unit 4

Question 1

what is compression?

Answer 1

reducing the size of a file

Question 2

what is lossy compression?

Answer 2

reducing file size when some data is discarded/removed

Question 3

what is lossless compression?

Answer 3

reducing file size and all original data is kept

Question 4

what are the benefits of lossy compression?

Answer 4

• greatly reduced file sizes
  suitable for media streaming where some data loss is acceptable

Question 5

what are the benefits of lossless compression?

Answer 5

maintains original data
best for text and data thar require integrity like documents

Question 6

what are the drawbacks of lossy compression?

Answer 6

irreversible loss of data quality
not suitable for text or archival storage

Question 7

what are the drawbacks of lossless compression?

Answer 7

larger file sizes than lossy
requires high bandwidth when streaming

Question 8

what is run length encoding?

Answer 8

a form of data compression that condenses identical elements into s single value with a count

Question 9

where is RLE used?

Answer 9

in bitmap images to compress sequences of the same colour

Question 10

what is dictionary coding?

Answer 10

a compression which replaces recurring sequences with shorter, unique codes
a dictionary is compiled to map original sequences to special codes

Question 11

what is encryption?

Answer 11

process of converting readable data into an unreadable format to provide security

Question 12

what is the purpose of keys in encryption?

Answer 12

they are specialised programs designed to scramble or unscramble data

Question 13

how does symmetric encryption work?

Answer 13

sender uses a key to encrypt the data before transmission
the receiver uses the same key to decrypt the data

Question 14

what are the benefits of symmetric encryption?

Answer 14

faster, making it ideal for encrypting large amounts of data

Question 15

what are the drawbacks of symmetric encryption?

Answer 15

challenge of securely sharing the key, can be intercepted

Question 16

how does asymmetric encryption work?

Answer 16

uses 2 keys, public one for encryption, private one for decryption
receivers openly share their public key and senders use this public key to encrypt the data
receiver’s private key is the only key that can decrypt the data

Question 17

what are the benefits of asymmetric encryption?

Answer 17

secure, best for confidential transmissions
suitable for smaller data

Question 18

what is hashing?

Answer 18

the method to convert any data into a fixed-size string of characters

Question 19

what is the general rule for hashing?

Answer 19

same input always produces same hash

Question 20

how is hashing used in password storage?

Answer 20

the password a user provides is hashed, it is then stored in a database
when they log in they enter their password and the system hashed their input
it is then compared to the stored hash in the database

Question 21

what are the benefits of hashing passwords?

Answer 21

adds extra layer of security
if database is compromised, the attacker can’t use the hashed passwords
users’ raw passwords are not exposed

Question 22

how is hashing used in data retrieval?

Question 23

how is data integrity linked to hashing?

Answer 23

when data is transferred, susceptible to loss of packets or interference, so if hashes are compared it allows the system to verify the integrity of the data

Question 24

what is a database?

Answer 24

an organised collection of data which allows easy storage and retrieval of information

Question 25

what is a field?

Answer 25

a single piece of data in a record

Question 26

what is a record?

Answer 26

a group of related fields representing one data entry

Question 27

what is a table?

Answer 27

a collection of records with a similar structure

Question 28

what is a primary key?

Answer 28

a unique identifier for each record in a table

Question 29

what is a compound primary key?

Answer 29

a combination of 2 or more fields that is unique for all records

Question 30

what is a foreign key?

Answer 30

a field in a table that refers to the primary key of another table used to link tables

Question 31

what is a secondary key?

Answer 31

a field that is indexed for faster searching

Question 32

what is a DBMS?

Answer 32

software used to manage databases

Question 33

what is indexing?

Answer 33

a technique used to speed up data retrieval in a database which indexes a field

Question 34

what is a flat file database?

Answer 34

a database that stores all data in a single table

Question 35

what is a flat file suitable for?

Answer 35

simple and easy to understand, good for small uncomplicated datasets

Question 36

what are the drawbacks of a flat file?

Answer 36

leads to data redundancy, inefficient storage and integrity issues

Question 37

what is a relational database?

Answer 37

a database that organises data into multiple tables with relationships established between the tables

Question 38

what are the advantages of a relational database?

Answer 38

uses key to reduce redundant data and improve integrity

Question 39

what is normalisation?

Answer 39

the process of organising a database to reduce data duplication and improve data accuracy and consistency

Question 40

what is 1NF?

Answer 40

contains atomic values (each column has single values) no repeating groups unique column names have a primary key

Question 41

what is 2NF?

Answer 41

fulfil all 1NF requirements have no partial dependencies full functional dependency

Question 42

what are no partial dependencies?

Answer 42

non-prime attributes must not depend on only part of the primary key separate tables should be created for partially dependent attributes

Question 43

what is a one time pad?

Answer 43

one-time pad must be truly random, generated from a physical and unpredictable phenomenon

Question 44

what are transitive dependencies?

Answer 44

when a non key attribute depends on another non key attribute rather than depending directly on the primary key

Question 45

how do you delete a field from a table?

Answer 45

DELETE FROM table WHERE FIELD = ...

Question 46

how do you create a join in a database?

Answer 46

INNER JOINE Table ON Table.ID = Table2.ID

Question 47

what is transaction processing?

Answer 47

where a task is completed to ensure that a database is updated and data is consistent ensures integrity

Question 48

what does the A in ACID stand for?

Answer 48

atomicity

Question 49

what does the C in ACID stand for?

Answer 49

consistency

Question 50

what does the I in ACID stand for?

Answer 50

isolation

Question 51

what does the D in ACID stand for?

Answer 51

durability

Question 52

what is record locking?

Answer 52

a method used to prevent data in a record being edited by 2 separate users simultaneously record locked by first user then unlocked when first user has finished transaction

Question 53

what does the commit transaction mean?

Answer 53

where results of the transaction are permanently stored if all operations are successful

Question 54

what does the rollback transaction mean?

Answer 54

an explicit command where the transaction changes are rolled back to original database if transactions were not sucessful

Question 55

explain the cascading update of fields techniques

Question 56

define data integrity

Answer 56

the correctness and consistency of data in a database

Question 57

define referential integrity

Answer 57

ensures that relationships between tables remain consistent a foreign key matches a primary key