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Comp Sci 1 > 1.3 Exchanging data > Flashcards

1.3 Exchanging data Flashcards

1
Q

Why do we need to reduce the size of files

A

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

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2
Q

What are the two types of compression

A

lossy and lossless

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3
Q

What is lossless compression?

A

File size reduced without losing any original data

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4
Q

What is lossy compression?

A

Unneeded data permanently removed to lower file size. This data that is removed will be non noticable such as certain sound frequencies.

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5
Q

How does lossless compression work?

A

Records patterns in the data instead of the data instead to prevent recording redundant data

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6
Q

when should lossless compression be used

A

when no data can be lost for example a word document

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7
Q

examples of lossy compression

A

JPEG, MP3, MPEG

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8
Q

examples of lossless compression

A

ZIP
PNG
GIF

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9
Q

What are the two types of lossless compression

A

Run length encoding
Dictionary encoding

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10
Q

What is run length encoding?

A

Compression where conexcutive identical pieces of data are stored as one piece of data and a number representing length

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11
Q

What is dictionary compression

A

Spots regularly occuring data and stores it in a dictionary

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12
Q

How does dictionary compression reduce size

A

Repeated phrases are only stored once and are referenced with an identifier

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13
Q

What is encryption

A

The process of encoding a message so that it can be read only by the sender and intended recipient.

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14
Q

What is symmetric encryption?

A

An encryption method in which the same key is used to encrypt and decrypt a message

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15
Q

What is asymmetric encryption?

A

An encryption method in which two keys (one private, one public) are used to encrypt and decrypt a message. Such that someone with the public key can only encrypt and someone witht he private key can only decrpyt.

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16
Q

What is a one time pad

A

A one time key generated via random methods used for symmetric encryption

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17
Q

What is hashing

A

A one-way encryption an algorithm but no key

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18
Q

What are the uses of hashing

A

Storing passwords securly
Uniquely identify a file

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19
Q

What is a flat file database?

A

A database that consists of information on a single entity

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20
Q

What is an entity

A

A category of object, person, event or thing of interest about which data needs to be recorded

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21
Q

ther names for entities

A

Record, tuple

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22
Q

What is a relational database

A

Database that stores data points that are related to each other

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23
Q

What is a primary key

A

A field (or group of fields) that uniquely identifies a given entity in a table

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24
Q

What is a secondary key

A

Another field that can be used to identify an entity in a table

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25
Q

What is a foreign key?

A

A primary key of one table that appears as an attribute in another table and acts to provide a logical relationship between the two tables

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26
Q

How to write an entity description

A

EntityName(__PrimaryKey__, foreignKey, secondaryKey1, secondaryKey2)

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27
Q

What is a composite primary key?

A

A key made up of two primary keys from different tables

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28
Q

What is a one to one relationship

A

One entity is related to another single entity

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29
Q

What is a one-to-many relationship?

A

One entity is related to many entities

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30
Q

What is a many-to-many relationship?

A

Many entities a re related to many other entities

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31
Q

Diagram for one to one

A

Straight line between entities

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32
Q

Diagram for one to many

A

One ended 3 pronged pitch fork

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33
Q

Diagram for many to many

A

many
Two ended 3 pronged pitchfork

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34
Q

What are some manual methods of capturing data

A

Forms or surveys

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35
Q

What are some automatic methods of capturing data

A

Smart card readings
Barcode readers
Scanners
Optical character recognition
Optical mark recognition
Magnetic ink character regonition
Sensors

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36
Q

How can data be transferred to a databse

A

Automatically using DBMS software
By typing it in using a customised format
Importing from a spreadsheet or file
Using an EDI (Electronic Data Ingterchange)

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37
Q

What is an EDI

A

Computer to computer exchange of documents such as purchase orders
All documents must be in standard format

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38
Q

How do we select data in a database

A

Use SQL or similar to query data bases

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39
Q

What is database normalization

A

Process used to come up with the best possible design for a database
It avoids data duplication and inconsistency.

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40
Q

When is a database in first normal form

A

Contains no repeating attributes
All attributes must be atomic

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41
Q

When is a database in second normal form

A

It is in first normal form
It contains no partial dependencies

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42
Q

When is a database in third normal form

A

In second normal form
Contains no non key dependencies

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43
Q

Why is it important to be in third normal form

A

Easier to maintain data as integrity is preserved, so wen one piece of data is changed other instances of it a re changed

Searches are faster and less storage space is used due to no duplication of data

Easy to update data, due to fields only having to be added to one table as well as necessary data not being able to be deleted without being replaced

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44
Q

Example table creation sql

A

CREATE TABLE tblProduct
(
ProductID CHAR(4) NOT NULL PRIMARY KEY,
Description VARCHAR(20) NOT NULL,
Price CURRENCY
)

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45
Q

Alter table examples sql

A

ALTER TABLE tblProduct
ADD QtyInStock INTEGER
DROP QtyInStock
MODIFY COLUMN Description VARCHAR (30) NOT NULL

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46
Q

Linked table example sql

A

CREATE TABLE ProductComponent
(
FOREIGN KEY ProductID REFERENCES Product(ProductID),
FOREIGN KEY CompID REFERENCES Component(CompID),
PRIMARY KEY (ProductID, CompID) )

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47
Q

Insert into example sql

A

INSERT INTO Product (ProductID, Description, Price),
VALUES (“A345”, “Pink Rabbit”, 7.50)

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48
Q

Update example sql

A

UPDATE Product,
SET Description = “Blue Rabbit”, Price = 8.25,
WHERE ProductID = “A345”

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49
Q

Delete example sql

A

DELETE FROM Product
WHERE ProductID = “A345”

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50
Q

What is the default order for ORDER BY sql

A

Ascending

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51
Q

Select example sql

A

SELECT productID, productName, subject, price
FROM tblProduct
WHERE level = 4
ORDER BY productName

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52
Q

Between example sql

A

WHERE price BETWEEN 5.00 AND 10.00

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53
Q

In example sql

A

WHERE subject IN (‘Computing’, ‘Maths’)

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54
Q

LIKE example sql

A

WHERE subject LIKE “Comp*”

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55
Q

Selecting from multiple tables example sql

A

SELECT tblCustomer.custID, surname, tblProduct.productID, productName
FROM tblCustomer, tblProduct, tblSubscription
WHERE tblSubscription.custID = tblCustomer.custID AND tblSubscription.productID = tblProduct.productID

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56
Q

Join example sql

A

SELECT tblPlayer.surname, tblPlayer.firstname, tblTeam.teamName
FROM tblTeam, tblPlayer
JOIN tblPlayer
ON tblTeam.teamID = tblPlayer.teamID
WHERE team.teamName = “Binham”

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57
Q

What is transaction processing

A

The processing of several operations as part of a transaction (a single logical operation)

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58
Q

What is referential integrity

A

No foreign key in one table can reference a non existent record in a related table

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59
Q

Transaction processing example

A

Customer makes order:
may consist of several order line all of which must be processed
the quantity of each product adjusted on the stock fill
credit card details checked
payment accepted or rejected

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60
Q

What does ACID stand for?

A

Atomicity, Consistency, Isolation, Durability

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61
Q

What is ACID for

A

Ensures that the integrity of the database is maintained under all circumstances
It guarantees that transactions are processed reliably

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62
Q

What is Atomicity in ACID?

A

All or nothing principle

This property requires that a transaction is processed in its entirety or not at all

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63
Q

What is consistency in ACID

A

This property ensures that no transaction can violate any of the defined validation rules

Referential integrity, specified when the database is set up, will always be upheld

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64
Q

What is isolation in ACID?

A

Ensures that concurrent execution (at the same time) of transactions leads to the same result as if transactions were processed one after the other

65
Q

What is durability in ACID

A

This ensures that once a transaction has been committed, it will remain so, even in the event of a power cut
As each part of a transaction is completed, it is held in a buffer on disk until all elements of the transaction are completed
Only then will the changes to the database tables be made

66
Q

What is a potential problem with multi user databases

A

Simultaneous accessing of records may cause updates to the database to be lost

67
Q

What is record locking

A

Record locking prevents simultaneous access to objects in a database in order to prevent updates being lost or inconsistencies in the data arising

68
Q

What is the problem with record locking

A

If two users are attempting to update two records, a situation can arise in which neither can proceed, known as deadlock

69
Q

What is serialisation

A

ensures that transactions do not overlap in time and therefore cannot interfere with each other or lead to updates being lost

70
Q

What are the two types of serialisation

A

Timestamp ordering
Commitment ordering

71
Q

How does timestamp ordering work

A

Every object in the database has a read timestamp and a write timestamp
These are updated whenever an object is read
or written
When a user tries to save an update, if the read timestamp is not the same as it was when they started the transaction, the transaction fails

72
Q

What is commitment ordering

A

ensures that no transactions are lost if two clients are simultaneously trying to update a record
Transactions are ordered in terms of their dependencies on one another as well as the time they were initiated

73
Q

What is redundancy?

A

Having backups for when the main system goes down so everything continues to work as normal

74
Q

Example of redundancy

A

Duplicate hardware, located in different geographical areas, mirrors every transaction that takes place on the main system

75
Q

What is the internet

A

A network of inter connected networks

76
Q

What is the world wide web

A

A collection of resources accessed via the internet

77
Q

What is the backbone of the internet

A

The set of dedicated connections that connect several large networks at various points on the globe

78
Q

What is an IP address?

A

a unique string of numbers separated by periods that identifies each computer using the Internet Protocol to communicate over a network.

79
Q

What is a URL

A

specifies the means of accessing a resource across a network and its location, is linked to an IP address

80
Q

What is a DNS

A

The Domain Name System (DNS) converts domain names or host names into IP addresses.

Instead of having to remember a host’s IP address, DNS allows you to use a friendly name to access the host. For example, it is easier to remember http://www.cisco.com than 198.133.219.25.

81
Q

Why are URLs and DNSs so important

A

Instead of having to remember a host’s IP address, DNS allows you to use a friendly name to access the host.

82
Q

How might an IP address be resolves

A

1.Asks for bbc.co.uk
2.Local DNS doesnt know, refers to root DNS
3.Root DNS knows where .uk server is
4..uk server finds .co serveer
5..co server finds BBC server and resolves IP address

83
Q

What is A LAN

A

Local Area Network: two or more computers connected together within a small geographical area, for example confined to one building or site

84
Q

What is a WAN

A

Wide area network Systems of LANs that are connected over a large geographical distance

85
Q

What is a network topology

A

A network topology is the arrangement of the various computing devices which make up a computer network

86
Q

What is a bus topology

A

An arrangement where nodes are connected in a daisy chain by a single central communications channel

87
Q

What is a star topology?

A

An arrangement where a central node or hub provides a common connection point for all other nodes

88
Q

What hardware might be used in a star network as the central node

A

Switch: sends each communication to the specific computer it is intended for

89
Q

Advantages of a bus network

A

Inexpensive to set up
Devices can easily be added
Good for small networks

90
Q

Disadvantages of a bus network

A

Main cable is a point of failure
Limited cable length
Performance degrades with heavy use, owing to data “collisions”
Poor security

91
Q

Advantages of a star network

A

Easy to isolate problems
Good performance
More secure if a switch is used as data is sent only to the recipient

92
Q

Disadvantages of a star network

A

Can be expensive to set up because of the length of cable required
Central device is point of failure

93
Q

What is physical topology

A

The physical topology of a network defines how the devices are physically connected

94
Q

What is a logical topology?

A

The logical topology defines how the devices communicate across the physical topologies

95
Q

What is a wifi newtork

A

One that allows devices to connect to it wirelesses

96
Q

What is wireless hardware

A

Wireless Network Interface Card
Wireless access point connected to a router, connected to a modem

97
Q

What is circuit switching

A

Circuit switching involves creating a communication connection between two endpoints for the duration of a phone call or transfer of data

98
Q

Why is circuit switching unfeasible for the internet

A

Too many devices to be able to make manual connections between

99
Q

What are packets

A

Small chunks of one whole data sent individually throughout the web on their own path

100
Q

What is the advantage of packets

A

Means large pieces of data are split up so one connection isnt taken up completely for a long time

101
Q

What is latency

A

Latency is the length of time it takes to receive a response back after receiving a packet

102
Q

What is packet switching

A

The packets across multiple, not necessarily perfect routes to reach a destination

103
Q

What is a router

A

A piece of hardware that forwards packets based on IP address

104
Q

What is a transfer between routers called

A

A hop

105
Q

How does routing work

A

Each router stores data about the available routes to the destination node
Looks up the destination IP address in its routing table to find the best router to forward the packet to
Routers continue to forward the packet until it reaches its destination node

106
Q

What is a packet made of

A

Sender IP address
Receiver IP address
Protocol
Packet number
Data
Checksum

107
Q

What is a protocol

A

A set of rules, or a formal description, of the format of a digital transmission

108
Q

What is a gateway

A

Connects one network to another And converts data to required protocol

109
Q

Why are protocols important for networking?

A

Defines the rules of communication so data can be transferred and meaningfully decoded such that we can communicate over a network

110
Q

What is the TCP/IP protocol stack

A

A set of rules used in turn, to format a message so it can be sent over a network

111
Q

What are the layers in the TCP/IP stack

A

Application
Transport
Network
Link

112
Q

What happens in the application layer while transmitting

A

Determines the format of the data to be transmitted

113
Q

What happens in the application layer while receiving

A

Receives full data and displays or stores it

114
Q

What happens in the transport layer when sending

A

Establishes an end‐to‐end connection with the recipient computer
Splits data into packets

115
Q

What happens in the transport layer when receiving

A

Rearranges packets into full data

116
Q

What happens in the internet layer when sending

A

Addresses packets with recipient and sender

117
Q

What happens in the internet layer when receiving

A

Removes addresses of recipient and sender and pass up to transport layer

118
Q

What happens in the link layer when sending

A

Addresses packets with mac addresses of next hop

119
Q

What happens in the link layer when receiving

A

Receives packets and strips mac address

120
Q

Explain why TCP and IP are able to work with different application protocols and different network media

A

Anything above or below these protocols is separate and does not interact with them

121
Q

What is a MAC

A

Media Access Control address: uniquely identifies a physical device with a Network Interface Card

122
Q

What is a port

A

The logical connection point for the transmission of information packets.
Used to alert a specific application to deal with data sent to a computer

123
Q

What is FTP

A

File Transfer Protocol is an application level protocol used to move files across a network

124
Q

What is SMTP

A

Simple Mail Transfer Protocol, Used to send emails and forward them between mail servers to their destination

125
Q

What is POP3?

A

Post Office Protocol 3, Downloads email stored on a remote server to a local client (removed after download)

126
Q

What is IMAP

A

Internet Message Access Protocol, Manages emails on a sever so multiple clients can access the same email account in synchronicity

127
Q

What is a firewall

A

A firewall is either software or hardware that controls access to and from a network
Numbered doors called ports are opened so that only certain traffic is allowed to pass through

128
Q

What is packet filtering

A

Packets of data are inspected by the firewall to check which port they are attempting to access
If this traffic is to be allowed through, the port must be opened for the duration of the connection, otherwise the firewall will automatically reject it

129
Q

What is a proxy server?

A

A proxy server makes a web request on behalf of your own computer, hiding the true request IP addresses from the recipient

130
Q

What are the functions of a proxy server

A

Enables anonymous surfing
Can be used to filter undesirable online content
Logs user data with their requests
Provides a cache of previously visited sites to speed access

131
Q

What is a worm

A

A self-replicating program or algorithm that consumes system resources.

132
Q

What is a trojan

A

malicious software programs that masquerade as innocuous or useful applications

133
Q

What is phishing

A

using email to manipulate a victim into visiting a fake website and giving away personal information

134
Q

What can help prevent malware and attacks

A

Guarding against buffer overflow attack
Guarding against SQL injection attack
Use of strong passwords for login credentials
Two-factor authentication
Use of access rights (file system permissions)

135
Q

What is buffer overflow

A

Buffer overflow occurs when a program accidentally writes data to a location too small to handle it
As a result the overflowed data (written to location #3 below) may end up in a neighbouring instruction space, causing a system to crash

136
Q

What is SQL injection?

A

A malicious user can enter SQL commands via online database forms to change the processing

137
Q

How can we monitor a network for safety

A

Packet sniffers
User access logs

138
Q

What is a client server model

A

A network model consists of two parts: the client and the server
The client accesses data, services and files from the server
The client initiates communication to the server
The server waits for requests from clients

139
Q

What is a peer-to-peer network?

A

A network in which each computer has both server and client capabilities.

140
Q

What are the characteristics of client server

A

User IDs, passwords and access levels centrally controlled
Used in many small, medium-size and large organisations
Can be expensive to set up and to manage
Backup is centralised and usually automated
No access to other users’ files

141
Q

What are the characteristics of peer to peer

A

Files and programs stored on individual computers
Suitable for a home computer network
Cheap to set up and maintain
Each computer on the network can act as both client and server
Can be used for sharing of music and streaming coverage of live events

142
Q

What is client processing

A

Data is processed before it is sent to a server by the client

143
Q

What is Server processing

A

Data is processed when it is received by the server from the user

144
Q

What is an API

A

An application programming interface, a set of tools that can be used for building software applications

145
Q

What is a search engine

A

systems that locate resources (web pages, files, pictures) on the World Wide Web

146
Q

What is a search engine index

A

A record of the resources located on the world wide web

147
Q

How is an index created

A

Using a web crawler

148
Q

Why is an index useful

A

Collecting all web pages in one place is very useful to the user as they can more easily find the web pages they want without having to search through many pages to find what they want.

149
Q

How does a web crawler work

A

Follows every link on a website and does the same for each link in order to index as many web pages as possible

150
Q

What are meta tags

A

Describe the content of the web page

151
Q

How are meta tags used in the search process

A

Sites with relevant content in metatags will be more highly recommended by the search engine as it is more likely for the user to want to go to that site

152
Q

What is pagerank

A

Algorithm to determine which web pages should be shown when a user searches somethink

153
Q

What affects a web pages page rank

A

Incoming links
Outgoing links
Meta tags

154
Q

When should server side processing be used

A

Database queries
Encoding data to readable HTML
Updating the database
Calculations

155
Q

What are the benefits of server side processing

A

Provides further validation
Keeps data owned by organisations secure

156
Q

What should client side processing be used for

A

Initial validation
Web page interactivity
Manipulating interface elements
Applying styles (CSS)

157
Q

What are the benefits of client side processing

A

Reduces the load on the server
Reduces the amount of web traffic

158
Q
A

Comp Sci 1 (6 decks)

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