1.3 Exchanging Data

Question 1

What is compression used for?

Answer 1

Used to reduce storage space, which is useful when sending an file via the internet as the longer the file the more time it takes to send.

Question 2

Pros of compression (both types)

Answer 2

Data sent more quickly
Less bandwidth used
Buffering less likely to occur
Less storage required

Question 3

What are the 2 types of compression?

Answer 3

Lossy and Lossless

Question 4

What is lossy compression?

Answer 4

Reduces file size while also removing some of its information

Question 5

what can lossy compression lead to in images and audio

Answer 5

could lead to a more pixelated image or less clear audio.

lower quality img/audio

Question 6

What is lossless compression?

Answer 6

Reduces file size withought losing any information. The original file can be recovered from the compressed version.

Question 7

How is lossless compression done

Answer 7

Groups of repeating data found and recorded along with the number of repetitions

Question 8

Which is more effective, lossy or lossless

Answer 8

Lossy (most times) when trying to reduce file siles

Question 9

What is lossy compression suitable for?

Answer 9

Images audio and video

Question 10

What is lossless compression suitable for?

Answer 10

Executable files and documents

Question 11

Why should lossless be used for texts

Answer 11

Lossless is the only option for files such as text files or executable programs, where any loss of data would destroy their functionality.

Question 12

What is encryption?

Answer 12

The process of encoding plaintext to ciphertext so it can only be read by the sender and the intended recipient.

Question 13

What is symmetric encryption?

Answer 13

This is when Both parties use a single key to both encrypt and decrypt a message.

Question 14

What is necessary for systematic encryption?

Answer 14

Both parties have the key to encrypt and decrypt the message

Question 15

What is the problem to systematic encryption?

Answer 15

1.Interception of the key
2.Duplication of the key production process

Question 16

What is a more safe alternative to systematic encryption?

Answer 16

asymmetric encryption

Question 17

What is different in asymmetric encryption?

Answer 17

We use 2 different keys, the first key to encrypt it and the second key to decrypt.

Question 18

Why is asymmetric encryption good

Answer 18

1.No one else will be able to read the message
2.Can make sure the message is authentic

Question 19

What are the 2 keys called in asymmetric encryption?

Answer 19

Key pairs.

Question 20

For asymmetric encryption what do we have to do to one of our key?

Answer 20

Make one private key and make one public.

Question 21

If we want to send an asymmetric encrypted message to another person what would we do 3 steps?

Answer 21

1.Exchange/Take their public key
2.Use their public key to encrypt the message you want to send and send it to them.
3.They would use their private key to decrypt it.

Question 22

If we want to send the most secure asymmetric encrypted message to another person what would we do 3 steps?

Answer 22

1.Combine your private key with their public key.(Combined encryption key)
2.Then use this combined key to encrypt the message and send it to them
3.To decrypt the message they would use their own private key and your public key

Question 23

What is it called when you combined your private key and their public key?

Answer 23

Combined encryption key

Question 24

What is a database?

Answer 24

An organised collection of data

Question 25

When looking at a database what is it you see?

Answer 25

1.Table 2.Records 3.Fields

Question 26

What is a flat file Database?

Answer 26

A database that only holds a single table Represented using a data dictionary

Question 27

What are the 5 benefits of flat file Database?

Answer 27

1.Simple 2.Quick to setup 3.Easy maintenance 4. Easy to Use 5. Cheap

Question 28

What is 3 disadvantage of flat file database?

Answer 28

1.Take up unnecessary space 2.Slow to query 3.Difficult to maintain if too much data in it

Question 29

What is a relational database?

Answer 29

A database with multiple tables linked together

Question 30

What is the primary key?

Answer 30

Unique Identifier for each record

Question 31

What is an entity

Answer 31

A category of a person, place, thing or concept about which data can be collected.

Question 32

What is an attribute

Answer 32

the facts, details or characteristics of an entity

Question 33

Whats a composite key

Answer 33

A primary key with multiple fields

Question 34

What do foreign key have to reference to in another table

Answer 34

Have to reference the primary key of the other table.

Question 35

What is a index in databases?

Answer 35

A database automatically has an index of primary keys so that specific primary keys can be located quickly

Question 36

5 rules for First Normal form?

Answer 36

1.All field name unique 2.Values in fields should be the same type of data. 3.Values in field should be atomic. 4.No two records identical 5.Each table needs a primary key

Question 37

What is a composite key?

Answer 37

Combination of two or more field in table used to uniquely identify each record.

Question 38

2 rules for Second Normal form?

Answer 38

1.Data already in 1NF. 2.Any partial dependencies are removed

Question 39

2 rules for 3NF?

Answer 39

1.In second normal form 2.All fields must depend on the primary key and nothing else but the primary key./No transitive dependencies

Question 40

What is a hash?

Answer 40

The result generated by applying an algorithm to a value.

Question 41

What is the benefit of using a hash function?

Answer 41

Hash functions are one way. If someone gains access to the hashed value they cant see the real one

Question 42

What is not allowed in 3NF?

Answer 42

Many to many relationships.

Question 43

What is an advantage of indexing and what is a disadvantage?

Answer 43

1.Easy access to what you have index 2.Takes more space in database.

Question 44

What is special about hash functions?

Answer 44

They are one way.

Question 45

What are the 2 serialisations techniques?

Answer 45

Timestamp ordering Commitment ordering

Question 46

What do serialisations do?

Answer 46

Serialisation ensures that transactions do not overlap in time and therefore cannot interfere with each other.