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A level computer science > Exchanging data > Flashcards

Exchanging data Flashcards

1
Q

What are the characteristics of lossy compression?

A

Removes parts of the file.
For sound files removes the parts you cannot hear
Is permanent

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2
Q

What are the characteristic of lossless compression?

A

Finds patterns and other parts to note down
Is not permanent
Usually reduces it by less.

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3
Q

What is RLE (run length encoding)?

A

A type of lossless compression where patterns are found and made into one occurrence of the data followed by the number of times it occurs

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4
Q

What is dictionary encoding?

A

Another method of lossless compression, creates a dictionary of the words or numbers.

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5
Q

What is symmetric encryption?

A

Both the sender and receiver share the same private key. The private key is used to encode and decode

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6
Q

What is asymmetric encryption?

A

Two separate keys are used, one key is public and the other is private. The public is used to encrypt the private is used to decrypt.

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7
Q

What is hashing?

A

Hashing is when an input is turned into a fixed size value

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8
Q

What is a flat file database?

A

A database that consists of a single file

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9
Q

What is a primary key?

A

A primary key is a unique identifier for each record in a table.

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10
Q

What is the foreign key?

A

The foreign key is an attribute that links two tables together.

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11
Q

What is the secondary key?

A

A secondary key allows a database to be searched quickly.

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12
Q

What are the different relationships we can have between models?

A

One to one, one to many, many to many

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13
Q

What is normalisation?

A

The process of coming up with the best possible layout for a relational database.

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14
Q

What is first normal form?

A

There are no attributes that contain more than one value

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15
Q

What is second normal form?

A

A database doesn’t have any partial dependencies. This means that no attributes can depend on part of a composite key.

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16
Q

What is third normal form?

A

A database that contains no non key dependencies.

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17
Q

What is indexing?

A

Indexing is a method that is used to store the position of each record ordered by a certain attribute. This allows data to be looked up quickly.

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18
Q

What statements are necessary when creating a SQL statement?

A

SELECT, FROM, WHERE, ORDER BY

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19
Q

What does SELECT do in a SQL statement?

A

used to collect fields from a given table

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20
Q

What does FROM do in a SQL statement?

A

specifies which table the information will come from

21
Q

What does WHERE do in a SQL statement?

A

Can be used to specify even more for example a set of dates which you only want to see

22
Q

What does ORDER BY do in a SQL statement?

A

Specifies whether the data should be shown in ascending or descending order.

23
Q

How do you create a database in SQL?

A

CREATE TABLE Tablename
(
Attribute1 INTEGER NOT NULL, PRIMARY KEY,
Attribute2 VARCHAR(20) NOT NULL<
)
;

24
Q

How do you add columns in a table?

A

ALTER TABLE Tablename
ADD Attribute1

25
Q

How do you delete columns in a table?

A

ALTER TABLE Tablename
DROP COLUMN Attribute2

26
Q

How do you modify columns in a table?

A

ALTER TABLE Tablename
MODIFY COLUMN Attribute1

27
Q

How do you insert a new record into a table?

A

INSERT INTO (column1, column2)
VALUES (value1, value2)

28
Q

How do you update a record in a table?

A

UPDATE Tablename
SET column1 = value1, column2 = value2
WHERE columnX = value

29
Q

How do you delete a record from a database table?

A

DELETE FROM Tablename
WHERE columnX = value

30
Q

What is referential integrity?

A

Referential integrity is the process of ensuring data consistency.

31
Q

What is transaction processing?

A

A transaction is defined as a single operation executed on data

32
Q

What does the ACID acronym stand for?

A

Atomicity
Consistency
Isolation
Durability

33
Q

What is atomicity?

A

A transaction must be completed entirely or not at all

34
Q

What is consistency?

A

A transaction must maintain referential integrity

35
Q

What is isolation?

A

Simultaneous executions of transactions should lead to the same result

36
Q

What is durability?

A

Once a transaction has been executed it will remain so.

37
Q

What is the structure of the bus topology?

A

Every terminal is connected to a backbone cable which is connected to a terminator

38
Q

What is the structure of a star topology?

A

Star topologies use a central node (a switch) that directs data through a network

39
Q

What is the structure of a mesh topology?

A

In a mesh topology, every node is connected to every other node wirelessly

40
Q

What is the HTTP protocol?

A

HTTP stands for Hypertext Transfer Protocol is used for page rendering

41
Q

What is the TCP/IP protocol?

A

A networking tool used to route packets through the network

42
Q

What are the POP3 and IMAP protocols?

A

Used to access emails

43
Q

What is the FTP protocol?

A

Used to transmit files across a network.

44
Q

What are the different stages in the TCP/IP stack and how do they work?

A

Application layer: Decides what protocol needs to be used
Transport layer: Uses the TCP to create a link between the sender and recipient, splits up the data into packets
Network layer: Adds the senders and recipients IP addresses
Link layer: Adds the MAC address

45
Q

What is the difference between a LAN and a WAN?

A

A LAN is a local area network and works on a small geographical area unlike a WAN which is a large area network that works on a large geographical area.

46
Q

What is the DNS?

A

The Domain Name System is used to name and organise internet recourses

47
Q

What is HTML used for?

A

HTML is the language/script that web pages are written in. It is used for content, structure and order.

48
Q

What is CSS used for?

A

CSS is a language that is used to describe the style of a webpage

A level computer science (5 decks)

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