class revision

Question 1

difference between redundant data and data redundancy

Answer 1

• redundant data is BAD(repeated data in the database)
• data redundancy is when copies of the database are made so they can be used in case something happens

Question 2

when does a datanase have RI (2)

Answer 2

• relationships are consistent
• each foreign key links to an existing primary key

Question 3

what is a foreign key

Answer 3

a key in another table which references the primary key

Question 4

what is a constraint in a database

Answer 4

a set of ules set by the programmer such as defining the primary key and the foreign key.

Question 5

what enforces data integrity

Answer 5

ACID

Question 6

what happens when data moves down layers

Answer 6

it is further encapsulated (headers and addresses are added)

Question 7

what performance modelling

Answer 7

when simulations are produced to model situations before implementing these into the real world

Question 8

what are the advantages to caching(2)

Answer 8

• faster response times as data doesn’t need to be read from disk
• reduces the load on a system(fewer data access movements)

Question 9

what are the disadvantages to caching(2)

Answer 9

• very hard to program and apply successfully
• if the wrong data is cached the program could end up running slower

Question 10

what are the 4 chategories of development methodologies

Answer 10

• linear
• ## iterative
• predictive(documebt focused)
• adaptive(code focused)

Question 11

what is a global variable

Answer 11

a variable which is defined in the main program

Question 12

what is a local variable

Answer 12

a variable which is defined in a procedure/function

Question 13

how does ByValue work

Answer 13

a copy of the variable’s data is passed into the subroutine

Question 14

how does ByReference work

Answer 14

a pointer to the variable’s
memory location is passed

Question 15

what is the purpose of the address bus

Answer 15

to transmit the address of data to be read from or written to RAM

Question 16

where is the data stored when the address bus reads from it

Answer 16

in the MAR

Question 17

what is the purpose of the data bus

Answer 17

to transmit data between CPU and RAM

Question 18

what are the protocols involved in the application layer

Answer 18

HTTP and DNS

Question 19

what is the role of the HTTP

Answer 19

sends requests to webpages

Question 20

what is the protocol involved in the transport layer and what does it do

Answer 20

TCP, creates a reliable connection between the nodes and the server

Question 21

what happens in the transport layer

Answer 21

• headers and port numbers are added to data packets
• packets are reordered as they arrive at the destination

Question 22

what protocol is involved in the internet layer

Answer 22

IP

Question 23

what happens in the internet layer

Answer 23

• routers use IP addresses to direct data packets across networks
• headers are added to packets

Question 24

what is the protocol involved in the link layer

Answer 24

ETHERNET

Question 25

what happens in the link layer

Answer 25

data packets travel through cables

Question 26

what are the 3 steps to packets switching

Answer 26

1. data is split into equal sized blocks, called packets, each packet has a header of information(destination address)
2. each packet is placed on the network and each packet may take a different route
3. packets are reordered at the destination

Question 27

what does the TCP protocol stand for

Answer 27

Transmission Control Protocol

Question 28

3 properties of a good hashing algorithm

Answer 28

• reduced chances of collisions
• even distribution
• fast execution

Question 29

what is linear probing

Answer 29

the value is placed in the next empty bucket(index)

Question 30

what is chaining

Answer 30

when each bucket in the in the hash table has its own linked list,that points to the next value added to that bucket

Question 31

what is the value in the index called when chainnig is used

Answer 31

pointer to memory location