc123”)

59
Q

How do you create a table?

A

CREATE TABLE TableName

ColumnName datatype, …

60
Q

How do you UPDATE something?

A

UPDATE TableName
SET (ColumnName = Value, …)
WHERE ;

61
Q

How do you DELETE something?

A

DELETE * FROM TableName; (deletes everything)

DELETE FROM Student
WHERE Student

62
Q

How do you SELECT something?

A

SELECT (ColumnName)
FROM TableName
[WHERE ]
[ORDER BY (ColumnName,…)];

Edexcel GCSE Computer Science (6 decks)

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