IGCSE Flashcards
(167 cards)
1
Q
6.2 robotics
A
branch of computer science that incorporates the design, construction and operation of robots
(e.g. factory equipment, domestic robots, drones)
2
Q
6.2 Characteristics of a robot
A
mechanical structure of framework, electrical components (e.g. sensors, mp, actuators), programmable
3
Q
6.3 AI
A
artificial intelligence
: branch of computer science dealing with the simulation of intelligent behaviours by computers
4
Q
1.2 Resolution
A
number of pixels wide by number of pixels high
5
Q
1.2 colour depth
A
number of bits used to represent each colour
6
Q
1.2 image
A
series of pixels that are converted to binary, which is processed by a computer
7
Q
2.1 structure of a packet
A
packet header, payload, trailer
header –> destination address, packet number, originator’s address
8
Q
2.1 process of packet switching
A
data broken down into packets
each packet could take a different route
router controls the route a packet takes
packets may arrive out of order
once the last packet has arrived, packets are reordered
9
Q
Serial data transmission
A
one bit at a time // using a single wire
10
Q
parallel
A
several bits transmitted at the same time // down a several wires
11
Q
simplex
A
data sent in one direction only
12
Q
half-duplex
A
sent in both directions // only one direction at a time
13
Q
full-duplex / duplex
A
data transmitted in both directions at the same time
14
Q
3.1 Microprocessor
A
type of integrated circuit on a single chip
15
Q
3.4 Computer needs a ____ to access a network
A
NIC (network interface card)
16
Q
3.4 Role of router in a network
A
sends data to a specific destination on a network, assign IP addresses, connect a local network to the internet
17
Q
5.1 URL
A
uniform resource locator.
text-based address for a web page; can contain the protocol, domain name, web page/file name
18
Q
5.1 purpose of a web browser
A
display webpages
by rendering hypertext markup language (HTML)
19
Q
5.1 functions of a web browser
A
− Convert HTML code
− Display web pages
− Check if a website is secure
− Request web pages from a web server
− Send URL/domain name
− Runs active script
− Store history/favourites/bookmarks
− Create tabs
storing bookmarks/favourites, recording user history, allowing use of multiple tabs, providing an address bar, providing navigation tools, send URL to DNS, managing protocols
20
Q
1.3 Data storage units
A
bit - nibble - byte - kibibyte - mebibyte - gibibyte - tebibyte - pebibyte - exbibyte
21
Q
impact of data compression
A
less bandwidth required, less storage space required, shorter transmission time
22
Q
Sample rate
A
number of samples taken in a second
23
Q
sample resolution
A
number of bits per sample
24
Q
Increasing sample rate & resolution would..
A
increase the accuracy of recording and file size
25
byte = _ bit
8
26
Increasing the resolution & colour depth will..
increase the file size & quality of image
27
How are files compressed using lossy
compression algorithm used
redundant data removed
reduce colour depth, image resolution, sample rate, sample resolution, frame rate
reduces sample rate, sample resolution
reduces file size by permanently removing data
28
how are files compressed using lossless
for images and text
reduces file size without permanent loss of data
original file can be restored
compression algorithm used
example : run length encoding - RLE
repeating frames/pixels identified // collated/indexed // no data is permanently removed // just records the changes between frames
repeated words identified // are indexed // replaced with their index // their positions are stored // number of occurrences stored
29
Role of CPU
process instructions and data that are input into the computer so that the result can be output
processes data // processes instructions // carries out calculations // carries out logical operations // fetch ,decode, execute
30
Process of the fetch-decode-execute cycle
PC holds address of next instruction to be fetched// address sent to MAR // using address bus // PC is incremented // instruction is sent from address in memory to MDR // instruction is transferred using data bus // instruction sent to CIR
31
Instruction set
list of all the commands that can be processed by a CPU and the commands are machine code
32
What is meant by a MAC address?
Media access control
UNIQUE address // used to identify a device // does not change // set by a manufacturer // first part : manufacturer ID // second part : serial number
33
uses of hexadecimal
error messages, IP(v6) address, assembly language, HTML colour codes, URL, ASCII.Unicode
34
DDoS attack. and it's method of prevention
attacker encourages people to download malware onto their computer
turn each computer into a bot creating a network called a bot net
multiple computers are used as bots // designed to deny people access to a website // large number of requests sent to a server // all at the same time // server is unable to respond // the server fails
prevent - Firewall OR proxy server
35
characteristics of IP address
unique address // can be static or dynamic // can be public or private // can be IPv6 // can be IPv4
36
network component that uses IP address to send data only to its correct destination
router
37
purpose of CU
send control signals // that manage the transfer/flow of data & instructions within the CPU
decodes an instruction // using an instruction set // manages the execution of instructions in CPU
38
purpose of core in a CPU
process an instruction // carry out a fetch-execute cycle
increasing core may increase perforance, because more instructions can be processed simulaneously
39
Advantages of high-level language
easier.quicker to read/write/understand - less chance of mistakes
greater range of languages
easier to maintain
easier to debug
-> can find and correct errors in less time
code is portable
40
disadvantages of high-level language
not able to directly manipulate the hardware // may need to wait for translation before running // program may be less efficient
41
IDE (integrated development environment) , and it's functions
software that provides useful functions for a programmer writing a computer program
code editor, run-time environment, translators, error diagnostics, auto-completion, auto-correction, prettyprint
42
character set
all the characters and symbols that can be represented by a computer system // each character & symbol assigned a unique value
43
secure socket layer (SSL)
is a security protocol // encrypts any data that is sent // uses digital certificates // which are sent to user's browser // that contains the ___'s public key // that can be used to authenticate the ____ // once the certificate is authenticated, the transaction will begin
− Uses (digital) certificates
− ….requested from web server by browser/client // browser/client asks web
server to identify itself
− Server send SSL/digital signature to browser/client
− Client and server agree on encryption method to use
− … that contains the server's public key
− Browser checks authenticity of certificate…
− … then session key is generated
− … the transaction will begin // sends signal to server to start transmission
44
what is meant by ROM
read only memory// non-volatile memory // primary storage // holds firmware // cannot be written to
45
phishing
legitimate looking emails sent // encourages user to click link // redirects to a fake website // aim is to obtain personal details
46
pharming
malicious code is downloaded without user's knowledge // that will re-direct user to fake website // encourages to enter personal details into a fake website
47
brute-force attack
Trial and error to guess a password //
Combinations are repeatedly entered // until correct password is found //
Can be carried out manually or automatically by software
48
hacking
gaining UNAUTHORISED ACCESS to the computer
steal data file that contains personal details
49
malware (include types of malware)
virus, worm, trojan horse, spyware, adware, ransomware
email sent to user to encourage them to click link/download attachment // triggers download of malware/virus
50
social engineering
Manipulating / deceiving / tricking people ///// to obtain data // to force them to make an error
e.g. phishing
51
how does encryption improve data security
encrypted text is meaningless// need the key to decrypt the text
52
what is meant by interrupt
signal sent from a device // requests processor time // interrupts have different priorities
53
benefits of touch screen
does not require peripherals // less chance of input error // number of possible inputs limited
54
what is meant by HTML structure & presentation
and examples of it
structure : layout of the web page ,
e.g. placement of text, margins, line break, padding, heading, subheading
presentation : formatting of the web page ,
e.g. font colour, font style, font size, image size, background colour
55
why are structure & presentation often separated
FORMATTING of the page can be edited WITHOUT NEEDING TO ALTER THE STRUCTURE // so they can make regular updates without needing to check the structure
FORMATTING document can be used again for a different website // if further content are added to website, necessary formatting can be easily applied // this can save time when developing a website
can easily change the style of webpage
can add new content and apply same style easily
can re-use presentation for other websites
56
browser
SOFTWARE/APPLICATION that allows users to view webpages / render HTML
57
ISP internet service provider
company that provides a user with a connection to the internet
58
HTTP // HTTPS
hypertext transfer protocol secure ------ secure protocol that is used to send data for web pages across the internet // set of rules for data transmission // combines HTTP and SSL to transmit data // encrypts data for transmission
59
cookie
small text FILEs // stored by the browser // that contains data about a USER'S BROWSING HABITS/DETAILS/PREFERENCES
sent between web SERVER and BROWSER when user visits the website.
60
firewalls
set criteria // such as a whitelist/blacklist // firewall examine the INCOMING & OUTGOING traffic // check whether traffic meets criteria // if data is sent that is not on the list, it will be blocked.rejected
prevents hacking
61
What is meant by a high-level language
uses English-like statements , close to human language // needs to be converted to MACHINE CODE // using a translator // it is portable // one line of code can perform multiple commands
machine independent,
62
examples of data damage and it's prevention method
software failure -- enable automatic updates
hardware failure -- correct care & maintenance of hardware
fire -- keep device in a fireproof box when not in use
water -- don't have water near the device
data accidentally deleted -- add verification method for data deletion
back data up, use surge protection, don't drink liquids near a computer
63
examples of optical data storage
CD, DVD, blu-ray
64
what is meant by HTML
hypertext mark-up language
used to create webpages
65
uses / functions of cookies
saving personal details --> no need to be re-entered // tracking user preferences -> can send adverts that match their preferences // holding items in an online shopping cart // storing login details
66
role of arithmetic logic unit
carries out calculations // carries out logical operations // holds temporary values during calculations // temporarily store data // in a register called the accumulator
67
functions of operating system
managing files // interrupt handling // managing user accounts // managing peripherals // multitasking // providing an interface // installs software // memory management
68
how are data encrypted
encryption algorithm is used // to scramble data // original data called plain text // key is used to encrypt the data // key applied to plain text // plaint text encrypted into cypher text
key is transmitted separately // key is used to decrypt the cypher text
69
spyware
The user receives an email with an attachment/link containing the spyware // user clicks a link on an untrusted website // spyware downloaded onto the user’s computer // spyware records all the key logs from the user’s keyboard // recorded key logs sent back to the creator of the spyware // key logs analysed // A common pattern/word in the key logs allows a password to be identified
70
what is meant by primary storage
memory directly accessed by the CPU // example : RAM,ROM // RAM stores data&programs that are currently in use, ROM permanently stores boot-up instructions // RAM : volatile, ROM : non-volatile
71
what is meant by secondary storage
storage that is not directly accessed by CPU // example : HDD,SDD // stores data,files that can be accessed at a later stage // non-volatile
72
how does compiler translate a computer program and report errors
translates high-level language into machine code // translates all at once before executing // produces an executable file
creates an error report after trying to compile // displaying all errors // require correction before execution can take place
73
how does interpreter translate a computer program
translates high-level language to machine code // translates line by line // stops execution when an error is found // will only continue when error is fixed
74
what is an assembly language
form of low-level language that uses mnemonics.
assembler is needed to translate an assembly language program into machine code.
75
what is meant by https
hypertext transfer protocol secure // means the website uses SSL // means data sent is encrypted
76
proxy server
acts as a firewall // monitor/examines incoming AND outgoing traffic // rules for traffic can be set // blacklist/whitelist set // blocks any traffic that does not meet criteria // can send a warning message to the user // stop the website failing in a Dos attack
prevents direct access to the WEBSERVER // if an attack is launched it hits the proxy server instead // used to direct invalid traffic away from the webserver // filter traffic // if traffic is valid, data will be obtained by the user // if traffic is invalid, request to obtain data is declined // can block requests from certain IP addresses
limits the number of requests to the website // preventing too many requests that could overwhelm the server // block multiple requests from the same IP within a timeframe
help prevent ddos, act as a firewall, reduce the number of requests server needs to process, allow faster response time for requests
77
examples of robotics
factory equipment, domestic robots, drones
78
role of web browser in requesting&displaying web pages for the website
sends request to webserver // receives web pages back from webserver // converts HTML to display web page // manages protocols
79
purpose of RAM
store data currently in use
80
purpose of ROM
permanently store the boot up instructions
81
purpose of HDD
store the database / software
82
virus
software that can replicate itself // cause the computer to crash // could delete,damage files // could fill up the storage space // could spread to other devices on the network
83
how does a browser check that a website is secure
requests web server to identify SSL certificate // receives a copy of a certificate, sent from the web server // checks if certificate is authentic // sends signal back to webserver that it is authentic // starts to transmit data once connection is established as secure
84
symmetric encryption
data is ENCRYPTED and DECRYPTED using the SAME key// if hacker gains access to the key, they can decrypt intercepted information
data before encryption : plain text
data after encryption : cypher text
key is sent to a receiver
85
asymmetric encryption
uses public & private key . both keys are needed to encrypt and decrypt
86
IP address
internet protocol .
UNIQUE address // used to identify and locate devices on the internet // can be static or dynamic // IPv4 has four groups of digits // IPv6 has eight groups of digits // can be public or private
87
what is meant by low-level language
close to language processed by computers // may use mnemonics // example : assembly language, machine code
machine dependent, have direct access to memory locations, may need an assembler to be translated, one line of code represents a single instruction
88
advantages of low-level language
quicker to execute // can directly manipulate the hardware --> more efficient control // program will be more memory efficient // no requirement for a compiler.interpreter // allows the use of specialised hardware
89
concept of digital currency
ONLY exists electronically // decentralised // volatile // example : bitcoin
can be a decentralised system // can be a centralised system // usually encrypted
90
definition of digital currency
currency that exists only in electronic form
91
process of blockchain
acts as a ledger // by tracking each transaction // keeps a series of time-stamped records // that cannot be altered
92
difference between application software & system software
system - provides services that the computer requires (operating system, utility software)
application - provides services that the user requires
93
How captured images are converted to digital photo files
– Image is converted from analogue to digital (using ADC)
– Image is turned into pixels
– Each pixel is given a binary value
– Pixels form a grid (to create the image)
– Each pixel has a colour
– Pixels are stored in sequence (in a file)
– Meta data is stored (to describe the dimensions/resolution of the image) // It stores the dimensions/colour
depth .etc.
– An example of a suitable photo file format e.g. JPEG
94
checksum
– checksum value is calculated FROM THE data
--using an algorithm
- value appended to the data
– (checksum/calculated) value transmitted with data
– receiver recalculates the checksum value
- value compared to the transmitted checksum after transmission
– If they are the same then no error-successful transmission, otherwise an error has occurred
95
ARQ
– uses positive/negative acknowledgment and timeout
-- sender starts a timer when data (packet) is transmitted
-- receiving device checks data packet for errors
-- once they know the packet is error free it sends an acknowledgement back to the sending device
-- next packet is sent
– A request is sent with data to acknowledge all data is received
– Acknowledgement sent back to say all data is received
-- if no error detected, positive acknowledgement is returned to sender
-- if error detected, negative returned to sender
-- triggers the data to be resent
– If no acknowledgement is received in a time frame data TINMEOUT OCCURS, data packet is automatically resent.
-- until an acknowledgement is received
96
optical storage - how is laser used to store and read data from the disk?
Laser is shone at the disk
An (arm/head) moves the laser across the surface of the disk
The laser burns pits onto the surface of the disk
The laser is used to read the pits and lands on the surface of the disk
The reflected light from the laser shining on the disk is captured (by a sensor)
97
advantages of SSD
small in size, low power consumption, fast access speed, runs quietly, runs at cool temp, high capacity
98
why computer can only process binary data
Computer consist of transistors / logic circuits/gates …
… that can only store/process data in two states / high-low / on-off / 1 and 0
99
benefits of USB
− universal standard
− can’t be inserted the wrong way around/incorrectly
− Supports different transmission speeds
− Automatically detects device
-- fast transmission speed
-- backward compatible
--
100
Role of program counter
holds the address of the NEXT/CURRENT INSTRUCTION to be processed
101
role of MAR
holds the address of the data that needs to be fetched / address where the data needs to be stored
102
role of MDR
TEMPORARILY store // address of next instructions required // stores address that is to be collected by the address bus
stores data THAT IS IN USE // from address in MAR
103
role of CIR
stores the instruction of CPU currently decoding or executing
104
role of accumulator
built into ALU, temporary holds the result of interim calculation
105
drawback of using LOSSY compression
reduced quality, original file cannot be reconstructed
106
drawback of using LOSSLESS
takes more time to transmit file // larger file size -> takes up more storage space // data usage would be increased // uses more bandwidth -> could be more expensive
107
what is stored in primary storage
BIOS // start-up instructions // programs currently in use // data currently in use // parts of OS currently in use
108
why are both checksum & ARQ used
checksum used to detect errors // using a calculated value
ARQ checks if data is received // uses acknowledgement and timeout
requests data be sent again if checksum detects error
109
how are webpages requested and displayed
Brower sends URL to DNS // using HTTP(S) // DNS finds matching IP addresses for URL // DNS returns IP address to the browser // browser sends request to web server // web server sends web pages back to browser // browser RENDERS HTML to display webpages // security certificates exchanged // encrypting any data sent
110
why might a error not be detected using parity check
transposition of bits // does not check the order of bits // even number of bits change // incorrect bits still add up to correct parity
111
disadv of parallel data transmission
bits may arrive skewed // more expensive to setup // limited distance // more prone to error
112
adv of using hexadeciaml
easier to understand // easier to debug // takes up less screen space,display // less chance of making an error
113
operation of USB flash memory
data flashed onto chips // uses NAD/NOR technology // uses transistors // to control the flow of electrons // type of EEPROM tech // when data stored, transistor is converted from 1 to 0 // writes sequentially
114
how are cookies used
webserver sends cookie file to user's browser // user's data (payment details) stored in encrypted text file // cookie file is stored by browser // when revisit website, webserver requests cookie file // and broswer sends cookie file back to webserver
115
concerns of cookies
user does not see what info is stored // feel privacy is affected
profile could be built about the user // lead to identity theft
sensitive info stored could be intercepted in transmission // other websites could gain access to stored cookies // so payment info could be stolen and used by a third party
116
operation of HDD
− It has platters
− Platters/disk divided into tracks
− Platter/disk is spun
− Has a read/write arm that moves across storage media
− Read/writes data using electromagnets
− Uses magnetic fields to control magnetic dots of data
− Magnetic field determines binary value
117
parity check
odd or even parity is SET for the data
number of 1s/0s counted
parity bit is added to each byte before transmission
to make the sum of the bits in each byte odd/even
after transmission, if the number is __ no error detected
after transmission, if the number is ___ error is detected
118
why are lossy > lossless
decreases file size more
quicker to upload.download
takes up less bandwidth to upload
less lag
uses less data allowance
119
three types of bus
Address = unidirectional
data = bidirectional
control = bidirectional
120
components of expert system
knowledge base, rule base, inference engine, interface
121
operation of expert system
has an interface // used to input data // has a knowledge base // has a rule base // has an inference engine // applies rule base to provide output // decides what to ask next based on the data input
122
how is text converted to binary to be processed by the computer
character set is used
such as ASCII/unicode
each character has a unique binary value
123
what is meant by cloud storage
A collection of servers // that store data in a remote location // that allows data to be accessed remotely // that are (normally) accessed using an internet connection
124
disadvantages of storing in cloud storage
May be less secure // May lose access to them if internet connection lost // Reliant on a third party maintaining the hardware // Could incur an extra/ongoing fee/cost
125
network interface card definition
this is a component in a device that enables it to connect to a network
126
router definition
device that forwards packets to their correct destinations in a network
127
how to avoid pharming
Checking the spelling and tone of the email/website
Checking the URL attached to a link
Scanning a download with anti-malware
Only downloading data / software from trusted sources
Never providing personal details online
Install a firewall to check if the website is valid
128
access levels
Providing users with different permission for the data
Limiting access to reading data limiting the data that can be viewed
Limiting access to editing data // limiting the data that can be deleted / changed
Normally linked to a username
129
advantages of serial data transmission, not parallel
More accurate/reliable/efficient over long distances
− Less chance of interference / cross talk
− …that will skew / distort the data // less likely to get errors
− Data will arrive in order
− Serial is cheaper to purchase/install/maintain
130
why are interrupts needed
− To identify that the processor's attention is required // to stop the current
process/task
− To allow multitasking
− To allow for efficient processing // prioritising actions
− To allow for efficient use of hardware
− To allow time-sensitive requests to be dealt with
− To avoid the need to poll devices
131
how digital image file is stored
* Image is made of pixels
* Each pixel stores one colour
* Image has a set number of pixels wide by pixels high
* Each colour has a unique binary value // Each colour has a unique colour code
* The colour/binary value of each pixel is stored in sequence
* File contains metadata to identify how the file should be displayed
* … metadata can be the colour depth / resolution
132
how parity bit is used
parity can be set to odd or even // sender and receiver agree on parity to use // data is split into bytes // sender counts the number of 1s/0s in each byte // each byte is assigned a parity bit to match the parity // receiving device recounts the number of 1s in each byte // and compares to parity used, AND if it doesn't match, an error is reported
133
how check digit can be used
data is input with check digit // calculation is performed on the data // calculated digit is compared to a stored value // if it matches, the data entered is correct // if it does not match, the data entered is correct
134
TLS protocol
− Client/browser requests secure connection to server
− Client/browser requests the server to identify itself
− Server provides a digital certificate
− Client/browser validates the certificate
− Client/browser send signal back to server (to begin transmission)
− Session caching can be used
− A session key is generated
− Encryption method is agreed // data is encrypted
135
two layers of TLS
handshake, record
136
Difference between compiler and interpreter
− An interpreter translates and executes the code line by line
− … whereas a compiler translates and executes the whole code all in one go
− An interpreter stops translating and reports an error as it finds one
− … whereas a compiler produces an error report at the end of translation
− An interpreter does not produce an executable file
− … but a compiler does produce an executable file
− An interpreter will execute the code until it finds an error
− … whereas a compiler will not execute any code if there are errors present
− An interpreter allows correction of errors in real-time
− … whereas a compiler needs to retranslate the code each time after errors are found and corrected
137
when an interrupt signal could be generated
− A peripheral is connected/disconnected
− A key on a keyboard is pressed
− A mouse button click
− A phone/video call is received
− A buffer requires more data
− A printer has a paper jam
− A printer runs out of paper
− A printer runs out of ink
− When switching from one application to another
138
what would happen if interrupt signals were not used in computer
− The computer would only start a new task when it had finished processing the current task // by example
− Computer will not be able to multitask
− Errors may not be dealt with
− Computer would become impossible to use
139
role of an interrupt in generating a message on the comp that the paper has jammed
− Printer generates interrupt
− Interrupt is given a priority
− Interrupt is queued
− Interrupt stops CPU from processing current task
− CPU will service interrupt // Interrupt handler services interrupt …
− … generating an output message to state there is a paper jam
139
why lossless .> lossy
maintains quality // original file is retained, data not permanently lost // significant reduction in file size not required
139
why would you write a software in assembly language
can directly access the hardware // can use special machine-dependent instructions // no need for program to be portable // smaller file size // more efficient use of memory // programs will be more time efficient when running
139
drawbacks of using assembly language
programs are not portable // complex to learn // difficult to debug
139
hoow secure connection is created
* Web browser sends request to web server
* … to view the digital certificate
* Web server sends the digital certificate to the web browser
* Web browser checks the certificate for authenticity
* If certificate is authentic a secure connection is created
* Any data sent is encrypted
* If certificate is not authentic the connection is rejected
* Uses a protocol such as SSL/TLS
140
preventing accidental data loss
create a back-up // data can be restored
add verification // get the user to confirm they want to delete the data
set access rights // she cannot delete any files
141
how the interrupt signal is processed
__ generates interrupt // interrupt given priority // interrupt signal sent to the CPU // interrupt is placed in a queue // CPU stops the task it is currently processing, to check the queue // to service the interrupt // using an interrupt service routine // if __ is highest priority the interrupt is processed // once the interrupt is serviced, a message is displayed to notify the user
142
how analogue sound is recorded and converted to digital
recorded using microphone
sound wave is sampled
measuring the amplitude
each amplitude has a unique binary value
sample rate is et
= number of samples taken per sec
sample resolution is set
= number of bits used for each sample
each sample taken is converted to binary
143
purpose of the operating system
PERFORMS the basic functions of a computer // manages the hardware // provides a platform to run software // provides user interface // performs tasks such as ____
144
why might an error occur when data is transmitted
interference
145
advantages of storing data in cloud storage
data can be accessed from any location
-> can work from anywhere with a connection
Hardware is owned/maintained by a third party
-> aren't responsible for its security
can increase storage needed easily
-> without needing to buy new hardware
cloud system will back up the data
-> does not need to do this cuz it does it for you
146
disadvantages of storing data in cloud storage
INTERNET connection is needed
-> if not available, data cannot be accessed
employees could be pressured to work outside of hours
-> as they can access the data from any location
147
machine learning capabilities
form of artificial intelligence // means it can adapt // can edit its own data // can be trained .// this can be supervised // meanng it can learn with human interaction // analyses patterns and stores SUCCESSFUL results // to influence future decisions // supervised means a user tells the system the input and output
148
differences between primary storage and secondary storage -
P : directly accessible by CPU, S : not directly accessible by CPU
P : stores data currently in use, S : stores USER'S files
P : SOME PARTS are volatile, S : non-volatile
P : SOME PARTS cannot be changed, S : can be changed
P : faster access speeds to data, S : slower access speeds to data
149
similarities and differences between proxy-servers and firewalls
Similarities : check incoming and outgoing signals // store whitelist // block incoming,outgoing signals // both block unauthorised access // keep a log of traffic // both can be hardware or software or both
differences :
P can hid user's IP address, F does not hide
P protects a server, F protects individual computer
P PROCESSES client-side requests whereas firewall FILTERS packets
P transmits website data to the user, F does not
P can hide internal network from internet, F cannot
150
data commonly stored in RAM
currently running data // currently running software //currently running instructions // currently running parts of OS // currently running utility software
151
purpose of secondary storage \
for non-volatile storage of data
to store data that is not currently required by the CPU
to store data to transfer it to another computer
152
what is a pixel
ONE square of ONE colour
153
how does program use AI
use MACHINE LEARNING algorithms
collects data about where it has been
collect data about obstacles
store successful actions
stores unsuccessful actions
identify patterns
to make sure it does not repeat the same incorrect route
so it knows how to react to obstacles next time
154
why biometrics
adds extra level of security // requires properties unique to individual // don't need to remember password
155
similarities between check digit and checksum
both calculate a value from the data // both append the calculated value to the data // both recalculate the value // both report an error if they don't match
156
keylogging
keylogger downloaded without knowledge // keylogger records key presses // data is relayed back to third party // data is analysed // details can then be used to log into account
157
how a browser checks that the website is secure
requests web server to identify itself (request to view the SSL certificate // receives a copy of SSL certificate, sent from the webserver // checks if SSL certificate is authentic // sends signal back to webserver that the certificate is authentic
158
how SSL connection is established
* Browser / client sends request to webserver to request identification
* Web server sends its digital / security certificate
* Browser authenticates certificate
«
*
« if authentic connection, is established
* Any data sent is encrypted
«
*
« using public and private keys
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how image is represented
image made up of pixels
each pixels stores one colour
image has set number of pixels wide by pixels high
each colour has unique binary value
binary value of pixel stored in sequence
160
characteristics of von neuman architecture
both data & instructions sotred in same memory unit
single arithmetic & logic unit
single control unit
uses FDE cycle to execute instructions serially
161
clock speed
max number if FDE cycles a CPU can perform
162
cache
type of storage that stores frequently used data // to speed up access as it;s faster to access than RAM
163
AI
branch of computer science dealing with the simulation of intelligent behaviours by computers
collect data, store rules for using data, ability to learn, by adapting what it does by changing i'ts own rules, by changing its down data, find patterns
