march ppe Flashcards
finished
1
Q
Define debug
A
The process by which a programmer finds and corrects errors in code.
2
Q
What is syntax?
A
The rules that govern how the pieces of a programming language can be put together to make meaningful instructions, similar to grammar and punctuation in English.
3
Q
What is the IDE?
A
A package that helps programmers to develop program code.
4
Q
Define a ‘reserved word’
A
Any keyword in the programming language that programmers are unallowed to change.
5
Q
What is a literal?
A
Values in code such as numbers of characteristics inside quotes. They can’t be changed during execution.
6
Q
What is a high level language?
A
A programming language that resembles human language and enables a programmer to write code that is independent of a particular CPU’s architecture.
7
Q
What is a low level language?
A
A programming language that is closer to machine code than human language and requires detailed knowledge of a particular CPU’s architecture.
8
Q
What is a type error?
A
When an operation is attempted that is invalid for that type of data.
9
Q
What is a runtime error?
A
An error that occurs when the program is running.
10
Q
What is a name error?
A
When a name is used that isn’t known about (often a misspelt variable name)
11
Q
What is a zero division error?
A
Dividing a number by zero.
12
Q
Define a ‘KeyboardInterrupt’
A
When a program is interrupted from the keyboard by pressing control + c.
13
Q
Who created Boolean?
A
George Boole.
14
Q
What is a breakpoint?
A
A mechanism to mark a line of code, where execution is paused.
15
Q
Define the single step process.
A
Executing one line of code at a time using a debugger.
16
Q
What is a syntax error?
A
When part of the code breaks the rules of the programming language.
17
Q
What is a runtime error?
A
An error that occurs while the program is running. The operation the computer is asked to do is impossible to execute. Often causes crashes.
18
Q
What is a logic error?
A
An error in an algorithm that results in incorrect, unwanted or unexpected behaviour.
19
Q
What are the rules of a variable?
A
A variable must not:
- begin with a number
- include a space
- be named the same as a reserved term
20
Q
Give the 6 relational operators and their names.
A
- Equal to ==
- Not equal to !=
- Greater than >
- Greater than or equal to >=
- Less than <
- Less than or equal to <=
21
Q
What are the 4 programming constructs and their associated loops.
A
Selection -> IF statement
Repetition -> WHILE loop
Iteration -> FOR loop
Sequence: Linear code, ordered
22
Q
What is the range function?
A
Function used to count. If there’s 1 number in the bracket, the counter will start at 0 and count up in 1s until it hits the parameter (number in bracket).
If there are 2 numbers, they are the start and end numbers.
Elif there are 3 numbers, they are the start, end and step (how many the program will count by) numbers.
23
Q
What is version control?
A
A way to keep track of changes to code so that programmers can go back and retrieve previous working programs.
24
Q
Define ‘backup’
A
The process of creating backup copies of data and storing them in a separate location, usually the cloud.
25
What is an algorithm?
The precise step by step method to solve a specific problem.
26
Define decomposition.
The breaking down of ideas into smaller parts.
27
Define abstraction.
The process of removing or hiding unnecessary details so only the most important points remain.
28
What is generalisation?
Taking an algorithm for specifics and modifying it to solve similar or new problems.
29
What is an evaluation?
The making of judgements about requirements about efficiency and whether there are other solutions.
30
Define transistor.
Tiny electronic component with just 2 discrete states - high voltage (on) and low voltage (off). Billions of these are combined in complex integrated circuits and etched on the surface of silicon chips used in computer systems.
31
What is binary?
Data represented by just 2 values (high/low, on/off, 1/0)
32
Bits vs. Nibbles vs. Bytes
A bit is the smallest unit of data in a computer. A nibble is 4 adjacent bits that can produce 16 different bit patterns. A byte is 8 adjacent bits or 2 nibbles that can produce 256 different binary patterns.
33
Define ASCII.
7-bit binary code used to represent text. with each character assigned a value between 0 and 127.
34
What is the MSB?
The most significant bit. It's the left most bit of a binary number with the highest place value. In a byte, the MSB has a weight of 27.
35
What is the LSB?
The least significant bit. The right most bit of a binary number with a place value of 20.
36
Define overflow error.
The error that occurs when a calculator produces a result greater than the computer can store.
37
What is two's complement?
Used to represent signed numbers. The MSB of the 2's complement number indicates whether it's positive or negative. If the MSB is 0 it's positive. If the MSB is 1 it's negative.
The range of values that can be presented by 2's complement bytes is -128 to +127.
38
What is a binary shift?
Used to move all bits in a binary pattern left or right.
39
Define logical shift.
Treats all bits of a binary pattern the same, irrespective of what the pattern represents.
40
What is an arithmetic shift.
A binary shift left or right. When performing a right shift, the cleared positions on the left are filled with copies of the MSB. When performing a left shift, the cleared position on the right are replaced with only 0s.
41
What is hexadecimal?
A base-16 number system designed to make handling long patterns of binary digits easier for humans.
0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F -> 16 digits
42
What are the rules for binary addition?
0+0 = 0
0+1 = 1
1+1 = 0 carry 1
1+1+1 = 1 carry 1
43
How to convert binary to denary?
Make a grid 128 - 1 and input the binary number. Then simply add it up.
e.g:
128|64|32|16|8|4|2|1
0 | 0 | 1 | 0 |1|1|0|1 = 32+8+4+1 = 45
44
How do you convert hexadecimal to denary?
Make a 256,16,1 grid. Then multiply the numbers by their place values and add them together.
e.g hex 14F
256|16|1
1 | 4 | F
means (1*256)+(4*16)+(15*1) = 256+64+15 = 335 in denary
45
How do you convert hexadecimal to binary?
Convert each digit to denary, then each denary number into 4-bit binary numbers.
e.g hex AC
A -> 10 -> 1010
C -> 12 -> 1100
AC = 10101100
46
How do you convert binary to hexadecimal?
Break the byte into nibbles, then using a 8-1 grid, convert into a denary number. Then denary -> hex.
e.g 11100110
1110 and 0110
8|4|2|1 8|4|2|1
1|1|1|0 0|1|1|0
= 14 = 6
11100110 = E6
47
How to convert denary to hexadecimal?
Divide the number by 16 and record the remainders. **The answer is the remainder starting at the last value**
e.g 47
47 / 16 = 2 r 15
2 / 16 = 0 r 2
15 = F, 2 = 2
47 = 2F
48
Define pixel.
A single dot of colour and is the smallest element of a bitmap image.
49
What is image size resolution?
The size of an image, represented as width*height in pixels.
50
What is colour depth?
The amount of colours that can be represented. As it increases, so does the amount of colours that can be repped. Using 8 bits, 256 colours can be represented (28)
51
What is the current standard for colour depth?
24 bits. 8 bits each for red, green and blue. Over 16 million colours can be represented (known as true colour).
52
What is the equation for the file size of a bitmap image?
Width \* height \* colour depth (bits) = file size
53
What is the scale of bytes?
From smallest to biggest: Bit, nibble, byte, kibibyte, mebibyte, gibibyte, tebibyte.
54
How do you convert from bits to bytes?
Divide by 8.
55
How do you convert from bytes to kibibytes, kibibytes to mebibytes and so on?
Divide by 1024.
56
Define amplitude.
The measurement of the distance the wave is from the axis at a point in time.
57
Define analogue.
Using signals or data represented by a quantity that is continuously changing.
58
What is sampling?
Taking measurements of the amplitude of a sound wave at regular intervals of time.
59
What are sampling points?
Discrete points in time at which a reading of the amplitude of the sound is taken and stored as a binary number.
60
Define a sampling interval.
The time between samples measured in seconds. It produces a better sound than the original sound but increases file size.
61
What is the sample rate/frequency?
The number of sound samples taken per second, measured in hertz (Hz). The higher the sampling rate, the more accurately the sound will be reproduced in the file.
62
What is bit depth?
The number of bits needed to represent the range of values in the y-axis.
63
In a graph of a sound wave, what do the x-axis, y-axis and line represent?
Y-axis = binary values
X-axis = time values
Line = the sound wave
64
How do you calculate the file size of a sound file?
Sample rate (s)*Bit depth (bits)*Duration of recording (s) = file size (bits)
If sample rate is expressed in kHz, keep in mind 1 kHz = 1000 cycles per s.
65
Define input.
The data sent to a computer for processing.
66
Define output.
Data that was processed by and sent out from a computer.
67
What is hardware?
The physical components of a computer system.
68
What is software?
The set of programs running on a computer which direct it to perform its specific operations.
69
What is a program?
An algorithm that has been converted into program code so that it can be executed by a computer.
70
Explain the stored program concept.
Both the program instructions to be executed and the data to be used are stored together in the computer's main memory for as long as needed.
71
Define main memory?
Temporary store for data and program instructions.
72
What is computer architecture?
The design of a computer - what hardware components it has and how they are connected.
73
Define CPU.
The central processing unit. The hardware component that carries out the processing in a computer.
74
What is secondary storage?
Non-volatile, long term storage for programs and data.
75
Define RAM.
Random Access Memory, a computer's main memory. Locations in ram can be accessed in any order directly. It is volatile (lost when power is turned off)
76
What is a memory address?
The binary number that uniquely identifies a location in memory.
77
Define 'writing to memory'
Transferring an item of data from the CPU into memory.
78
Define 'reading from memory'
Transferring an item of data out of memory into the CPU.
79
What is the control unit?
The part of the CPU that decodes instructions received from main memory and coordinates the actions of other parts of the CPU to execute them.
80
What is the ALU?
The arithmetic logic unit. It's the part of the CPU that performs arithmetic and logic operations on data.
81
What are registers?
Storage locations inside a CPU to hold data.
82
What is an accumulator?
A special purpose register within the CPU that stores results of operators carried out by the ALU.
83
Define instruction register.
Stores the instruction currently being executed held within the CPU.
84
What is the address bus?
Carries the address of the memory location that the CPU will read from or write to. It's unidirectional.
85
What is the data bus?
Holds the value being read from or written to memory. Bidirectional.
86
What is the control bus?
Carries control signals between the control unit and other components, bidirectional.
87
Define bus width.
The number of wires that make up a bus. It determines the range of binary patterns that can be transmitted.
88
What is a clock?
An electronic device that ticks at regular intervals, used to synchronise the actions of the CPU.
89
Define pipelining.
A way of improving the CPU. The stages of the fetch-decode-execute cycle are overlapped: while the CPU is executing one instruction, it's decoding another and fetching another.
90
Why was the stored program concept a breakthrough concept?
Because it meant you can easily go from one task to another in the same device by simply switching the memory.
91
Explain the fetch-decode-execute cycle.
- FETCH: The control unit (CU) places the memory address of the next instruction onto the address bus. Then the CU sends a signal through the control bus to the RAM. When the signal is received, the RAM copies the memory location from the address bus onto the control bus.
- DECODE: The control unit decodes the instruction
- EXECUTE: The CU sends instructions and signals to other parts of the CPU, telling them what to do.
92
What is data capacity?
The amount of data that can be stored in a computer's memory or on a storage device such as a hard drive. It is measured in Kib, Mib, GiB and TiB.
| to convert from Mib -> Kib -> Bits,** multiply by 1024**
93
What does von Neumann architecture consist of?
Main memory (RAM) and a CPU, interconnected by buses.
94
What are most modern computers made up of?
- A CPU that contains an ALU and processor registers
- A CU that contains an instruction register and program counter register
- Memory that stores both data and instructions
- External data storage
- Input and output mechanisms
95
What is a ROM?
Read Only Memory. It permanently only stores the boot up program (BIOS).
96
What is a HDD?
Permanently stored secondary storage.
97
Define logic gate and the 3 main types.
The basic component of digital circuits, taking 1 or 2 inputs and producing a single output based on a rule.
There are: NOT, AND and OR.
98
What is a truth table?
A table showing all possible combinations of inputs and outputs of an operator.
99
What is magnetic storage?
A physical way of recording physical binary data by utilising the fact that magnets have north and south poles, which can be used to represent 1s and 0s.
100
How do you write, store and read data using magnetic storage?
- WRITING: the heads alter the magnetic state of the surface of the disk
- STORING: there is magnetic coating on the surface of the media. the magnetic state can be charged to represent a 0 or a 1.
- READING: the magnetic state is detected from each area on the disk. An area that is demagnetised is 0. Magnetised areas are 1.
101
Give 2 examples of magnetic storage.
- Hard drives
- Magnetic tape drives
102
What is optical storage?
A physical way of recording binary data by using differences in light reflected off the surface of a disk to represent bits.
103
How do you write, store and read data using optical storage?
- WRITING: the laser heats the recording material, which changes its form to become more or less reflective. Reflective areas are lands (1) and less reflective areas are pits (0).
- STORING: as a series of pits (bumped areas - 1s) and lands (flat areas - 0s ) on the surface of the disk.
- READING: a leaser beam is shone onto the surface. The amount of light reflected off the surface is detected by a light sensors and translated into 0s and 1s.
104
Give 2 examples of optical storage.
- CDs
- DVDs
105
What is solid storage?
A physical way of recording binary data. bits are represented by little pools of trapped electrons on a microchip.
106
How do you write and read data using solid storage?
- WRITING: control signals identify the pod to be written to and apply precise electrical charges, causing electrons to move between 2 pools. A higher voltage pulls more electrons which block the current flow. Blocked current flow is 0, current flow is 1.
- READING: control signals identify which bit is to be read and apply a small voltage. If the electron pool is empty, the transistor turns on and 1 is read. If the electron pool is full, the transistor doesn't turn on, and 0 is read.
107
Give 2 examples of solid storage?
- USB sticks
- SD cards
108
What is the main role of buses?
To transfer data.
109
When comparing data storage, what must you consider?
- Capacity
- Portability
- Speed
110
What is an embedded system, and what are its features?
A small computer designed to perform a specific function that must operate in real time.
Features:
- Small
- Cheap
- Limited functionality
- Customised hardware and software
111
What is a microcontroller?
Consists of a CPU, memory input/output ports and circuitry on a single chip.
112
What is a sensor?
Measures a physical quantity (e.g. temperature and light levels) to monitor changes in the environment.
113
Define flash memory.
Stores data and program instructions for the CPU to interpret and act on. It's non-volatile. It will continue to increase in capacity and decrease in size.
114
What is an actuator?
Converts the output commands from a microcontroller into a mechanical action.
115
List 3 products that have embedded systems.
- Washing machines
- Lighting
- Coffee machine
116
Give 2 embedded systems that are implanted in people's bodies.
- Pacemakers
- Cochlear implants
117
Why are embedded systems difficult to repair or upgrade?
Because they are hardware which may be fitted in a difficult to reach place when needing to replace the hardware.
118
What may some microcontrollers have?
- A timer
- A counter
- Some form of wireless connectivity
- An ADC (analogue to digital converter)
119
Define Wi-Fi.
Wireless network technology. A typical Wi-Fi signal can travel up to 100m at speeds of up to 10Gbps -> ideal for creating a WLAN.
120
What is Bluetooth?
Transmitting data through radio waves over short distances.
121
Define RFID.
Radio-frequency identification. It uses electromagnetic fields to identify and track tags attached to objects. A radio transmitter/receiver is embedded within each tag.
122
Define Zigbee.
Uses low-power radio waves to connect internet of things devices that have radio transmitters/receivers embedded within them.
123
What is the internet of things?
Wireless network tech that enables embedded system devices collecting and exchanging data with little or no human intervention.
124
What is a mesh network?
A network in which each device is connected to multiple other devices, either by cable or wirelessly.
125
What is power harvesting?
The process of extracting power from low levels of ambient energy in the environment, such as vibrations or light.
126
Define end-to-end security.
Data is encrypted so only the receiver can decrypt it, preventing 3rd parties from understanding it.
127
How does the Internet of Things work?
IoT devices use sensors to capture ambient data such as temperature, moisture levels, speed, light, vibrations and GPS location. Their microcontrollers analyse and process this data.
128
Give 3 examples of IoT systems.
- Microcontrollers
- Fitbit bracelets
- Infrared cameras and vehicle tracking sensors
129
Why is power consumption important to consider when designing IoT devices.
- Many IoT devices are situated in locations where they can't be physically connected to a power source.
- IoT devices also execute power-intensive activities
- It's important to keep power consumption to a minimum, so the need for charging is less.
130
Why is privacy and security a concern in IoT devices?
- IoT devices collect personal data by nature
- Manufactures of them pay little to no attention to secure them
- IoT devices are often shipped with an unchangeable default password
- Hackers, with one password, have access to all the devices sharing that password.
131
What is an operating system?
Controller and manager of:
- File management
- Process management
- Peripheral management
- User management
- Hardware
and all other software. It provides an interface for liveware (users).
132
Give some examples of OS.
Microsoft Windows, Linux, Android and iOS.
133
How does an OS manage processes?
- Extends main memory by creating virtual memory
- Scheduling algorithms to share processing time between processes
134
Define application software.
Programs or apps designed for end users.
135
Give 2 examples of application software.
- Web browser
- Console game
136
Define utility software.
Programs that add functionality to a computer system or improve its performance in some way.
137
Give 5 examples of utility software.
- File repair
- Backup
- Data compression
- Disk defragmentation
- Anti-malware
138
How does the OS keep track of files stored on a computer's secondary storage?
Hierarchal tree structure. Top node is the root directory (needs special access). Nodes below are directories, subdirectories or files.
139
What are directories and subdirectories?
Folders and sub-folders. They store files.
140
What are files?
Collections of related data. OS keeps track of info such as name, type and attributes.
141
How does the OS store files?
The OS splits the file up and places the smaller pieces into an empty sector. The start location and sequence numbers of each piece are kept track of for when the pieces need to be reassembled.
142
Which functions do the OS provide for users to manage files and directories?
- Save
- Open
- Copy
- Duplicate
- Rename
- Delete
143
Define sector.
Subdivision of a track on a disk, holding a fixed amount of data.
144
What are file permissions?
Controls who can access a file and what they're allowed to do with it. The permissions are read, write, execute and delete in ascending order.
145
What is a process?
Program loaded into main memory and is being executed.
146
Define scheduling algorithm.
Used to allocate each process running on a computer a share of the CPU's time.
147
Explain the first in, first out scheduling algorithm
Processes queue in the order they arrive. The process at the head of the queue uses the CPU until finished or waiting for another resource, such as a printer.
148
What are the advantages and disadvantages to the first in first out scheduling algorithm?
Advs:
- Low overhead, task switches only when process is completed
- Processes are never starved of CPU time
Disadvs:
- Throughput may be low as longer processes cause high wait time
- Response and completion times depend on the state of the queue
149
Define the shortest job first scheduling algorithm.
The process which is closest to finishing goes next.
150
What are the disadvantages and advantages of the shortest job first scheduling algorithm?
Advs:
- Low average wait time
- Responses for short processes are very fast
Disadvs:
- Longer processes are starved of processing time if many short processes are executed
- Execution time must be known first
151
Explain the round-robin scheduling algorithm.
Each process is assigned a time slice and processes must wait their turn. If unfinished, it goes to the back of the queue and waits again. Some high-priority processes get more time slices.
152
What are some advantages and disadvantages of the round-robin scheduling algorithm?
Advs:
- Balanced throughput
- Average response time is good, if number of process is low
Disadvs:
- Some overhead involved in switching between processes
- Processes may have to wait a long time to complete
153
What is virtual memory?
An area of secondary storage used by the OS to extend a computer's main memory.
154
What is a peripheral device?
A hardware device attached to a computer. Each one has its own device driver. Slow ones can slow things down in process management.
155
What do device drivers do??
Relays data between the OS and peripheral device.
156
Give the two types of UI.
- GUI with WIMP (Graphical User Interface with Windows, Icons, Menus and Pointers)
- CLI (Command-Line text Interface)
157
What is a superuser?
An administrator.
158
How is who can and can't use the computer managed?
Managed by the OS using passwords and biometric scanning.
159
How does file repair work?
The FR tool scans the damaged file and extracts as much data as it can, then stores it in a new, usable file.
160
How does backup work?
A backup tool can auto backup data stored on a computer hard drive to a network, drive, cloud etc. Good if a file is lost or damaged.
161
What is data compression?
Compresses file, reducing file size, freeing storage space and speeding up transfer across networks.
162
Define fragmentation.
Parts of a file are scattered across a disk rather than being stored sequentially. Issue for mechanical hard drives because read/write heads must move slower.
163
What is defragmentation?
The rearranging of files. All the parts of 1 file are consolidated, along with free space.
164
What is anti-malware?
Designed to eliminate malicious software from a computer.
165
Define corrupt file.
A file damaged in some way it can't be opened or read.
166
What is a cyberattack?
Any kind of malicious attack on a computer system or network with intent to cause damage or harm.
167
What is backup and recovery?
The process of creating backup copies of data and storing them in a separate location to the live working environment - possibly in the cloud - so that they can be recovered in the event of data loss or damage.
168
Define robust software.
Software capable of handling the unexpected without crashing, generating incorrect output or revealing sensitive data.
169
What is a code vulnerability?
A flaw in a program that compromises security which can be exploited by an attacker to gain access to a computer system, enabling them to steal or corrupt data, introduce malware or take over control of the computer for some purpose of their own.
170
What is a language specific vulnerability?
A known flaw in a programming language that can pose a threat to security.
171
Define hacker.
A seeker and exploiter of vulnerabilities in code in order to gain unauthorised access to a computer system or network.
172
What are code reviews?
Designed to sport instances of poor programming practice, find any vulnerabilities in the code and check its efficiency. There are 2 main types: review by another programmer and an automated review.
173
Define audit trail.
Reduces errors and improves accountability of changes.
174
What is an instruction set?
All instructions a CPU can execute.
175
What is machine code?
The binary code representing a program. Instructions are represented as binary code which makes up programs.
176
What is bare-metal programming?
Writing firmware (usually in C) that runs directly on the hardware.
177
Give some examples of high-level languages.
Python, Visual Basic and/or Java.
178
What is a translator, and what are the types?
A program that converts some code written in a high-level language into machine code. The two types are compilers and interpreters.
179
Define a compiler.
A translator that converts high-level language source code into machine code. The source code is translated all at once and saved as object code to be executed later. It's faster than an interpreter.
180
Define interpreter.
A translator that converts high-level language source code into machine code, one line at a time, whilst the program is being executed.
181
Give two types of low-level programming languages.
Machine code and assembly code.
182
What is assembly code?
Low-level language written using mnemonics. Each instruction has its machine code equivalent.
183
Define wired transmission media.
A wired transmission medium which connects computers and other devices in a network. Usually made of copper wire or fibre optic cable.
184
What is a UTP?
An unshielded twisted pair. It's the most common type of copper cable used to set up a LAN.
185
What is a fibre optic cable?
Consists of one or more very thin strands of glass, surrounded by several layers of protective material, encased in an outer sheath. It transmits data as pulses of light.
186
Define broadband.
A high-capacity transmission medium, capable of transmitting multiple signals and traffic types across long distances at high speeds.
187
What is FTTC?
Fibre to the Cabinet. A way to connect broadband via a mix of fibre-optic cable and copper cable.
188
What is FTTP?
Fibre to the Premises. A high-speed way to connect to broadband via a fibre-optic cable.
189
What is wireless transmission media?
Uses radio waves, microwaves or infrared waves to transmit data.
190
What is a WLAN?
Wireless local area network. Connected devices use high frequency radio waves to communicate.
191
Define router.
Manages communications on the network and can have a built-in wireless access point, enabling it to act as a gateway to the internet for all connected devices.
192
What is a wireless access point?
A networking device that enables wireless devices to connect to a router in order to access the internet.
193
Define internet.
The world's largest public WAN. It's a global system of interconnected networks linking together billions of digital devices worldwide.
194
What is a POP?
Point of presence. Local access point for an ISP. Network access points interconnect. It's the internet backbone around the world.
195
What is an ISP?
Internet Service Provider. An organisation that provides its customers with a connection to the internet.
196
Define eavesdrop.
Have unauthorised sight of data being sent from one computer to another over a network.
197
Define encrypted.
Prevents eavesdropping and interception through turning info into a form that only the intended recipient can decode, decrypt and read.
198
What is a NAP?
A Network Access Point. Interconnects the internet backbones to form a world-wide mesh network.
199
What is an IP address?
Internet Protocol address. Used to uniquely identify devices on a network. There are currently 2 versions: IPv4 and IPv6.
200
Define Internet Protocol.
Set of rules used to govern data transfer on the internet.
201
What is a network?
An arrangement of 2 ≤ computers that are connected together for the purpose of sharing resources and data. All types of computer (including IoT devices) can be linked together in networks.
202
Define VoIP.
A telephone connection over the internet in which voice signals are sent as packets of data.
203
What is a LAN?
A local area network that covers a relatively small area.
204
Define network manager.
Someone responsible for installing, configuring and maintaining the LAN of the organisation, supporting users and implementing appropriate backup and security measures.
205
Define WAN.
A Wide Area Network that spans multiple sites over a large geographical area, using a variety of transmission media to connect LANs together.
206
What is transmission media?
Cables, satellites, microwaves, etc. which connects LANs together. Transmits data between devices on a network.
207
Define speed of a network.
A measure of the performance which is measured in the bits per second, affected by bandwidth and latency.
208
What is bandwidth?
The capacity of a network (max volume of data that can be transferred per second). The bandwidth of modern high speed networks enables them to transmit billions of bits per second.
209
What is latency?
a.k.a. lag, the time between the data being transmitted and the moment it reaches its destination. Measured in ms. High latency = delay.
210
What is data transfer rate?
The speed at which data is transmitted from one device to another. Measured in bps.
211
How do you calculated the estimate of time for a file to be transmitted?
| (file transmission rate)
file size (bits) / network speed (bps) = time (s)
212
bps -> kbps -> mbps -> gbps conversion.
*1000
213
How do copper cables work and what is the range, speed, latency and usage of them?
- They transmit data as electrical pulses.
- They have a short range, up to 100m
- The speed is up to 10 Gbps
- High latency as copper is susceptible to interference and latency increases the further the signal travels
- It's used to connect computers and other devices on a LAN.
214
How do fibre optic cables work and what is the range, speed, latency and usage of them?
- Transmits data as pulses of light
- Long range, can transmit data over long distances with no loss of signal strength
- High speed, up to 100Gbps
- Low latency, data transmission is less subject to interference
- It's used to connect LANs together to form WANs and provide broadband services to private homes and businesses.
215
What is NFC?
Near field communication. Uses EM fields to create a high-speed connection between 2 devices in a very high proximity. The most common use is contactless payment systems.
216
Installation of wired networks vs. wireless ones.
Wired: time-consuming and disruptive
Wireless: Less time-consuming and disruptive as there as many many less cables.
217
Flexibility of wired networks vs. wireless ones.
Wired: No. of network access points and their locations have to be determined at the outset. Any changes require more/less cables.
Wireless: Very flexible, anyone with a wireless enabled device can access the network.
218
Range of wired networks vs. wireless ones.
Wired: Can transmit data over long distances and between different buildings on the same site
Wireless: Wi-Fi network has a theoretical range of 100m without physical objects and interference.
219
Bandwidth of wired networks vs. wireless ones.
Wired: Fast, up to 10 Gbps
Wireless: Standard Wi-Fi can transmit up to 3.2 Gbps; available bandwidth is shared by all active wireless devices.
220
Latency of wired networks vs. wireless ones.
Wired: Low
Wireless: High
221
Reliability of wired networks vs. wireless ones.
Wired: Consistent speed; less susceptible to interference.
Wireless: Inconsistent as Wi-Fi susceptible to interference.
222
Security of wired networks vs. wireless ones.
Wired: Data can only be accessed by devices that are physically attached to that network, so it is not easy to intercept or eavesdrop.
Wireless: Less secure -> data requires encryption.
223
What is the range, bandwidth, energy consumption and uses of Wi-Fi?
Range: 100m
Bandwidth: 3.2Gbps
Energy consumption: Very low
Uses: Portable devices
224
What is the range, bandwidth, energy consumption and uses of bluetooth?
Range: 10m
Bandwidth: 800Kbps
Energy consumption: Low-medium
Uses: Headphones, speakers, wireless keyboard & mouse
225
What is the range, bandwidth, energy consumption and uses of RFID?
Range: 450m
Bandwidth: 0.25MHz
Energy consumption: Low but increases the more readers collide
Uses: Security tags & ID cards
226
What is the range, bandwidth, energy consumption and uses of Zigbee?
Range: 20m
Bandwidth: 20Kbps
Energy consumption: very low
Uses: Home smart hubs, thermostats
227
What is the range, bandwidth, energy consumption and uses of NFCs?
Range: <20cm
Bandwidth: 400Kbps
Energy consumption: Very low
Uses: Smart cards, bank cards
228
Define node.
Each device on a network (PCs, server, printers, etc.)
229
What is a network topology?
The different ways nodes on a network connect to one another. The 3 common are bus, star and mesh.
230
Explain bus topology.
All nodes on the network are connected by a single cable. Messages are sent along the cable in the form of electronic signals. A terminator at each end absorbs signals that have reached the end of the cable, preventing them from bouncing back and causing interference.
231
Explain star topology.
Every node is directly connected to a central node, which is likely a switch. All data traffic passes through the central node, which is responsible for routing it to its destination.
232
Explain a mesh network.
Multiple nodes connected to multiple other nodes by cable or wirelessly. In a fully connected mesh network, every node is connected to every other node. In a partially connected mesh network, some nodes are connected to all nodes while others are only connected to 2 or 3.
233
What is a hybrid network?
Includes many individual networks with different topologies.
234
Define P2P.
Peer-to-peer. Data is transmitted between nodes (peers) on a network without the need for a network and a central controlling device.
235
What is an internet backbone?
Multiple cables, fibre optic links and satellites connecting countries and continents to each other. A main data route on the internet, owned and operated by a major telecommunications company.
236
What is hexadecimal in the context of IPv6 addresses.
Hexadecimal makes up an IPv6 address, as it is easier for humans to read.
237
Define static IP address.
An IP address which never changes, typically assigned to routers and servers (things that don't really move around much and require constant access to the network).
238
Define dynamic IP address.
An IP address assigned to a device by the network when they connect. When no longer needed, it is returned to a communal address pool to be given to a different device. If all addresses are taken, the new device must wait.
239
What is a DNS?
Domain Name System. Enables people to enter words instead of numbers for IP addresses. A directory of domain names and equivalent IP addresses.
240
Explain the process used to find the IP address of a website and download a page.
## Footnote
(*This was an exam question.*)
- Browser's URL is sent to the DNS server
- DNS server returns the web server's IP address
- The browser sends a HTTP GET request to the web server
- The web server returns a HTTP response
241
What is a DHCP?
A dynamic host configuration protocol, which is a network management protocol used to dynamically assign an IP address to any device (or node) on a network so it can communicate using IP.
242
What is a data packet?
What data is broken into to be sent across the internet. It's the small amount of data sent over a network with a header attached to it providing extra information including the source and destination address.
243
What does the header of a data packet include?
- IP address of source
- IP address of destination
- Sequence number of packet
- Total number of packets and checksum
244
What is packet switching?
A method of splitting data that is transmitted over a network into packets. Each packet is tagged with the IP address of the recipient and travels there independently. Then they are reassembled into the correct order upon arrival.
245
Define routing table.
A list of destinations and routes to get there. When a router receives a packet that needs to be forwarded on to another network, it uses the routing table to determine where to send it.
246
What is a TCP/IP?
Transmission Control Protocol/Internet Protocol. A 4-layered protocol stack that sets out exactly how data is to be formatted and transmitted across networks, including the internet.
247
What is a layered protocol stack?
A collection of protocols.
248
Define checksum.
An error detection technique; a mathematical formula is applied to the data and the resulting the checksum is transmitted with the data. The recipient computer applies the same formula to the received data. The resulting checksums should match. If they don't, the data has been corrupted.
249
Explain the process of packet switching.
1. A router is the path a packet takes when it travels from its source to its destination.
2. Each router works independently to move the packet one step further along.
3. The router uses its routing table to move the packet one step.
4. A routing table stores the routes to other network destinations, including its direct connections.
5. Packets are sent outside local networks when the network portion of the IP address is different from its own.
6. Routers don't know the contents of the other routers' tables.
250
List the layers on the TCP/IP protocol.
- Application layer
- Transport layer
- Internet layer (network layer)
- Link layer (network interface layer)
251
What is the application layer of TCP/IP protocol?
Defines how various user services operate, such as web browsers and email.
252
What is the transport layer of TCP/IP protocol?
Establishes a dedicated channel between the source and destination devices to transfer the data along.
It also determines how outgoing data is split up into packets and how incoming packets are reassembled.
Doesn't know what the data represents.
253
What is the internet layer of TCP/IP protocol?
Adds the source and destination IP address to the data packets received from the transport layer and routes them to the recipient.
254
What is the link layer of TCP/IP protocol?
Defines how data is transferred from one device to another along the whole route from sender to recipient.
On a wired network, it defines how:
- the network card in the sending computer transmits them to the router
- the router transmits them to the modern
- the modern transmits them to the green cabinet in the street
On a wireless network, it defines how:
- the Wi-Fi chip in the computer transmits data to the router
255
List the protocols linked to each layer of the TCP/IP protocols.
Application layer: HTTP, HTTPS, FTP, SMTP, POP3, IMAP
Transport layer: TCP
Internet layer: IP
Link layer: Ethernet, Wi-Fi
256
What happens to each layer when computer A sends data to computer B?
Comp A sends data -> A app layer -> A trans layer -> A int layer -> A link layer -> B link layer -> B int layer -> B trans layer -> B app layer -> Comp B receives data
257
What is the difference between POP and IMAP?
In IMAP, unlike POP, the messages don't have to be downloaded. They can be read and stored on the message server.
258
Define network security.
The protection of a network from external and internal threats such as viruses, hacker attacks, data interception and theft, etc.
259
Define security threats.
An incident - malicious or unintended - that causes disruption, damage or data loss.
260
What is a virus?
A piece of malicious code that attaches itself to a legitimate program and is activated when the 'host' program is on, it can cause severe damage to data.
261
What is ransomware?
An attack on a network in which data stored on a server is encrypted, making it unreadable. The victim must pay a ransom to get the data unlocked.
262
Define data integrity.
The reliability and trustworthiness of data.
263
What is a DOS attack?
A denial-of-service attack. An attack on a network that attempts to prevent legitimate users from accessing its services.
264
What is ethical hacking?
a.k.a. "Good" hacking, looking for weaknesses in software and systems so that they can be addressed.
265
Define penetration testing.
'Pen testing' is the uncovering of vulnerabilities that could be exploited by a criminal by an ethical hacker (white-hat hackers).
266
What is social engineering?
An attack that exploits how people behave and respond to certain situations in order to trick them into revealing personal information, usually used by an ethical hacker to test how easily tricked legitimate users of the network can be.
267
List the 3 important principles underpinning data security.
- Confidentiality
- Correctness
- Availability
268
What is access control?
Control of who can log into a network and determines what legitimate/authorised users can see and do on the network.
269
Define authentication.
The process of checking the identity of an individual attempting to gain access to a network.
270
Define multifactor authentication.
To provide an extra level of security, a user must provide a piece of knowledge, a physical artifact and a physical attribute.
271
What is the principle of least privilege?
Employees are only given the permissions and administrative rights they need to do their job.
272
Define physical security.
Controlling access to critical parts of a network using physical method rather than software.
273
What is malware?
Software that has been designed to gain unauthorised access to a computer system in order to cause damage, disrupt its functioning or collect information without the user's knowledge
274
Define firewall.
A network security system that acts as a barrier between an organisations internal network and the internet. It inspects incoming and outgoing data traffic and uses a set of rules to decide what data to allow through from one side to the other.
275
What is encryption?
A technique which scrambles any data into an unreadable form to anyone who doesn't have the key to turn it back into its unscrambled form. This is useful for when we send sensitive information, so it can't be understood. There's 2 types: asymmetric and symmetric.
276
List three criteria that a user must provide to gain access to a network using a multifactor authentication.
- A piece of knowledge such as an ID, password or pin
- A physical object such as an identity pass
- A physical attribute such as fingerprint or voice
277
Give 3 examples of authentication.
Username and password, algorithms and code and multifactor authentication.
278
Define a digital device.
Smartphones, tablets, embedded systems, e.g.
279
What is e-waste?
Any form of discarded electronic equipment, including digital devices.
280
What is a precious metal?
Very rare, naturally occurring, metallic elements of high economic value.
281
Define semiconductor.
Present in every piece of computing technology, it's a substance (solid element or compound) used to make computer chips. It can conduct electricity under some conditions but not others, making it a good medium for the control of an electrical current.
282
What is the replacement cycle?
The period of time between the purchase of assets and their replacement with equivalent assets.
283
Define carbon footprint.
The amount of CO2 an individual or organisation produces as a result of the energy they consume.
284
What is cloud computing?
The storing of software and data on remote servers accessed through the internet.
285
Give 2 reasons why the disposal of e-waste represents a threat to the environment.
- E-waste can include hazardous materials that leak out toxic substances, contaminating water supplies, infiltrating the food chain and polluting the air.
- Large amounts of e-waste are shipped overseas to developing countries, where it's dumped into landfill sites or dismantles to extract the minerals.
286
What are WEEE regulations?
The Waste Electrical and Electronic regulation's main aim is to set targets for the collection, recycling and recovery of computing technology and other electronic devices. They apply to businesses, but not individuals.
287
What is the ROHS directive?
The EU Restriction of Hazardous Substances directive we brought into the UK law in 2013, restricting the use of all six toxic materials, forcing manufacturers of computing tech to replace them with safer materials.
288
Why can cloud computing affect the environment?
Cloud computing and storage of vast amounts of data on remote servers has led to the building of data centres around the world. These store all images, tweets and selfies generated by social networking.
289
Give 3 ways we can make data centres more efficient.
- Using hot-aisle/cold-aisle configuration to increase cooling system efficiency, using blanking panels to minimise recirculation of hot hair and sealing the floor to prevent cooling losses.
- Investing in research to develop a new, less energy hungry alternative
- Ration internet usage - possibly through tax on uploading data and/or educate users so they behave in a more environmentally responsible fashion
290
What is personal data?
Any information relating to an identifier/identifiable living person. This includes name, age, gender and location.
291
What is identity theft?
The stealing of another person's personal details or passport number.
292
Define identity fraud.
Making purchases and running up debts in someone else's name.
293
What is GDPR?
The General Data Protection Regulation data protection laws in the UK are based off of. It contains the 99 articles setting out the right of individuals and the obligations of organisations who collect, process and store data.
294
Define a data subject.
A person whose data is being collected and processed.
295
What is a data breach?
A breach of security leading to the accidental or unlawful destruction, loss, alteration, unauthorised disclosure of, or access to personal data.
296
Give 4 legal responsibilities of data holders.
- The data must be processed in a fair, lawful and transparent manner.
- The data should be accurate and up-to-date.
- The data must not be kept longer than necessary.
- The data subjects must give their consent - they must be asked to opt in or out.
297
Give 4 legal rights of data subjects.
- They must be informed about the collection and use of their data.
- They have the right to have their data erased.
- They have the right to restrict or stop the processing of their data.
- They have the right of data portability, meaning they can move, copy or transfer the data.
298
List and explain 3 types of offences in the Computer Misuse Act of 1990.
- Unauthorised access to computer material; using a computer to attempt to access a program or data to which you know you are not authorised. The attempt itself is an offence, successful or not.
- Unauthorised access with intent to commit further offences; to attempt to access a computer system with the intention of committing a further offence.
- Intentional and unauthorised destruction of software or data; to gain unauthorised access to a computer with the intention to change the data or impair the running of the computer.
299
Define robotics.
The design, construction, operation and use of robots.
300
What is AI?
Artificial Intelligence. Machines and their programs that solve problems commonly associated with human intelligence, e.g. learning, problem-solving and pattern recognition. Can be used in smartphones, surveillance, etc.
301
Define LAWS?
Lethal Autonomous Weapons. They can search for and engage targets on their own, making their own decisions with direct human control.
302
What is machine learning?
The branch of AI that allows them to learn independently. It's used by music and video streaming services to make recommendations.
303
One ethical concern of surveillance cameras.
Surveillance cameras can use face recognition to identify individuals. Concern: personal data that is being collected without permission of those being captured.
304
What is a signature?
Known malware definitions allowing it to be identified.
305
Define heuristics.
Identifies malware by behaviour and characterisation instead of comparing against a known list of malware. It's a set of rules used to detect malicious behaviour without having to uniquely identify the program responsible for it.
306
Give 3 heuristics rules.
- A program which tries to copy itself into other programs
- A program which tries to write directly on the disk
- A program which decrypts itself when run
307
What is asymmetric encryption?
Encrypts and decrypts data using 2 different keys, a public key and a private key. Every user has both. A message encrypted with a specific public key, which can only be decrypted by the corresponding private key.
308
What is symmetric encryption?
It has algorithms to encrypt and decrypt a message using the same key. Both ends of the transmission must know the exact same shared key.
309
Why does antimalware need to be regularly updated?
Because new malware may've been created and distributed, meaning the out-of-date antimalware won't have the signature of the new malware in its database. Therefore, the infection goes unidentified and the antimalware fails to protect the computer.
310
Define plain text.
The readable content before it's encrypted or once it has been decrypted. Cipher text is encrypted plain text.
311
What is an acceptable use policy?
A set of conditions or rules that a network user must agree to comply with before they're allowed to use the network.
312
What should an acceptable use policy have?
- Rules that ensure all laws are complied with
- Rules that ensure no software is installed, so the network isn't harmed in any way.
- Rules that ensure no files from the internet are downloaded; making sure the network security isn't jeopardised.
313
Define a backup network policy.
A policy which ensures the copying of programs and data stored on the network to safeguard them in case of natural or man-made distasters.
314
What could a backup network policy have?
- Who's responsible for the backup process
- When the backup is to be made
- Where the backups will be kept
- How long the backups will be kept
315
Define a recovery policy.
A set of procedures that the organisation will follow to restore normal system operations if there's a natural disaster or a man-made one.
316
What could a recovery policy include?
- How often it should be tested
- A statement of where all the data backups are kept
- A description of where all data backups are kept
- A description of which data should be restored and in which order it should be restored in
317
How do you initialise a variable? (with examples)
You must assign it a valid value.
integer -> 0
float -> 0.0
string -> ""
boolean -> FALSE (or true depending on the coe)
318
What are the flowchart symbols?
- start/end: (__)
- process to be carried out [___]
- decision to be made <_>
- input or output /__/
- shows logical flow of the algorithm ->
- pre-defined subprogram (_|___|_)
319
List the declaration keywords for each data type.
Int (integer), float (real), bool (boolean), str (string).
320
What is coercion vs. conversion.
- Coercion: Automatic data type change
- Conversion: manually written conversion that explicitly causes change in data type, e.g. int/str/bool/float()
321
Define index.
An integer number denoting the position of a single item inside a larger collection. Indices is the plural of index. Indices start at 0.
322
What is concatenation?
The joining together of 2 or more items of information. Concatenating 2 strings produces a new string.
323
Define a data structure and list the 4 types.
An organised collection of related elements. The types are strings, arrays, records and lists.
324
What is a one dimensional data structure?
Data structure with elements that are arranged in one direction only.
325
Define an array.
A collection of related elements that share a single identifier name and one of the same data type.
326
What is a record?
A collection of related elements of different data types; each element is known as a field.
327
What's the difference between local and global variables?
Local variables are inside subprograms, global variables are outside subprograms.
328
What is a subprogram, and what are the 2 types?
Subprograms are blocks of code that perform a specific type. The two types are procedures and functions.
329
What is a subprogram call?
The mechanism that causes the code inside a subprogram to execute.
330
What is the difference between procedures and functions?
Procedures don't return a value, functions do.
331
Define repetition construct.
A loop which is repeated until a condition is met. Used when the number of times a loop must be repeated is unknown.
332
What is a while construct?
Allows a group of instructions to be repeated over and over as long as a test condition is true.
333
Define precedence.
The default order in which mathematical operations are carried out, for logical operators the order is (), not, and, or.
334
What is a while statement?
The keyword 'while' allows a group of instructions to be repeated over and over as long as the test conditions are true.
335
How to improve code readability?
You can use brackets, comments, descriptive names, indentation and white-space.
336
Define nested loop.
A loop within a loop. Every time the outer loop has an iteration, the inner one must too, but not vice versa.
337
What is an argument?
Pieces of data provided as input to a function.
338
What is a field?
Each element known in a record.
339
What is a list?
The way python can be used to implement the concepts of an array and record.
340
Define iteration.
Loop type used when processing every item in a data structure one after the other; the amount of times the loop will loop must be known.
341
What is a FOR EACH construct?
Loop that executes a set number of times. The number of times it'll execute is based on the size of the data structure.
342
Define a FOR EACH statement.
Looping construct, using python keyword 'for', that executes a fixed number of times based on their size of data provided in the statement.
343
What is a FOR IN RANGE construct?
Loop that executes a fixed number of times which is known before the loop starts.
344
Define FOR IN RANGE statement.
Looping construct, using python keyword 'for...in range()', executes fixed number of times. Number of times is known before loop starts.
345
How do you declare and initialise a data structure?
Declaration: variableName = [] or variableName = list()
Initialisation: variableName = ["sever", "the", "blight"]
346
What is a FOR construct?
Name given to a group of constructs used to implement iteration.
347
How do you calculate the index of the last item in a data structure?
[len(variableName)-1]
348
Define built-in in the context of subprograms.
Subprograms that are provided in most high-level programming languages to perform very specific common tasks.
349
What is a function?
A subprogram which performs a specific task that can be used at any time that returns a value to the calling program.
350
What is a procedure?
Contains a set of statements that are executed when the procedure is called; no value is returned to the calling program.
351
Define scope.
A region of code within which a variable is visible.
352
Define library.
A collection of self-contained named block of code that can be called upon to do work when needed.
353
What is a parameter?
Values that are passed into a subprogram when it is called.
354
Define dry run.
A technique used to help programmers understand a program, find its purpose, checks for logic errors and ensure it's working correctly. To do one, you need to execute lines of code with some input data as if you were the computer.
355
What is an infinite loop?
A loop that's never-ending, since the condition required to terminate the loop is never reached.
