Paper 1 definitions Flashcards
ALU
Arithmetic logic unit: The part of the CPU where data is processed and manipulated. This processing and manipulation normally consists of arithmetic operations or logical comparisons allowing a program to make decisions
Control Unit
The part of the CPU that manages the execution of instructions. The control unit fetches each instruction in sequence and decodes and synchronises it before executing it by sending control signals to other parts of the compter
Register
Tiny areas of extremely fast memory located in the CPU normally designed for a specific purpose, where one piece of data or control information in stored temporarily
PC
Program counter: A register in the control unit which holds the address of the next instruction to be executed
ACC
Accumulator: A special register which holds the data currently being processed by the central processor. Any data to be processed is stored temporarily in the accumulator.
MAR
Memory Address Register: A register in the CPU that stores the address of the memory location currently in use. In the fetch phase, this is the address of the data being used
MDR
Memory Data Register: A register in the CPU that stores data being transferred to and from the immediate access store. It acts as a buffer, allowing the central processor and memory unit to act independently without being affected by minor differences in operation. A data item will be copied to the MDR ready for use at the next clock pulse where it can either be used by the central processor or stored in memory
CIR
Current Instruction Register: A register in in the control unit that stores the address of the next instruction currently being executed and decoded
Buses
A common physical pathway (wire) shared by signals to and from several components of a computer
Data Bus
The part of the bus which carries the actual information
Control Bus
The part of the bus which carries identification about where the data is being sent
Fetch-Decode-Execute
The complete process of retrieving an instruction from store, decoding it and carrying it out
CPU
Central Processing Unit: The main part of the computer consisting of the registers, ALU and control unit
Clock Speed
Measured in Hertz- the frequency at which the internal clock generates pulses. The higher the clock rate, ht faster the computer may work. The clock is the electronic unit that synchronises related components by generating pulses at a constant rate
Cores
A part of a multi-score processor, which is a single component with 2 or more independent actual CPUs which are the units responsible for the FDE cycle
Cache
A part of the main store between the central processor and the rest of the memory. It has extremely fast access, so sections of a program and its associated data are copied their to take advantage of its short fetch cycle
Von Neumann Architecture
Traditional computer architecture that forms the basis of most digital computer systems. A single control unit manages program control flow following a linear sequence of fetch-decode-execute
Embedded systems
A small computer that is part of a wider device or machine, it includes hardware and software and allows users to interact with the machine. eg central heating, washing machines, dishwashers
RAM
Random Access Memory: Volatile main memory with very fast access times. Contains operating system, current instructions and data, and open files or software
Virtual Memory
Part of a disk drive allocated to be used as if it were main memory. It is very slow, and the software will attempt to use the immediate-access store if possible
Volatile
Memory that loses its content when the power is turned off
Non-Volatile
Memory that retains its data when it loses power
Bootstrap Loader
The first program to be loaded into RAM when the device is turned on
POST
Power On Self-Test: determines if all the necessary components are connected and running correctly
Speed
The relative speed that data can be accessed by each type of device
Storage Device
Any medium which holds data or programs
Magnetic Storage
A storage medium which uses surfaces coated with a layer of magnetic material on which data can be stored by magnetically setting the arrangement of the magnetic material. This is done by electromagnetic read/write heads
Flash Storage
A collection of memory chips that is controlled by its own software to make the collection of chips act like a disk drive
Optical Storage
A storage medium that uses plastic discs on which the data is stored as patterns on the surface in pits and lans
Capacity
The amount of data that can be stored on the device, measured in bytes
Robustness
The amount of physical damage that a device can take before it breaks
Cost per Gigabit
A comparison between different storage devices
Platter
A circular disk on which magnetic data is stored. They spin at a high speed so that the reading head can receive the data stored
Sector
A sub division of the magnetic disk, containing a fixed amount of storage space
Track
A circular path on the surface of the disk, where magnetic data is stored
Speed
The relative access speed of each type of device
Portability
The ease with which data is transferred from one location to another whilst being stored on the device
Durability
The ability of the device to withstand knocks and bumps without becoming damaged
Reliability
The approximate lifespan of a device
Pits and falls
The reflective/non-reflective parts of an optical disk that store data
HDD
Hard disk drive, a storage media that stores data as magnetic elements
SSD
Solid state drive- uses flash memory to store data
SD card
Small, portable devices that use flash memory to store data, found in phones, cameras, etc
Data pen/stick
Physically small devices that use flash memory to store data- usually connects to a computer via the USB port
DVD
Digital versatile disk- uses optical methods to store data
CD
Compact disk- uses optical methods to store data
Bit
A single unit of data, usually modelled as 1 or 0
Byte
8 bits of data
Nibble
4 bits of data
Kilo
1000 bits of data
Mega
1,000,000 bits of data
Giga
1,000,000,000 bits of data
Tera
1,000,000,000,000 bits of data
Peta
1,000,000,000,000,000 bits of data
Number base
The positional number system, using unique digits to display quantities, digits are reused and their position displays higher or lower quantities
Denary
Base 10
Binary
Base 2
Hexadecimal
Base 16
Right shift
By shifting a binary number to the right by one column and placing a zero in the least significant column, the number can be doubled
Left shift
The reverse process to a right shift, the number halves
Character set
The collection of symbols, letters and digits that can be represented on a computer
ASCII
American standard for information interchange- a character set
UNICODE
A much larger character set that includes more characters than UNICODE
Pixel
One graphical dot
Metadata
The information at the beginning of a (picture) file, usually the length, height, colour depth and the type of file
Colour depth
The number of colours used in an image (3 bits = 2x2x2 = 8 colours)
Resolution
The number of dots per inch in an image file
Sampling
Sound is gathered at certain intervals (5 times per second)
Sample rate
The rate at which sound is gathered and turned into a digital file
Bit depth
The number of bits available for each sample
Analogue
A value that can take any value between an upper and lower limit
Digital
Values that have to stick to certain numbers
Hertz
The number of cycles per second
Duration
The length of a sound
Compression
Reducing the size of a file
Lossy compression
Reducing the size of a file with permanent data loss
Lossless compression
Reducing the size of a file without losing any data
Dictionary file
Used to store common words/phrases from the compressed file
Run length encoding
A technique used to find repeated data and code it
LAN
Local area network- two or more connected computers in one geographical site using owned infrastructure
WAN
Wide are network- two or more connected computers on more than one geographical site using someone else’s infrastructure
Latency
How long data takes to reach its destination
Error rate
How many transmission errors occur in a set amount of time
Bandwidth
The rate at which data can be transmitted in a network, measured in GB/s
Peer-to-peer network
A type of network in which all workstations are of equal status
Client-server network
A network in which one computer, the server, has overall control
Wireless access point
Sometimes known as a wireless router- sends and receives WiFi transmissions from devices and the network
Router
A device that sends and receives data packets to other routers on different networks, using IP addresses- the device that connects a network to the internet
Switch
Sends data packets to and from their destination on a network using MAC addresses
Hub
Broadcasts data to all other member devices attached to the hub
Transmission media
The physical connection between devices (copper wire, WiFi, fibre optic)
Domain name server
The set of servers that contain all of the URLs and their corresponding IP addresses so that a user can type in the URL and find the target computer with the website on
Hosting
Allowing a website space on a computer which remote users can access the data from
The Cloud
A collection of computers that users can rent space from (usually in a large building called a server farm)
Virtual networks
A sub network inside another. It uses the same infrastructure, but may be reserved for only a few members
Network interface card
A device needed by a device to connect to the network- it provides the device with their MAC address
Ethernet cable
Copper wire
IaaS
Infrastructure as a service- providing hardware resources for rent by users, such as hard drive space
SaaS
Software s a surface- providing applications for users to use online (like OneDrive)
Internet
The collection of devices that are networked together to provide the network of networks
World wide web
The web pages that sit upon the Internet and can be accessed by remote users
IP address
assigned to a device that connects to a network by the network. each one is unique
URL
Universal resource locator- the web address of a webpage
MAC address
Media access control- a unique identifier for the machine connecting to a network. It is built into the hardware and can’t be changed.
Service set identifier
uniquely identifies a wireless LAN
Wired
Devices connected via a copper or optic cable
Wireless
Devices connected via electromagneic signals
WiFi
Uses microwaves to transmit and receive data
Bluetooth
Uses radio waves to transmit and receive data
Encryption
Disguising data so it can’t be read without the key
Standards
Rules set out to allow computers to communicate
TCP / IP
A set of protocols that allow communication on the internet
HTTP
Hypertext transfer protocol- used for transmitting and receiving webpages
HTTPS
Hypertext transfer protocol secure- encrypted transmission of webpages
FTP
File transfer protocol- for transmitting large files between computers
POP
Post office protocol- takes a copy of emails from the webserver and deletes any files on the webserver
IMAP
Internet message access protocol, creates a copy of an email on the web server on the local machine
SMTP
Simple mail transfer protocol- used to send emails
Layers
The use of protocols in layers so that they can be replaced or edited without affecting the other layers
Malware
Software that is hostile or intrusive- it may change, monitor or delete data without the user’s permission
Phishing
A technique used to try and gather personal details from users under false pretences
Social engineering
Using human weakness or gullibility to obtain data
Shoulder surfing
Literally looking over someone’s shoulder as they enter their password
Brute force attacks
Repeatedly guessing someone’s password
Denial of service attacks
the intentional paralysing of a computer network by flooding it with data sent individually from many computers
Data interception and theft
To steal data from a person or organisation
SQL injection
Uses SQL written at the end of a URL to gain access to a remote database
Virus
Software designed to harm the data or computer, which can usually replicate itself
Worm
A form of malware that can replicate itself without being part of another piece of software
Zombies
Can allow someone to remotely use your computer without your knowledge or permission
Keyloggers
Records the keys that have been pressed on a computer and sends them back to the creator, hoping to gain account details or a password
Ransomware
Encrypts the data on a computer and charges a fee to release the encryption key
Trojans
Malware that disguises itself as another type of software, like a music file
Eavesdropping
Intercepting data packets
Network policy
The rules an organisation creates to govern how people will use their system. There is usually an associated Acceptable Use policy
Acceptable use policy
A set of rules that inform users how they are supposed to behave when using the network
Penetration testing
Asking white hat hackers to try and access your network to try and find vulnerabilities
Network forensics
The use of audit trails to find wrong doing on the network
Anti-malware software
Software that looks for malware, it can warn and disable software or files that it identifies as dangerous to the system
Firewalls
A combination of hardware and software that inspect data packets as they leave and enter a computer, designed to prevent unauthorised access to a computer system
User access levels
These determine the rights that a user has to parts of a computer or network
Passwords
A way of restricting access to a system using usernames and the associated code
White hat hackers
Hackers that access a system with permission
Black hat hackers
Hackers that access a system without permission
Grey hat hackers (ethical hacking)
Somewhere in between white hat and black hat hackers that put their expertise into finding vulnerabilities in an organisation’s system without permission, then reports them to the organisation
Black box testing
Asking someone to test the vulnerabilities of an organisation’s system, giving them no more information than any other hacker
White box testing
Asking someone to test the vulnerabilities of an organisation’s system, giving them as much information as an insider would have
Proxy server
Acts as an intermediary between the web browser and the internet, blocking or allowing data packets
Operating system
Manages the general running of the computer and providing a way for the user to interact with the device and providing a platform for applications
User interface
Provides a method for the computer and user to share information
Memory management
The operating system manages the amount of memory that is being used by any running processes
Multi tasking
The ability of the computer to concurrently run several processes at the same time
Peripheral
A device that is plugged into the computer
Drivers
The software that allows the computer to run and interact with a peripheral device
User management
The allocation of usernames, files and permissions for users of the device
File management
The control of the names, structures and permissions that are allowed on files
Buffers
A system of transferring and temporarily storing data
Access rights
The type of access that a user has to data
File structure
The way in which files are linked to each other
Kernel
The computer program at the core of the computer that allows the OS control over all aspects of the computer
Platform
The combination of operating system and hardware that allows computers to run applications
Utility software
Used to analyse, manage, configure and maintain a computer system
Defragmentation
To organise data saved on a hard drive so it is touching
Ethics
The moral code agreed by an organisation
Legislation
The legal framework
Privacy
To keep ones data/activities to oneself
DPA
The Data Protection Act, 1998
Legislation which protects individuals from unreasonable use of their stored personal data
CMA
The Computer Misuse Act, 1990
Legislation which defines electronic vandalism, unauthorised access to computer systems and information theft
CDPA
The Copyright Design and Patents Act, 1988
Legislation which gives creators the right to control the ways in which their material may be used
RIPA
The Regulation of Investigatory Powers Act, 2000
Legislation which regulates the powers of public bodies to carry out surveillance, investigation and interception of communications
Open source
Users can modify and distribute the software
Proprietary
Users cannot modify the software, it is copyright protected and usually paid for
Computational thinking
The thought process involved in formulating a problem and expressing its solution in a way that a human or machine can effectively carry out
Examples of ethical issues
digital divide, invasion of privacy
Examples of legal issues
copyright, hacking, privacy
Examples of cultural issues
censorship, geography of a country
Examples of environmental issues
fossil fuels, lack of natural resources
