GCSE key terms Flashcards
What does the ALU stand for?
Arithmetic Logic Unit
What does the ALU do?
The part of the CPU where data is processed.
This is normally arithmetic operations/logical comparisons so a program can make decisions
what does the CU do?
manages execution of instructions.
Fs, Ds and Es instructions by sending control signals to other components
what is a register?
tiny, fast memory in cpu,
designed for a specific purpose
temporarily stores 1 piece of data/control info
what does the PC do?
Holds the address of the next instruction to be executed
what is the ACC?
register in the ALU
holds data currently being processed.
What does PC stand for?
Program Counter
What does ACC stand for?
Accumulator
What does the MAR contain?
the address of the memory location in use.
in fetch it’s the instruction being loaded
in excecute it’s the address of the data being used
What does the memory data register (MDR) do?
holds the data/instruction ready for transfer to or from memory
What is the CIR?
A register in the CU that stores the address of the instruction currently being executed and decoded
What does MAR stand for?
Memory Address Register
What does MDR stand for?
Memory Data Register
What does CIR stand for?
Current Instruction Register
What is a bus?
A common physical pathway, a wire, shared by signals to and from several components of a computer
What is a data bus?
The part of a bus that carries data
What is an address bus?
The part of a bus that
carries identification about where the data’s being sent
What is a control bus?
A bus that carries command and control signals to and from every component of a computer
What is the Fetch-Decode-Execute cycle?
The complete process of recieving an instruction from store, decoding it and carrying it out
What is the instruction cycle?
Another name for the FDE cycle
What is the CPU?
the main part of a computer: contains registers, ALU+CU
What is clock speed?
the frequency at which the internal clock generates pulse. higher clock speed, faster computer.
the clock is the component that synchronises other components by generating regular pulses
What is clock speed measured in?
Hertz
What are cores?
A part of a multi-core processor (single components with at least independant CPUs)
What is Von Neumann architecture?
Traditional computer architecture where one CU manages program control flow following a linear sequence of FDE
what are embedded systems?
A small computer-hard and software- part of a larger device
allows users to interact w/ the device
Give some examples of embedded systems
Central heating systems, dishwashers, washing machines, engine management systems in cars
What is RAM?
fast, volatile main memory.
When used as main memory, RAM typically can be thought of as containing the OS, programs in use, and data used by those programs
What does RAM stand for?
Random Access Memory
What are the contents of RAM?
The OS
current instructions / data
any open files / software
What is ROM?
Memory where the contents can be read but not changed.
Software is fixed during manufacturing.
Typically holds system boot up instructions.
Can ROM be written to?
No, but more modern versions- *(PROM, EPROM and EAROM) *can
What does ROM stand for?
Read Only Memory
What is stored in the ROM?
POST and BIOS (power on self test and basic input output system)
What is virtual memory?
where part of secondary storage is allocated to be used as if it were main memory when RAM is full.
very slow, so the software will attempt to use RAM if possible
What is Flash Memory?
A type of very fast-access non-volatile memory
What does POST stand for, and what does it do?
Power On Self Test- detirmines if all components are connected and running correctly
What does BIOS stand for?
Basic Input and Output System
What does volatile mean?
Memory that loses its contents when the computer is turned off
What is a bootstrap loader?
first program loaded to RAM when the device turns on
What does speed refer to? (storage)
The relative speed at which data can be accessed by each type of device
What is magnetic storage?
Uses surfaces coated with a layer of mag material
data stored by setting arrangement of the mag. material.
with electromag r/wr heads
What is flash storage?
A collection of memory chips controlled by their own software to make the chips act like a hard drive
What is optical storage?
Storage medium using plastic discs to store data in pits + lans
What is a lan? (not LAN)
A “bump” in optical storage, as opposed to a pit. also called a fall
What is capacity?
The amount of data a device can store
What is capacity measured in?
Bytes
What is robustness?
The amount of physical damage a device can take before it breaks
How do you measure how expensieve a storage device is?
In cost per gigabit
What do you call the way to compare how much physical damage a device can take?
robustness
What is a sector?
A subdivision of the magnetic disk
What is a platter?
A circular disk on which magnetic data is stored. They spin quickly so the read head can recieve the data
What is a track?
a circular path on the surface of the disk where data is stored
what is speed(referring to different storage devices)
the relative access speed of each device
What are the different ways of measuring the effectiveness of different storage devices?
Capacity, durability, robustenss, speed, cost per gigabit, portability
What does HDD stand for?
Hard Disk Drive (magnetic)
What does SSD stand for?
Solid State Drive , uses flash memory
What is an SD card?
Small, portable devices that use flash memory to store data, used in phones, cameras, etc
What is a data pen/stick?
A small device that uses flash memory to store data
What type of memory do data sticks use?
flash memory
What does DVD stand for?
Digital Versatile Disk
What type of storage is a DVD?
optical
What does CD stand for?
Compact Disk
What type of storage do CDs use?
optical
what type of storage do blu-rays use?
optical
what is a bit?
a single unit of data; a 1 or a 0
what is a byte?
8 bits of data
what is a nibble?
4 bits of data, or half a byte
how many bytes are there in a kilobyte?
1,000 or 10 ^3
how many bytes are there in a terabyte?
1,000,000,000,000 or 10^12
how many bytes are there in a gigabyte?
1,000,000,000 or 10^9
how many bytes are there in a petabyte?
1,000,000,000,000,000 or 10^15
how many bytes are there in a megabyte?
1,000,000 or 10^6
what is the order of the standard form prefixes, going up in 10^3s?
kilo,mega,giga,tera,peta
what is a number base?
the positional number system
using unique digits to display quantities,
digits are resused and their position represents higher or lower values
what is denary?
base 10
what is binary?
base 2- 0 and 1
what is hexadecimal?
base 16, uses denary and A,B,C,D,E to represent 10-15
what is a left shift?
By shifting a binary number to the left and placing a zero in the least significant column. this doubles the number (as a left shift in denary would multiply the number by 10)
what is a right shift?
the reverse process of a left shift, divides the number by 2
what is a character set?
the collection of letters, symbols and digits that a computer can represent
what does ASCII stand for?
American Standard for Information Interchange
How many bits does ASCII use?
7/8 (uses 7, stored as 8)
What is an uppercase A in ASCII?
65
What is a lowercase a in ASCII?
97
What does pixel stand for?
Picture Element
What is metadata?
the information at the beginning of a file, usually the length and height, colour depth, type of file, etc
what is colour depth?
the number of colours used in an image
(3 bit = 2^3 = 8 colours)
how many colours would you get in 6 bit colour depth?
2^6 or 64 colours
What is resolution?
the number of dots per inch used in the image file
what is sampling rate?
how many times the computer records the amplitude of the sound per second, eg X times per second
what is sampling?
a computer records the amplitude of a sound at certain intervals and stored as binary
(Frequency is taken from the amplitude)
What is bit depth?
The number of bits avaible for each sample (again, 3 bit = 2x2x2 =2^3 = 8 values)
what does analogue mean?
a value that can take any value between an upper and lower limit
what does digital mean? (referring to storage)
Values that have to stick to certain numbers
what does compression mean?
reducing file size
what does lossy mean?
reducing the file size with permenant loss of data
what does lossless mean?
reducing a file size without losing any data
what is a dictionary file?
used to store common words/phrases from the compressed file (eg the “i have a dream” example mr white showed us)
what is run length?
a technique used to find repeated data and code it
what is a LAN?
A Local Area Network- two or more connected computers in one geographical site, using owned infrastructure
what is a WAN?
A Wide Area Network- two or more connected computers, on more than one geographical site and using someone else’s infrastructure, eg phone lines
what is latency?
how long data takes to reach its destination
what is error rate?
how many transmission errors occur in a set amount of time
what is bandwidth?
the rate at which data can be trasnmitted in a network, measured in Gigabytes per second
what does peer-to-peer mean?
a network where all devices have equal status
what does client-server mean?
a type of network in which one computer, the server, has overall control
what do “peer to peer” and “client-server” refer to?
networks
What is a wireless access point?
Also called a wireless router,
sends/recieves WiFi transmissions from devices & the network
what is a router?
connects a network to the interne
by sending/receving data packets
to/from other routers on other networks
using IP addresses.
What is a switch?
device that sends data packets to/from their destination on a network using MAC addresses
What is a hub?
Broadcasts data to all other devices connected to the hub
What is a domain name server?
servers containing all URLs and corresponding IPs
users type URLs to find the target computer w/ the website
What is transmission media?
the physical connection between devices- copper wire, wifi, fibre optic
what does wifi stand for?
Wireless Fidelity
what does DNS stand for?
Domain Name Server
what is hosting?
allowing a website space on a computer and remote users to access that data
what is the Cloud?
a collection of computers you can rent space on, usually in a server farm
what is a virtual network?
a sub-network using the same infrastructure but reserved for a few members
What is a network interface card?
A device that provides a device with a MAC address so it can connect to a network
What is an ethernet cable?
copper wire, also called a twisted pair
What does IaaS stand for?
Infrastructure as a Service
What does SaaS stand for?
Software as a Service
What is infrastructure as a service?
providing hardware resources for rent
eg HDD space
what is software as a service?
providing applications for users to use online, eg onedrive
what is the internet?
A collection of devices networked together to provide the network of networks
what does WWW stand for?
World Wide Web
what is the world wide web?
the web pages that sit upon the internet and can be accessed by remote users
What is an IP address?
the address that identifies a computer on a network
if the network is the internet, the address is unique in the world.
if the network is behind a router, it is unique in that network
what does URL stand for?
Universal Resource Locator
What is a url?
the web address of a webpage, eg ecosia.org
What is an MAC address?
a unique identifier for a machine connecting to a network
built into the hardware and can’t be changed.
each manufacturer is assigned a group of MAC addresses to be used for their devices.
they come in the form of 1A:7C:2F:3A:9B:12
what does MAC stand for?
media access control
what does SID stand for?
Service Set Identifier
what is an SID?
uniquely identifies a wireless LAN- usually you need a password to connect to WiFi
what does wired mean?
devices connected with copper/optic cables
what does wireless mean?
devices connected via electromagnetic signals
what type of waves does wifi use?
microwaves
how does bluetooth work and what type of wave does it use?
transmits/recieves data using radiowaves
What is encryption?
disguising data so it can only be read with the key
what is an IP address?
a number assigned to a device by a network so it can connected to a network
each IP address on a network is unique, and computers can have different IP addresses on different networks
what are standards?
rules set out so computers can communicate
what does IP stand for?
Internet Protocol Address
What is TCP/IP?
a set of protocols that allow for communication on the internet
what is https?
encrypted transmission of webpages
(hypertext transfer protocol secure)
what is http?
hypertext transfer protocol- used for transmitting and recieving webpages
what is FTP?
file transfer protocol- for transmitting large files across computers
what is POP?
post office protocol- takes a copy of emails from the webserver and deletes any files on the webserver
what is IMAP?
creates a copy of emails on the webserver on the local machine
(internet message access protocol)
what is SMTP?
simple mail transfer protocol-
used to send emails
What are layers?
Using protocols in layers so they can be replaced/edited without affecting other layers
what is malware?
hostile or intrusive software that may change, monitor or delete data without permission
what is phishing?
a technique used to try and gather personal details under false pretences,
a form of social engineering
What is social engineering?
using hmuan weakness or gullibility to obtain data
what is shoulder surfing?
(literally) looking over someone’s shoulder as they read their password
what are brute force attacks?
trying every possible combination to work out a password
what is a DDOS attack?
Intentionally paralysing a network by flooding it with many individual users’ data
what is data interception?
stealing data from an organisation
what is an SQL injection?
uses structured query language, *written at the end of a URL, *to change the state of a database
what is a virus?
software designed to harm data or a computer, can usually replicate itself
what is a worm?
malware that can replicate without being part of another piece of software
what is a zombie?
software that allows someone to remotely use a computer without permission
what do keyloggers do?
record the keys pressed on a computer and send them back to the owner to try and learn a password/account details
what is ransomware?
encrypts the data on a computer and charges a fee for the key
what is a trojan?
malware that disguises itself as another type of software, for instance a musical file
what is eavesdropping?
intercepting data packets
what is a network policy?
rules an organisation creates to govern how people use their system, usually there is an Acceptable Use Policy
What is network forensics?
using audit trails to find wrongdoing on a network
What is penetration testing?
Asking white hat hackers to try access your network “without” permission to try to find vulnerabilities
what is anti-malware software?
software that looks for malware
can warn about/disable
software/files identified as dangerous
what is a password?
a way of restricting access to a system with usernames and an associated code
what are firewalls?
combination of soft and hardware that inspect packets as they leave/enter to prevent unauthorised access
what are user access levels do?
determine the rights a user has on a computer/network,
usually:read only, r/wr, full and administrative access
what is encryption?
a method of disguising data so it can only be read with the key
what are white hat hackers?
Hackers that access a system with permission to help with it security
What are black hat hackers?
hackers that access systems without permission
what are grey hat hackers?
Hackers who find vulnerabilities in an organisation’s system without permission to report to them
What is black box testing?
asking someone to test a system’s vulnerabilities knowing no more info than a hacker would
What is white box testing?
To ask someone to test a system’s vulnerabilities, giving themthe information an insider might have
what is ethical hacking?
Hackers put their expertise into finding vulnerabilities in an organisation’s system without permission to report it to the organisation
what are audit trails?
A log of activity on a network
what is a proxy server?
acts as an intermediatry between web browser and internet, blocking or allowing data packets
what does an OS do?
manages the general running of a computer,
so a user can interact w/ it
what is a user interface?
provides a method for the computer & user to share information
what is memory management?
the OS manages how much memory is being used by any running process
what is multitasking?
a computer’s ability to run several processes simultanesouly or to simulate concurrent processing
what is a peripheral?
a device that is plugged into a computer, eg printer
what are drivers?
software that allows computers to run and interact with a peripheral device
what is user management?
the allocation of usernames, files and permissions for the user
what is file management?
the control of
names,
structure
and permissions
allowed on files
what is a buffer?
a system of transferring & temporarily storing data
when fast and slow devices communicate
what are access rights?
the type of access that a user has to data, usually read only, read and write or full control
what is file structure?
the way in which files are linked to each other?
what is a kernel?
the program at the core of the computer
allows the OS full control
what is a platform?
the combination of OS and hardware that allows the computer to run apps
what is utility software?
used to analyse, manage, configure and maintain a computer system
what is encryption software?
software that encrypts data so it can only be read with the key
What does defragmentation software do?
organises data on an HDD so it’s contiguous
what is compression?
reducing file size
What are ethics?
the moral code agreed by an organisation
what is legislation?
the legal framework
what is privacy?
keeping one’s data / actions to oneself
what is the data protection act/DPA?
protects people from unreasonable use of their personal data
When was the DPA?
1998
What are the three levels of the CMA?
-Access without permission
-access without permission with intent to change
-access and change without permission
What is the CMA?
defines electronic vandalism,
unathorised access to computer systems
&information theft
What is the CDPA?
Legislation to give creators the right to control how their artistic works are used
What does CDPA stand for?
Copyright Design and Patents Act
What does RIPA stand for?
The Regulation of Investigatory Powers Acts
When was the CMA?
1990
When was the CDPA?
1988
When was the RIPA?
2000
What is the RIPA?
Legislation to regulate the powers of public bodies to carry out surveillance/investigation
covers interception of communications
give some examples of ethical issues surrounding computing
losing jobs to automation
unequal IT access (digital divide)
invasion of privacy
irresponsible internet content
give some examples of legal issues surrounding computing
digital content ownership and copyright
different laws in different countries
(crime may be comitted in a certain country but the people may be physically living in another country) hacking
piracy
give some examples of environmental issues surrounding computing
manufacturers use fossil fuels,
non-renewable resources eg gold,
data centers use 2% of global energy,
computers contain hazardous materials which are shipped to other countries for disposal
give some examples of cultural issues surrounding computing
censorship to provide political unrest and preserve culture,
a country’s geography/economy affects access network/power access
increased mobile technology impacts communication,
cyberbullying
what does open source mean?
Software that users can modify/distribute
support provided by the community.
users have access to source code
may not be fully tested
what does proprietary mean?
users can’t modify the software
copyright protected, usually paid for
licensed per user/computer
users can’t access source code
fully tested&supported by devs
what is computational thinking?
the thought processes involved in formulating a problem and expressing its solutions in a way that a computer- human or machine- can carry them out
what word do you use when describing whether files are next to each other (related to defragmentation)
contiguous
what are the words for encrypted/non encrypted text
cipher/plain text
What is the first network layer?
passes data as electrical signals over the physical network
What is the second network layer?
Involves making connections between networks and directing data
What is the third network layer?
Involves splitting data into packets and checking data is sent (tcp is an example of this)
What is the fourth network layer?
turns data into apps / websites and vice-versa
What is Transmission Control Protocol?
Sets rules for how devices connect on the network.
Splits data into packets+reassembles them.
Checks data is sent+delivered
