A-Level Computer Science Flashcards
(442 cards)
1
Q
What is the SDLC?
A
A project management model that allows the project to be on time and in budget
2
Q
What does SDLC stand for?
A
System Development Life Cycle
3
Q
What does the SDLC do?
A
Defines the stages involved in bringing a project from start to end
4
Q
How many stages are on the SDLC?
A
7
5
Q
How is each stage planned and carried out?
A
They are planned and carried out in a time frame, depending on the size of a problem
6
Q
What happens if the software/hardware is out of date?
A
If the software/hardware is out of date, the system analyst may create an entire new system
7
Q
What are the 7 stages of the SDLC?
A
- Feasibility Study
- Analysis
- Design
- Create
- Test
- Changeover
- Maintenence
8
Q
What happens in the Feasibility Study stage of the SDLC?
A
Understand the problem the client has given you
9
Q
What happens at the Analysis stage of the SDLC?
A
Analyse the problem given to you, breaking it down
10
Q
What happens at the Design stage of the SDLC?
A
Produce designs for the problem
11
Q
What happens at the Create stage of the SDLC?
A
Programming the design
12
Q
What happens at the Test stage of the SDLC?
A
Make sure the code is bug free
13
Q
What happens at the Changeover stage of the SDLC?
A
The code is installed into the new system
14
Q
What happens at the Maintenence stage of the SDLC?
A
Maintaining the code making sure there are no errors
15
Q
What are methodologies/system approaches?
A
Methods to ensure the project is on time and in budget
16
Q
What are the 2 main methodologies?
A
Agile, Waterfall
17
Q
What are some similarities and differences between the 2 methodologies?
A
Both follow the same 7 stages of the SDLC, however they have different approaches
18
Q
What are some features of the Waterfall methodologies?
A
Fixed time and budget- no flexibility
Problems can be difficult and timely
Previous stage MUST be completed before going to next
Large amounts of documentation
Rigid
Needs to be clear on its responsibility
Suited for small projects
19
Q
What are some features of the Agile methodologies?
A
Adaptable, focuses on customer’s needs
Several variations of Agile (Kanban, Scrum, Extreme Programming/XP)
Allows for feedback
Flexible
Suited for indecisive client
Can go between stages- does NOT have to be in order
Looping back may take time
Rapid method
Lack of emphasis on necessary designing and feedback
20
Q
What are some features of the Feasibility Study?
A
Takes months
Has to decide if current hardware is good to use or should start from scratch
Has to decide what type of project it is
21
Q
What is the acronym for the aspects Feasibility Study?
A
S- Schedule Feasibility
T- Technical Feasibility
O-Operational Feasibility
L-Legal Feasibility
E-Economic Feasibility
22
Q
What would be considered under Schedule Feasibility?
A
Can it be done in a reasonable time?
23
Q
What should be considered under Technical Feasibility?
A
Use current hardware or start from scratch?
24
Q
What should be considered under Operational Feasibility?
A
Will there be extra work? Is anyone going to need to be trained?
25
What should be considered under Legal Feasibility?
Will there be any legal issues?
26
What should be considered under Economic Feasibility?
How much will it cost? Is it worth spending the money?
27
What is the Analysis stage of the SDLC?
Finding out exactly what needs to be done to solve the problem using various fact finding methods
28
What are the 4 main fact finding methods?
Observation
Questionnaire
Document Collecting
Interview
29
What is Observation?
The process of gaining data by observing events and behaviour in a systematic manner
30
Who is observed during an Observation study?
The End Users
31
What are some advantages and disadvantages of Observation?
Advantages: Accurate, used on End Users
Disadvantages: Time consuming, behaviour may change
32
What is Questionnaire?
Creating valid and reliable questions that relate to the assessment objectives
33
What are some advantages and disadvantages of Questionnaire?
Advantages: Cheap, accurate (used on End Users)
Disadvantages: May lack responses, may be time consuming
34
What is Document Collecting?
Collecting a set of documents that specify what the client needs
35
What are some advantages and disadvantages of Document Collecting?
Advantages: Easily shared with others working on the project, low cost
Disadvantages: May contain errors, might be time consuming to go through
36
What is Interview?
A one-on-one with the client to specify what they need
37
What are some advantages and disadvantages of Interviews?
Advantages: Personalised, allows the client to be specific
Disadvantages: Time consuming, expensive
38
What is Decomposition?
Breaks down a large problem into several smaller problems that are easier to tackle and work with
39
What is Abstarction?
Removes all specific details and only keeps the facts needed. Creates a general idea of what the problem is and how to solve it
40
How might a System Analyst represent data?
A Data Flow Diagram (DFD)
41
What does a D(ata) F(low) D(iagram) show?
The input and output of data, what processes were carried out and what data was sorted
42
What does this symbol represent?:
---------------->
Flow of Data
43
What does this symbol represent?:
-----------------------
|
-----------------------
Storage
44
What does the phone symbol represent?
| |
Process
45
What does this represent?:
----------
| |
----------
| |
----------
External Entities
46
What are the 2 programming languages?
Low level languages, High level languages
47
What is a Low level language?
Low level languages have certain code words instead of long Binary numbers. Converted into machine code
48
What is Machine Code?
The language the Computer understands
49
What is a High level language?
Coded in a way so humans can understand it. Close to the human language. Also converts into machine code
50
Which converts faster, and why?: Low level languages, High level languages
Low level languages convert faster than high level languages because Low level languages converts into High level languages
51
What is a Procedural Language?
Structured in sequence and order. It is an example of a Programming paradigm.
52
What are some features of Procedural Languages
Uses step-by-step instructions
Uses functions and procedures
Obeys instructions
Carries out actions/calculations
Programmer defines precisely each step when performing a task
Very versatile (covers a lot of the basic programming needs)
Many programmers learn to code with Procedural Languages
53
What is a Programming Paradigm?
A fundamental approach and structure of a programming language. Can be thought of as different categories of High level languages
54
What is the Programming Stage?
The Programmer replicates the design so you can have it on a computer
55
What's the 5th stage of the SDLC?
Testing Stage
56
What is the Testing Stage?
The System Analyst ensures the system is useable and has no bugs before the program is installed
57
Why is the Testing Stage important?
To make sure the program is bug free
58
Why is a program being bug free important?
If there are many bugs, the system can keep crashing
Can be harmful to company, may lose customers
59
What are the 3 types of testing?
Alpha, Beta, User Acceptance
60
What is Alpha testing?
Still at development stage and is tested IN HOUSE
Changes may still be made to the system
Large companies use seperate software testing engineers
61
What is Beta testing?
Software is very close to completion
Given to users who have a general interest in the product
Used in ways software engineers don't consider
62
What is User Acceptance testing?
When users buy the final product/staff use the new system
Tested in the 'Real World'
Can still be updated to fix bugs or fix any weakpoints in the system
63
What is Continuity of Service?
Service offered by businesses has to be constantly offered. Can't have the service drop
64
What are the 4 types of changeover?
Direct changeover
Pilot changeover
Phased changeover
Parallel changeover
65
What is Direct changeover?
Turn off the old system, turn on the new system
66
What are some advantages of Direct changeover?
New system is available immediately
Easiest method of changeover
Cheapest method of changeover
Doesn't need multiple sets of data
67
What are some disadvantages of Direct changeover?
Riskiest method (if new system fails there is no other system to fall back on)
All data has to be moved to new system for old one to shut off
Period of downtime is created
Upheaval for staff who haven't used the new system
68
What does 'upheaval' mean?
Making you use something you aren't familiar with
69
What is Pilot changeover?
Some branches try the new system while the other branches keep the old system
70
What are some advantages of Pilot changeover?
Only a small part of the system is affected
Problems in the new system can be identified without affecting the whole company
Staff from the pilot branches can train other staff who haven't used the new system
71
What are some disadvantages of Pilot changeover?
Chosen branches experience same disadvantages as other branches for a 'direct changeover'
Staff on new system might find it hard to share data with staff on old system
Extra work for IT, have to manage 2 systems
72
What is Phased changeover?
The new system gets integrated with the old system, and the old system is slowly replaced by the new system
73
What are some advantages of Phased changeover?
Less risks of the system going wrong
Only effects one specific part of the system
Staff are introduced to system in small stages
74
What are some disadvantages of Phased changeover?
Can take a long period of time
Users asking for changes holds up next phase of installation
Difficult to integrate old and new system
75
What is Parallel changeover?
Old and new system run at the same time
Once the new system is okay, it can be changed
If new system fails, old one is there
76
What are some advantages of Parallel changeover?
Less risk than over methods- if the old system fails, the old one is still available
Less stress for staff, still have security of old system
Staff can take their time learning the new system
77
What are some disadvantages of Parallel changeover?
Time consuming- data has to be entered on 2 systems
One system becomes out of sync with the other
Maintaining multiple sets of data can lead to errors
Extra cost of running and maintaining 2 systems
78
What is Documentation?
Documents that are produced throughout the stages of the SDLC
Includes design documents, diagrams, requirement specifications and reports
79
Who are the documents in the interest of?
All documents are of interest to the development team
80
When and why are documents important?
Important in the development cycle
Important for customers and end users
81
What is a user guide?
Guides the user on how to use the system
Used as training
82
What are some features of a user guide?
Instillation guide
Glossary
Material must be suited for novices
Frequently Asked Questions (FAQs) that help with common problems (trouble shooting)
Reference manual
83
What is a Technical guide?
Designed to help IT literate users maintain and potentially improve the system
84
What are some features of a Technical guide?
Algorithmic designs (pseudocode, flowcharts)
Annotated code listings (that abide by coding standards set by the company)
Variable lists
Data dictionary
Configuration guide and options
85
What is maintenance?
Monitoring the system to make sure there are no bugs
86
What are some features of maintenance?
Rarely free
Expensive
Needs monitoring
Have to pay someone with experience
87
What are the 3 types of maintenance?
Corrective maintenance
Adaptive maintenance
Perfective maintenance
88
What is Corrective maintenance?
Finding bugs in the system
89
What is Adaptive maintenance?
Making changes to the system due to external influence
90
What is perfective maintenance?
Minor improvements to systems that have been around for a while
91
What is the name for planning for data loss?
Disaster Planning
92
How can data be destroyed?
Fire
Theft
Disk failure
Hacking
93
What is a backup?
Keeping a copy of software and data so they can be recovered should there be a loss
94
Why is regular backup crucial for organisations?
The data they have is more valuable than anything else
95
What are periodic backups?
Backing up data on a regular basis, can differ from person to person/business to business
96
Name the 3 main backup methods
SSD
The Cloud
USB
97
What are SSD's?
A storage medium that uses interconnected flash memories to store data without power
98
What are some advantages of SSD's?
Fast read-write time
Energy efficient
Compact
99
What are some disadvantages of SSD's?
Expensive
Less available
Read-write cycle concerns
100
What is The Cloud?
Storage medium that can be accessed by anyone with Wi-Fi
101
What are some advantages of The Cloud?
High speed
Reliable
Mobile
102
What are some disadvantages of The Cloud?
Security threats
Downtime
Lower Bandwidth
103
What is a USB?
Small storage medium that can be carried with you
104
What are some advantages of a USB?
Portable
Cheap
Secure
105
What are some disadvantages of a USB?
Risk of malware
Not durable
Used to steal information
106
What should every company have, in terms of backups?
Every company should have a Backup Policy
107
What is a backup?
The process of copying files from main storage to a seperate area
108
Why should the backup files always be tested?
So the backup data is ready for use should it be needed for use
109
Why are backups important?
If a file gets deleted, the backup file can be collected for use
110
What should the backup policy consider?
Where will the backup be stored?
What will the backup be stored on?
How often will the backup occur?
How long will the backup be kept?
111
What should be considered when planning a backup procedure?
Content and type (What will be backed up?)
Timing (When will the best time for a backup be?)
Frequency (How often will a backup occur?)
Backup media (Which media should be used for the backup?)
Location (Where will the backup be kept?)
Responsibility (Whose responsibility will it be to ensure the backups are kept?)
112
What is a full back up?
Copying all the files on the system to a seperate area
113
What type of business would use a full backup?
Small businesses that don't have a lot of data
114
What are some advantages of full backups?
Ultimate protection
System can be restored at any time
Most efficient system (If files haven't changed, the same files will be getting copied)
115
What are some disadvantages of full backups?
As business grows, the time to back up all the data will grow
If the backups get stolen, the thief has access to all the company's data
116
What is a differential backup?
Only backing up the files that have been changed since the last full backup
117
How does a differential backup compare to a full backup?
Faster than full backups
Data getting backed up grows until next full backup
More flexible, but unwieldly to do more than once a day
118
What is incremental backup?
Only backing up data that has been changed since the last incremental backup
119
What is recovery?
Taking the backup and copying the data to wherever the data is needed
120
What is an algorithm?
A list of instructions carried out in order
121
What is syntax?
The laws of the language that allow everything to run
122
What is a Syntax Error?
Breaking the laws of the language
123
What are some contemporary methods of HCI?
Voice inputs
Touch screen
Force feedback
Virtual reality
Augmented reality
124
How is interaction between humans and computers evolving?
Moving away from interfaces like keyboards and mice, to more tactile and intuitive methods
125
What is voice input?
Using the human voice to control computing systems
126
What is an advantage of voice input?
Useful for those who can't physically type
127
What is touch screen?
Allows for gestures- such as swipes- to interact with computing systems
128
What is force/haptic feedback?
Physical sense that tells you an action has occurred through vibrations
129
What is virtual reality?
User is transported to a different world using technology
130
What is one effect of virtual reality?
Takes over the user's senses
131
What is augmented reality?
Lays digital information over the real world
132
What is needed to use AR (augmented reality)?
Special lense/phone camera
133
What does HCI stand for?
Human Computer Interface
134
What is Design Validation?
A check done after the new system has been designed to ensure the design meets original specifications set during the analysis stage
135
Why is Design Validation important?
It makes sure there are no errors within the design, and makes sure any errors that are found within the design are rectified
136
What are some aspects that are checked within Design Validation?
Checks the design has met the objectives
Checks the design corresponds with the specification set during the analysis stage
Checks the most appropriate techniques have been used
Checks the user interface is appropriate for the audience
137
What is Design Evaluation?
When the development company and the client evaluate if the project has been successful
138
How does design evaluation effect the developers?
If the design evaluation is unsuccessful for them, then they might not get paid
139
What are the 5 key factors that are checked during design evaluation?
Requirements- has the project met the clear expectations set by the client?
Performance- is the performance optimal?
Robustness- is the server likely to crash/have bugs?
Cost- has the project ended in budget? (Little bit of tolerance offered)
Usability- how user friendly is the server?
140
What makes up the processor?
Registers, the CU and the ALU
141
What makes up the processor?
Registers, the CU and the ALU
142
What are the 2 tasks of components in a computer system?
Adding
Storing
143
What are the functions of the processors?
The fetch, decode, execute cycle
144
What is a register?
A temporary data store that holds the current instruction to be executed having been fetched from memory
145
What is the ALU?
The process and manipulation of data. Normally consists of arithmetic operations or logical comparisons that allows a program to make a decision
146
What is the CU?
Fetches each instruction in sequence, decodes it and then synchronises it before executing it. Sends control signals to other parts of the computer
147
What is the Von Neumann Bottleneck?
Limitation between the CPU and RAM is lower than the speed the CPU can process data
148
What is the Von Neumann Architecture?
When the data and the software are stored in RAM. The task being carried out by the computer can be changed by loading a different piece of memory
149
What has been developed against the Von Neumann Bottleneck?
Cache memory- temporary data store that is very close to CPU
Multithreading- allows multiple threads to be processed by the CPU simultaneously
Parallel processing- using multiple processors to handle different tasks at the same time
150
When is the Bottleneck created?
When the instructions are fetched at the same time as data operation on the same memory and bus system
151
What is the first step in the Fetch-Decode-Execute cycle?
The PC displays the next address in RAM of the next instruction to be processed
This value is copied into the MAR
152
What is the second step in the Fetch-Decode-Execute cycle?
The PC Register increases by 1
This prepares the CPU for the next instruction to be fetched
153
What is the third step in the Fetch-Decode-Execute cycle?
The CPU checks the address in RAM which matches the address held in the MAR
154
What is the fourth step in the Fetch-Decode-Execute cycle?
The instruction in RAM is transferred to the MDR
155
What is the fifth step in the Fetch-Decode-Execute cycle?
The instruction in the MDR is copied into the CIR
156
What is the sixth step in the Fetch-Decode-Execute cycle?
The instruction in the CIR is decoded and executed
Any result of the execution is stored in the ACC
157
What is Disk Fragmentation?
Files are split up and stored on different parts of the disc
158
What are some of the effects of Disk Fragmentation?
Increases disk head movement which disk access speed
159
What is Serial Computing?
Problem broken down into a series of instructions
Instructions are executed sequentially
Executed on a single core (one at a time)
160
What is parallel computing?
Problem broken down into a series of instructions that can be solved concurrently (at the same time)
Each part is broken down further into a series of instructions
Instruction are executed simultaneously on different processors
161
What are some limits of Parallel Processing?
Latency, Bandwidth
162
What is latency?
The amount of time it takes for data to travel from a device to the server, and back again
163
What is latency measured in?
Milliseconds (ms)
164
What is Bandwidth?
The capacity at which a network can transmit data
165
What is Clock Speed?
a measure of how many clock cycles a CPU can perform
166
What is Clock Speed measured in?
Gigahertz (GHz)
167
What is the Data Bus?
Any data from any component travels down the data bus
For example, data from RAM travels down the data bus to a register
168
What is the Address Bus?
Picks up the address (location) of data stored in RAM
Once an address is located, the data will travel down the data bus to the register
169
What is the Control Bus?
Sends and receives signals from all parts from all parts of the computer which makes sure all processes take place at the right time in the right order
170
What is an input device?
A device that gives instructions to the computer
171
What is an output device?
A device that carries out the instructions given to it
172
What is a hybrid device?
A device that is both input and output
173
Name some examples of input devices
Joystick, microphone, controller
174
Name some examples of output devices
Monitor, speaker, printer
175
Name some examples of hybrid devices
Mobile phone, laptop, iPad
176
What is Optical Character Recognition?
Converts an image or text into a format computers can understand
The computer saves the scan as an image file
177
What is Optical Mark Recognition?
Recognises marks made on certain paper documents in a certain colour
Used for school examples, etc.
178
What does OCR stand for?
Optical Character Recognition
179
What does OMR stand for?
Optical Mark Recognition
180
What is Magnetic Ink Character Recognition?
Prints characters on a document using a special ink that contains magnetic particles
Used in the banking industry
181
What does MICR stand for?
Magnetic Ink Character Recognition
182
What is Voiceprint Recognition?
Recognising the voicewaves in your voice so the software knows it's you
183
What is Voice Dictation?
When what you say gets typed up
184
What is ambiguity?
Words that sound the same but have different meanings
185
How is voiceprint recognition useful, in terms of data protection?
It will only understand a certain voice- the voice won't be able to be faked
186
How are most computers connected?
Through wired/wireless links
187
What is a computer network?
Interconnected computers that have the ability to communicate with one another
188
What does a network ned to work?
Switch/router and an ethernet cable
189
How do computers transmit data?
Through Wi-Fi
190
What is an NIC?
Allows data packets to travel between computers and network
Each NIC has its own unique 48 bit code called a MAC address
191
What is a MAC address?
a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment
192
What is a Router?
Forwards data when it arrives from one network to another
193
What steps happen when data arrives at a router?
Reads packet's destination address
Looks at all the paths to the address
Checks which path will be quickest
Sends packet down fastest path
194
What is a HUB?
Connects multiple computers together
Allows them to share data packets
195
How do computers communicate together?
Using a Protocol Suite (TCP/IP protocol)
196
How many layers is the Protocol Suite made up of?
4
197
What is the role of the layers within the Protocol Suite?
Each layer depicts what task is carried out by which protocol
Each layer has more than one protocol
198
What is the Application layer?
Allows the user to create messages that can be sent across the internet using a number of protocols
Any application will need the data to be formatted
199
What is the Transport layer?
Controls the flow of data across the internet
Breaks down messages into packets and labels them ready to be sent to other computers
Checks the packets have arrived safely
200
What is the Internet layer?
Delivers messages based on the address
Routes data between networks
Ensures relevant information is added to each packet (Destination Address, Source Address, Packet Number etc)
201
What is the Network Interface layer?
Physical connection that allows packets to be sent from one network interface to another
Determines how data is physically transmitted along a network
202
What protocols fall into the Application layer?
HTTP
FTP
POP
IMAP
SMTP
SNMP
203
What protocols fall into the Transport layer?
ICP
UDP
204
What protocols fall into the Internet layer?
IP
ICMP
205
What protocols fall into the Network Interface layer?
MAC
Ethernet
206
What is TCP (Transmission Control Protocol)?
Establishes connections between devices on a network, guarantees packets reach their destination
207
What is UPD (User Data Protocol)?
Sets up networks like a TCP, however doesn't guarantee the arrival of the packet
"Fire and forget"
Faster than a TCP
208
What is IP (Internet Protocol)?
Determines fields of information to be sent in packets (source address, destination address, packet number)
209
What is SMTP (Simple Mail Transfer Protocol)?
Mail server which stores sent mail until the user is online
210
What is POP3 (Post Office Protocol)?
Allows users to receive mail from the mail server
Used to download the email from the mail server
211
What is FTP (File Transfer Protocol)?
Controls how files are sent over the network
212
What is HTTP (Hyper Text transfer Protocol)?
Determines how the files that make up webpages are exchanged
213
What is SNMP (Simple Network Management Protocol)?
Allows certain administrative devices to see information about the devices connected to a network
214
What is ICMP (Internet Control Message Protocol)?
Handles transmission errors, alerts devices to any errors that have occurred and specifies what the issue was
215
What is a Network Standard?
A set of rules that enable hardware to be compatible with each other and communicate when sending and receiving data, using different hardware/software brands
216
What would happen without network standards?
Technology developed by different companies wouldn't work with each other, unless everyone used the same brand
We wouldn't be able to send/view different formats (sending a PDF to someone without a PDF reader)
217
What do protocols allow?
Protocols allow different devices to communicate with each other (computer to printer)
218
What is the Operating System?
Interacts with the users and applications, including the Kernel
219
What is the Kernel?
Manages system resources like the CPU, memory, I/O devices
Interacts with the hardware
Links the user, applications and hardware
220
What are the roles of the Operating System?
User interface- provides a general purpose interface to interact with applications
Security- deals with user access rights, typically through a password, device becomes a Multi-User OS
Backing store (secondary software)- The storage of the data on the hard disk
Utility software- Has other utility software involved, helps maintain software, increases life expectancy. File managers, firewalls, network managers, task managers ,etc.
221
What are the roles of the Kernel?
Peripheral management- oversees system devices which include I/O devices and storage devices. Ensures data exchanges between devices and applications, handling information flow
Memory management (RAM)- Kernel allocates and deallocates memory for processes by keeping track of the sections of memory. Stores active processes in memory, releases memory when processing ends
Process management (CPU)- Kernel allocates time to each process. After a process completes its execution, the Kernel starts the next one and assesses it's state (ready, running, blocked)
Interrupt handling (CPU instructions)- Kernel manages task priorities, allowing high-priority tasks to take precedence. Handles system calls (essentially software interrupts)
222
What is the Ready State?
A state in which a process is ready and waiting for its execution
223
What is the Blocked State?
A state in which a process doesn't execute unless a process event occurs (completion of an input/output operation)
224
What is the Running State?
A state in which a process is currently executing
225
What is Time Slicing?
Allowing each process a short interval of processing time on the CPU
226
What is Paging?
Enables processes to access more memory than is physically available
227
What is Segmentation?
Organises and allocates memory for processes in flexible and module manner
228
What are Interruptions?
Stops a program running. Can be a computer stopping a program (closing a window) or a virus
229
What is a High Level Interrupt?
When interrupting a program can damage the software
230
What is a Low Level Interrupt?
When interrupting a program has no effect on the software
231
What is Data Transmission?
The way in which data can be transferred between devices within a computer network and between devices connected to it
232
What are the two ways data can be sent?
Parallel, Serial
233
What is Serial Transmission?
Data is split up into packets and sent one by one across a single wire
234
What are some features of Serial Transmission?
Used over long distances (e.g. computer and printer), slower than parallel
235
What is Parallel Transmission?
Data is sent over multiple wires, bit by bit, that are parallel to each other
236
What are some features of Parallel Transmission?
Data is sent over small distances (e.g. within a computer system), faster than parallel, has the skew effect
Suitable for scenarios which need a high transfer rate
Needs more advanced hardware and cabling
237
What is the skew effect?
Time distance between multiple pieces of data being transferred. Millisecond difference, not noticed by humans
238
What are some advantages of serial transmission?
Low power consumption
Low cost
Simple hardware and cabling
Suitable for long-distance communication
239
What are some disadvantages of serial transmission?
Not suitable for large amounts of data
Slow data transfer rate
Limited bandwidth
240
What are some advantages of parallel transmission?
High transfer rate
Suitable for large amounts of data
241
What are some disadvantages of parallel transmission?
Higher power consumption
Higher cost
Limited maximum cable length
Complex hardware and cabling
242
What is multiplexing?
Managing various signals between devices
243
What are the three common methods of multiplexing?
Simplex, half-duplex, full-duplex
244
What is simplex?
Data can be sent in one direction and one direction only, e.g. a speaker
245
What is half-duplex?
Data can be sent in both directions but only one at a time, e.g. a walkie talkie
246
What is full-duplex?
Data can be sent in both directions at the same time, e.g. a mobile phone
247
What is switching?
The process of transferring data from one device to another
248
What are 2 common methods of switching?
Packet switching, circuit switching
249
What is packet switching?
Breaking down data into packets, sending them across a network and then reassembling them at their destination address
250
What is circuit switching?
A dedicated communication path between two devices for communication
251
What are the 3 parts to a TCP packet?
Trailer, payload, header
252
What is the purpose of the Trailer?
Informs recipient's device that the packet has been received
253
What is in the Payload?
The data being transferred
254
What is in the Header?
Source Address (allows tracing of sender)
Checksum (calculation that checks for errors)
Packet number (allows packet to be reassembled correctly at end)
Packet address (allows packet to be routed to destinsation)
255
What is a network collision?
Two devices on the same network attempting to send data at the same time
256
What happens to packets after they collide?
They get discarded
257
What are Boolean Laws?
Boolean identities (laws) are the rules that are used to simplify Boolean expressions
258
What does each Boolean Law have?
Each Boolean law has an AND form and an OR form, depending on what is being used
259
What is the Commutative Law?
Law that switches order of expression
A.B = B.A
A+B=B+A
260
What is the Idempotent Law?
Law that removes repetition
A+A=A
A.A+A
261
What is the complement Law?
Law that inverts something equal to the term (cancelled if there are two NOT's over a term)
A.¬A=0
A+¬A=1
262
What is the Identity Law?
Law that simplifies statements down to A, whether a statement is AND'd with a 1 or OR'd with a 0
A.1=A
A+0=A
263
What is the Annulment Law?
Law that simplifies statements down to a 0, whether it is AND'd with a 0 or OR'd with a 1
A.0=0
A+1=1
264
What is the Absorption Law?
Law that reduces a bracket to 1 value
A.(A+B)=A
A+(A.B)=A
265
What is the Association Law?
Law that separates brackets that use the same operator inside and outside the bracket
A.(B.C)=A.B.C
A+(B+C)=A+B+C
266
What is the Distribution Law?
A law that uses the value outside the bracket and multiplies with bow values inside the brackets, forming two new brackets which are linked by the operator formally inside the bracket
A+(B.C)=(A+B).(A+C)
A.(B+C)=(A.B)+(A.C)
267
What is De Morgan's Law?
"Split the line, change the sign"
¬(A.B)=¬A+¬B
¬(A+B)=¬A.¬B
268
What is data stored in?
Files
269
What happens when a file is stored on a hard-disk?
It is given a name and the OS keeps a record of the address on disk using a File Allocation Table in order to locate the stored file
270
Why is data within files organised?
Organised so the OS can find these files easier and not abuse the hard disk
271
What happens every time we create, modify, move or delete a file?
The file info is recorded by the OS into a File Allocation Table (FAT)
272
What is a FAT?
A method of keeping track of the contents of a hard drive, used by Microsoft in early OS'. Still used today in most embedded systems
273
What is on the FAT?
Chart of numbers that corresponds to cluster addresses on the hard drive. if a file is large/dispersed across different tracks on a hard disc, these are also recorded
274
How is data stored on a hard disc?
Stored in 'sectors', and these sectors are stored in 'clusters'
275
What does each cluster get?
Each cluster gets a number. This number is also stored when data ges saved
276
What are some advantages of clusters?
Minimises fragmentation, allocates clusters that are contagious allowing for efficient use of disk space
277
What are some disadvantages of clusters?
Constant altering of files leads to empty clusters, leading to fragmentation
278
What is a field?
Single data item that can be grouped together or split
279
What is a record?
Collection of related fields (information about someone)
280
What is a Fixed Length Record?
Records with the same number of bytes and same number of fields
281
What are some advantages of Fixed Length Records?
Easier to program
Easy to manage
282
What are some disadvantages of Fixed Length Records?
May require padding (any blanks are padded out with an empty space)
283
What is a Variable Length Record?
Records with a different number of bytes and a different number of fields
284
What is an advantage of Variable Length Records?
No padding required
285
What is a disadvantage of Variable Length Records?
No padding required
286
What are the two types of file?
Transaction files
Master files
287
What are master files?
Principle file that stores crucial information about a business, held by an organisation
288
What are transaction files?
Contains the day-to-day information generated from business activity. Used to update/process the master file
289
What are some File Access Methods?
Serial File
Sequential File
Indexed Sequential File
Multilevel Indexed Sequential File
Direct Access (Random) File
290
What are Serial Files?
Files that store data in the chronological order they have arisen. Needed when data is needed in chronological order
291
What are some features of Serial Files?
When a specific file is needed- will need to search 1-by-1 through every file
Used as temporary transaction files, never used as a master file
292
How are records searched for in a Serial File?
Every record is copied in the order it is stored in to a new file. The one you are looking for is NOT copied. The old file is deleted, the new file is updated
293
What are Sequential Files?
Records are stored in some sort of order using a Primary Key (field with a unique value to that field)
Order is based on a field in the record
294
What are some features of Sequential Files?
Simple
Efficient
Overall process is slow
295
What are Indexed Sequential Files?
Same as Sequential File, but you can use an index to search for files (like the encyclopaedia of a book)
296
What are search engines?
Software system designs that carry out web searches. Searches the web for information based on the keywords/phrases entered by the user.
297
What are the 3 sections of internet searching?
Crawling
Indexing
Ranking
298
What is crawling?
Specialist feature that is always checking for new software
299
What is indexing?
Ordering software in terms of importance/usefulness. Also checks if webpages stored in database are active so it can be removed if needed.
300
What is a database, in terms of web searching?
Store of webpages are there are so many that exist.
301
What is ranking?
Ranking results based off their relevance to the search
The adding of a website's content to be considered for ranking
302
What is the process of crawling?
Start with fetching a few webpages
They follow the links off those webpages to find new content
The new content is added to and stored in the indexer
Crawlers revisit pages periodically to check for updates
303
How can content vary?
Can vary on find- webpages, pdf documents, images, videos etc.
304
What is robots.txt?
A standard used by websites to indicate to crawlers which parts of the site they can access
305
Why can't crawlers check all of a website sometimes?
Some parts of the website get denied as they are private- they wouldn't want the public seeing it. It may also be irrelevant
306
What happens as soon as a new/updated webpage is found?
As soon as a new/updated webpage is found, it has to be indexed
307
What is the index?
A massive online library helping the search engine find relevant results
308
What is the process of indexing?
1. Search engines send out pieces of code to ferret out new or updated content on the web
2. As the search engines crawl through a new site, they make note of any outgoing links they'll need to crawl as well
3. The search engine indexes all the new content they have found and input that data into a huge database
309
What is metadata?
Helps search engines efficiently index data in order. Only works if data is already in order. Can filter out data that doesn't fit the search
310
What is ranking?
The order that results are displayed in after a search. Different algorithms are used to determine the rankings. The algorithms change regularly so webpages need updating to maintain a high rank
311
How does a website increase rank?
Use more keywords
Relevance of content
Sponsorship
Security of website
Engagement metrix
Backlinks (research)
User experience
On-page SEO (research)
Domain authority (research)
Time user spends on website
312
What is an operating system?
Software that allows a computer to run as well as manage the software, user interface and all other software running on the computer.
313
What would happen without an OS?
Without an OS, a computer wouldn't work- it would just be a collection of parts
314
What are the 3 types of OS?
Single user, single application
Single user, multi-tasking/multi-programming
Multi user, multi-tasking/multi-programming
315
What are the 2 types of single user system?
Single user, single application
Single user, multi-tasking-multi-programming
316
What is single user, single application?
OS can only deal with one person at a time, running one user application at the same time (e.g a mobile phone)
317
What is single user, multi-tasking?
Designed to deal with a single user, but can deal with many applications running at once 9doing homework, searching the web and downloading a music file is an example- a PC is too)
318
What is a multi-user OS system?
Allows many different users to use a computer's resources simultaneously. The OS needs to balance the requirements of the users, and each program has sufficient resources
319
What is multi-programming?
Keeping several programs in memory at once- only one program will run. When the current running program temporarily stops, the OS will switch the CPU to run another program in memory. The processor is so fast to give the appearance many jobs are being processed at once
320
What is multi-tasking?
The OS makes the CPU switch between all the programs very quickly (time slicing). Runs one program for a bit, switches, runs a different one for a bit, switches, and repeats that process. Switches very fast (in miliseconds). Creates the illusion all the programs are running at once
321
How does the CPU multitask?
Time slicing
Polling
322
What is time slicing?
Allocating each program a small section of time for the CPU to run that program
323
What is polling?
The computer waiting for an external device to check its readiness or state, often with low-level software
324
What are the 4 modes of operation?
Real time control
Real time processing
Interactive
Batch processing
325
What is batch processing?
Collecting data over a set period of time before processing the data in one job lot. No human intervention required during processing (e.g phone bill)
326
What is real time control?
Dealing with the input immediately in order to act upon the input and produce an output (traffic lights)
327
What is interactive?
Processing that acts on the input given by the user (getting hotel websites after searching for holidays)
328
What is real time transaction?
Happens after interactive processing has occurred. (After you enter your card details to book a holiday, money is taken from your account and the system updates availability immediately)
329
What are the advantages of Batch?
Efficient in terms of resource usage
No direct communication between users
Easy to use
330
What are the advantages of real time control?
Efficient algorithm scheduling
Limited tasks
Maximises performance
331
What are the advantages of Interactive?
Real time interaction
332
What are the advantages of real time transaction?
Improved cash flow
333
What are the disadvantages of batch?
Debugging takes time
Computer operator must be changed
High turnaround time
334
What are the disadvantages of real time control?
Frequent driver crashing
Driver request
Poor multitasking
335
What are the disadvantages of interactive?
Small chance of creating an infinite loop
336
What are the disadvantages of real time transaction?
Expensive
Complex
Tedious
337
What are interrupts?
Signals generated by software/hardware to indicate to the processor that a process needs attention
338
What is the process of interrupting?
1. Interrupt signal sent to processor through OS
2. Processor receives this signal and suspends what it is currently doing
3. It saves its state and launches an interrupt handler which then deals with the interrupt
339
What is an interrupt handler?
Feature that identifies what signal has come through (is it hardware or software, high level or low level, etc)
340
What is a hardware interrupt?
Deals with hardware interrupts (keyboard and mouse)
341
What are software interrupts?
Deals with programmed exceptions to help deal with events that can't be dealt with within a program (dividing by 0)
342
What is the ISR (Interrupt Service Routine)?
1. Processor checks if there is content in interrupt processor
2. If there is nothing in the register, the FE cycle continues like normal
3. If there is a signal, the processor's contents are temporarily stored in a stack
4. Processor loads the ISR into RAM
5. A flag is sent to the ISR. Once the interrupt has been serviced, the flag is reset
6. Interrupt queue is checked for any more higher priority interrupts to the originally executed process
7. Contents of the stack are transferred back into registers in memory. The FE cycle resumes
343
What is the order of priority in the ISR?
1. Hardware failure
2. Program
3. Timer
4. I/O
344
What does each running program have allocated to it, and what must this memory not do?
Memory, interfere with memory allocated to other programmes
345
What part of the computer is responsible for memory management?
The OS
346
How much memory should be allocated to a task?
An appropriate amount of RAM
347
What should happen to the RAM after a task has been completed?
The RAM should be 'returned' to then system so it can be used for other tasks
348
How does the OS carry out memory management?
Partioning
349
Why is memory management important?
Allocates and deallocates memory before and after process execution
Keeps track of used memory space by processes
Minimizes fragmentation issues
Properly utilises main memory
Maintains data integrity while executing processes
Prevents memory waste
Ensures a fair allocation of resources
Prevents interference within each process
350
What is partitioning?
Separating a section of hard drive from other sections
351
Why is partitioning good?
Makes organisation of data easier
Easier to backup partitions separately
Improves hard disk performance (works better with small chunks of data)
352
What is the role of virtual memory?
Efficiently manages memory allocation and maximises the utilization of RAM
353
Other than separating the hard disk, how else can partitioning be used?
Sectioning off memory to utilize memory locations effectively
354
What doe the OS keep track of, in terms of memory?
Keeps track of the address of where the memory is stored
355
What does buffering manage?
Manages file space
356
What does buffering temporarily store?
Temporarily stores data while other data is being moved from one place to another
357
What is buffering?
Small area of memory set up as a temporary store of data until it is ready to be used
358
How does buffering speed the computer up?
Tries to get slower devices to work with faster devices to prevent delays
359
Give an example of where a buffer might be used
Streaming- the computer system might be faster than the film, so buffering occurs
360
Why do we need buffers?
1. Speed issues: devices often work at different speeds (the CPU processes data faster than a hard drive can read/write data)
2. Smooth data flow: instead of sending data bit by bit as it becomes available, a buffer collects enough data to be sent in one go, which is more efficient
3. Handling interrupts: buffers reduce the number of times the CPU has to pause its current execution to deal with the interrupts, which makes the system more efficient
361
What are some downsides of buffers?
Data can't be added and removed from a buffer at once
If a buffer is full, it can't be emptied
362
What process is used in order to get around the issues of buffering?
Double buffering
363
What are the 4 steps of double buffering?
1 Buffer 1 fills up with data
2. Once buffer 1 is full, data begins to fill up buffer 2
3. While buffer 2 is being filled, buffer 1 is being emptied
4. After step 3, the process reverses- buffer 2 is emptied and buffer 1 is filled, and so on
5. These 4 steps repeat until all data has been used
364
When is double buffering used?
Used when data can't be "turned off", e.g while you are streaming a film
365
How does double buffering aid the computer?
They prefer to handle "chunks" of data which double buffering produces
366
When is scheduling needed?
In a multi-user environment, when several users will need servicing, seemingly at the same time
367
What is scheduling?
An OS that schedules processes of a different state, allowing the OS to time slice. Keeps the CPU busy at all times
368
What does a scheduler manage?
Which process will be executed next
The length of time it can be executed for
When the current execution becomes blocked/suspended or finishes, the next instruction in line will execute
369
What can happen to the new instruction in line?
Finish processing
Get blocked (requires an I/O command) meaning it can't continue until more data is needed
Run out of allocated processing time, get suspended and move to the back of the queue
370
What is FCFS (first come, first serve)?
Each process is executed in the order they come in. If a process takes a while, the other processes have to wait. Doesn't consider priority and is time consuming
371
What is SJF (shortest job first)?
OS picks out process that will take up the least amount of processing time and executes it. Scheduler finds out how long each program will take and orders them from fastest to slowest. No equal share of time slice
372
What is RR (round robin)?
Each process gets an equal amount of processing time (time slicing). If a process isn't fully executed, it goes back in the end of a queue and executes again
373
What is STR (shortest time remaining)?
Like SJF, but it factors in priority
374
What is the purpose of a scheduler?
processes as many tasks as possible in a given time
Makes maximum use of CPU time
Minimises user delay between the input and the output
Makes maximum use of resources, i.e I/O devices
Priorities jobs
Ensures no job is left uncompleted for too long even if they are low priority
Alters priority according to needs
375
What are some common interfaces?
GUI (graphics user interface)
Form/menu
Natural language
Command line
376
What is natural language?
Interacting using normal, everyday language. Understands the meaning of conversation and reacts accordingly. Mostly used by people who struggle using technology
377
What are some advantages of natural languages
Easy to learn
No experience needed to use
Speeds up text input
Allows the user to simultaneously complete other tasks
Reduces RSI (repetitive strain injury)
378
What are distributed databases?
A type of database that is spread across multiple locations or computers, often connected over a network
379
How is data distributed across distributed databases?
Data is distributed across several servers or nodes, which can be located across multiple different physical locations
These nodes work together to store, manage and process all the data, making the system more reliable, scalable and faster for handling large amounts of data
380
How do users access distributed databases?
Users/applications access the database as if it was one large database, despite being multiple databases located across multiple different locations
381
What is a good example of a distributed database?
The NHS- it appears to be one large body, however it as many subdivisions (hospitals, GP's NHS dental, ambulances, pharmacies, private medical services)
382
Can all nodes on a distributed database access all the data?
No- using the NHS example, pharmacies can't access your entire medical history, only what is required for your prescription
383
What is big data?
Large, complex sets of data that are too large or complicated for traditional data-processing applications, such as databases
384
How do organisations face difficulties with big data?
Capturing, storing, analysing, sharing, transferring, querying/manipulating data
385
What is big data referred to?
The use of "predictive analytics"
386
What is predictive analytics?
A method of extracting values from data from a particular data set (we know this as data manipulation!)
387
What are some features of distributed databases?
Data distribution (data is distributed across multiple sites)
Replication (data can be replicated across multiple sites for redundancy and high availability)
Transparency (users interact with the database as if it is one big database despite it being multiple smaller databases)
Autonomy (each site can function independently, though they co-operate
Scalability (can handle large amounts of data by adding more servers)
388
What is secondary storage?
Any storage that is additional to and removeable from the msin computer storage
389
What are some functional characteristics of secondary storage?
Speed of access
Cost per unit
Portability
Durability
390
What are some features of big data?
Volume: extremely large amounts of data
Velocity: high speed of data generation (real time data)
Variety: different types of data (structured, semi-structured, unstructured)
Veracity: uncertainty about data (quality and trustworthness)
Value: the usefulness of data
391
What are the advantages of distributed data?
Scalability: new nodes can be added easily
Cost effective: no need to set up new databases
High availability: there will always be 1 part of the database that remains operational
Sharing of resources (databases)
392
What are the disadvantages of distributed data?
Complexity: it is complex to manage and maintain distributed data
Latency: might be delay between sides when communicating
Consistency issues: handling data consistency can be challenging
Security: more complex security measures are required
393
What are the advantages of big data?
Improved decision making: big data analytics help organisations make informed decisions
Innovation: unlocks new opportunities for products, services and business models
Efficiency: optimises processes in industries like healthcare, manufacturing and logistics
394
What are the disadvantages of big data?
Data privacy: handling personal data ca be tricky
Storage costs: storing large amounts of data requires lots of infrastructure
Complexity of analytics: extracting valuable insights from big data requires specialised skills and tools
Data quality: ensuring data is accurate and clean is difficult with such large data sets
395
What is data comression?
Encoding information using fewer bits than the original representation
396
What are the 2 types of data compression?
Lossy, lossless
397
What is lossy compression?
Some data is removed and discarded, reducing the overall size of the file
398
How can images be compressed?
Reducing the colour depth (which reduces the range of colours in an image, resulting in an average range of colours)
399
How can audio files be compressed?
Reducing the number of samples
400
Name an example of a lossy audio file format
MP3
401
What is truncating?
Reduction in quality
402
What is the number of possible integer values (per sample) per 4 bits?
16
403
What is the number of possible integer values (per sample) per 8 bits?
256
404
What is the number of possible integer values (per sample) per 11 bits?
2046
405
What is the number of possible integer values (per sample) per 16 bits?
65,536
406
What is the number of possible integer values (per sample) per 20 bits?
1,048,576
407
What is the number of possible integer values (per sample) per 24 bits?
16,777,216
408
What is the number of possible integer values (per sample) per 32 bits?
4,294,967,296
409
What is the number of possible integer values (per sample) per 48 bits?
281,474926,710,656
410
What is the number of possible integer values (per sample) per 64 bits?
16,446,744,073,709,551,616
411
What is lossless compression?
Files are reduced in size without the loss of data
412
What are some examples of lossless compressions?
Text files, spreadsheets, financial records, e-mails, etc
413
Name 2 techniques of lossless compression
RLE
Huffmann coding
414
What is data security?
Protecting data from external/internal threats
415
What security issues do organisations face with data?
Outside access and manipulation of data
Unauthorised reading/copying of files
Corruption of files
Loss or deliberate deletion of files
416
What is data integrity?
Ensuring all data is as accurate as possible and does not contain accidental errors or multiple different versions of data are stored
417
What are some impacts of data loss?
Financial loss
Reputation stained
Increased costs
Legal impacts
Operational impacts
Changes to organisation practise
Theft of intellectual property
Loss of customers
418
How do you improve data protection?
Implement strict policy
Passwords must be hard to guess
Limit access level rights (read access vs read and write access)
Firewalls
Read and lock
Encryption
419
What is a firewall?
Piece of software that checks all connections to the software and makes sure unethical hacking occurs
420
What is read and lock?
Locking files when the file has been downloaded for updating, not allowing file access until the updated file has been reuploaded
421
What do safeguards protect files from?
Hardware failure
Software failures
Human errors
Deliberate errors
422
What are some methods of file security?
Physical security
File backup
Transaction log
Archiving files
Passwords
Encryption
423
What is physical security?
Physical instalments to protect data
424
What is file backup?
Making copies of files incase you lose the main files so you have a backup
425
What is a transaction log?
Keeping track of everything that happens
426
What is data validation?
Check done by the computer as to whether data is/isn't acceptable to be processed
427
What are the types of validation checks?
Presence check
Range check
Type check
Format check
Look-up check
Length check
Check digit
428
What is presence check?
Makes sure data is present in certain fields
429
What is type check?
Makes sure data is the correct type
430
What is format check?
Makes sure data follows a particular picture or pattern
431
What is look-up check?
Makes sure data is one of the values listed ina drop down box
432
What is length check?
Makes sure data has the correct number of characters
433
What is check digit?
Calculation on numerical data only
434
What are predictive analytics?
Predicting things that may be useful to some (the " suggested for you" tab on shopping sites)
435
What is data mining?
Sifting through data in order to find interesting patterns (large supermarkets track people's shops via the loyalty card to look for patterns)
436
What is data warehousing?
Central storage place where data from different systems are brought together are organised (like a library where all the different genres are organised)
437
What are some advantages of serial files?
Simple file design
Very efficient when all files need processing
Efficient when no order is required
438
What are some disadvantages of serial files?
Searching for a particular algorithm is inefficient (every algorithm needs checking until it is found)
Difficult to sort records in order
439
What are some advantages of sequential files?
Simple file design
Efficient when most records need processing (payroll)
Very efficient of data has natural order
440
What are some disadvantages of sequential file?
Overall process is slow
Transactions need sorting before processing
Entire file must be processed even if you are only searching for 1 record
441
What are some advantages of random access file?
Any record can be directly accessed
Speed of processing records is fast
Up-to-date, online updating
Concurrent processing is possible
442
What are some disadvantages of random access files?
More complex than sequential
Never fully uses memory locations
More security problems
