Hardware and Communication Flashcards
Active System
have a small battery within the tag, and the device will transmit its identifier at regular intervals. Depending on the power supply, the range can be up to 200 metres. Commonly used in security tags in shops
Alt Text
appears on the screen as an ‘alternative’ if the image can’t be displayed, but it is also an accessibility feature as it is the text that is used by a screen reader
Amdahl’s Law
T(n)=T(1)(B+(1/n)(1-B))
estimated runtime in a multi-core processor
ADC
Analogue to Data Converter
creates digital sound signal in microphones
ALU
Arithmetic Logic Unit
performs all the mathematical calculations and logical operations in the CPU, used to perform calculations, make logical decisions and returns the answers to the accumulator
Arithmetic Pipeline
divides up an arithmetic operation into its individual steps and each step is performed overlapping the next step
Bandwidth
determines the amount of information the processor can process in a single instruction, measured in bits
Barcode
an extra digit or character added to the end of a long code, computed by applying an algorithm to the other digits. When the long code is entered, the check digit is calculated and compared to the check digit at the end of the code and if it doesn’t match, it isn’t validated
Bayer Filter
used in digital cameras to determine the colour of each pixel, this sits above the image sensor and provides an array of red, green, and blue filters, one for each photosite. There are twice as many green filters, as this matches the colour sensitivity of the human eye.
Benchmark Testing
involves measuring the performance and capacity of the CPU when doing tasks such as 3D rendering, floating point maths tests and file compression which take up a significant amount of memory
Biometrics
physical characteristics such as fingerprints, facial images, irises and voice
Biometric Spoofing
a term used to describe a method of fooling biometric scanners
Buffer
area of memory used in transfer of data between devices; each hardware device is assigned a buffer during system start-up
Bus
something that connects processors to another part of the computer
Address Bus
where the address of the data is communicated to main memory. The width (number of wires) defines the amount of physical memory that can be addressed
Control Bus
used to tell the memory or the device the operation is to be performed
Data Bus
a series of wires that connects the processor to the main memory (RAM) or cache memory. Can be used to read from or write to memory
FSB
Front Side Bus
the interface between CPU and memory, can only go as fast as clock speed, determines how quickly data can be sent from the CPU to the rest of the system
Byte Accessible
when locations can hold a byte of data instead of a bit
Cache Controller
a chip that manages retrieval, storage and delivery of data to and from cache memory or a hard disc
Cache Memory
very fast storage memory built into the CPU that is used to speed up the processing of instructions, holds frequently used instructions and data and is searched before the CPU searches main memory
L1 Cache
physically part of the CPU and is the smallest and fastest cache
L2 Cache
close to the CPU and main memory, is slightly larger and slower than L1 and is searched after the L1 cache
L3 Cache
in parallel archictecture, this can be accessed by all cores, is the largest and slowest core, instructions are searched for in here after searching the two cores, is still faster than the RAM
Central Processing Unit (CPU)
main processor that executes information in a computer
Chain
a series of clusters that make up a file, which can be scattered all over the hard disc
CISC Processor
Complex Instruction Set Computer Processor
includes a complete set of special purpose circuits that carry out variable sized instructions at very high speeds, reducing program size and the required number of memory cycles to execute the program
Clock
refers to a pulse or signal used to synchronise processes occurring within a computer, has a constant tick that switches between 1 and 0
Clock Speed
measured in either megahertz or gigahertz, depends on the number of ticks per second
Cluster (Disc)
group of sectors that are arranged next to each other on the same segments
Cluster (Servers)
where redundant servers use spare servers to take over if they go down
Computer
a machine that can be programmed to manipulate symbols, which responds to a specific set of instructions in a well-defined manner, executes a pre-recorded set of instructions and quickly stores and retrieves large amounts of data
Contemporary Processor Architecture
modern architecture concerning computer processing
Array Processing
where a processor performs computations on a vast array of data, only executing one instruction at a time on an array of data to enhance the computer’s performance
CPU Cache
a small, fast memory store located within the CPU which is searched before anywhere else and holds copies of the most frequently used data
Co-Processor
an additional processor used in some computer systems to perform specific tasks, generally mathematical ones that generally take up a lot of memory
GPU
Graphics Processing Unit
used to rapidly render detailed graphics
Maths Co-Processing
used to rapidly carry out floating point maths operations
Parallel Processing
takes place in computer systems with multiple cores, where each core executes instructions simultaneously. In theory, this would double the computer’s performance, however, this does not actually happen because some memory is used in allocating instructions to cores and sometimes instructions can’t be executed simultaneously because other instructions need to be executed first
Pipeline Execution
involves simultaneous execution of more than one instruction to increase performance, where multiple instructions are overlapped during execution
Control Unit
directs the flow of instructions and/or data/coordinates the other parts of the CPU/generates clock ticks or controls the clock: includes two main parts: the clock, and the decoder
Cores
a complete CPU in its own right which can carry out any instructions
Delta Change Backup
only data changed since the previous back up is backed up, but the previous copy is also maintained in case it needs to be restored, useful as it is faster than completing a full backup
Demosaicing Algorithm
an algorithm in a digital camera that converts the analogue signal into binary form, so that each pixel is represented by a numerical value
DAC
Digital to Analogue Converter
a system that converts digital signal into analogue signal
Directory Table
stores the details of every file within that directory, which include the starting cluster of the file, the file name, the file extension, file attribute, date of creation and file size
Disc Defragmentation
where utilities juggle the contents of memory sectors around to keep files together as much as possible, making the computer run quickly and efficiently
Disc Fragmentation
where a file has been broken up across too many separate memory sectors, slowing down the access times of the file
Disc Thrashing
where the hard drive is being used for virtual memory because the RAM is full, giving the illusion of larger RAM
EEPROM
Electronically Erasable Programmable Read-Only Memory
non-volatile RAM
FAT
File Allocation Table
this keeps a record of every cluster on the hard disk and each record points to another record so a chain can be traversed
Flip-Flops
a type of circuit with two states, on and off, used to store data in solid state
Generation File Backup
involves storage of the three most recent versions of the master file, useful if one version is corrupted because the previous ones are still available but data should be stored off site in case of a disaster
Son Version
the most recent backup of the master file
Father Version
the second most recent backup of the master file
Grandfather Version
the third most recent backup of the master file
Hard Disc
stores all digital content eg documents, pictures, music, videos, programs, application preferences, and operating system representing digital content stored on a hard drive
Harvard Architecture
similar to the Von Neumann model, except that it has two distinct sets of address and data buses, one of which is used for reading data from and writing data to the memory and the other is used for fetching instructions, solving the problem of the Von Neumann bottleneck
Hybrid Drive
have both magnetic and solid state drives, giving the benefits of both
Incremental Backup
only backs up data that has changed and writes over older backups, useful as it saves storage space and is faster than full backup, but only allows the user to restore the most recent backup
Input Device
allows data to be inputted into a computer system
Biometric Device
software that uses biometric data such as fingerprints or irises
Braille Keyboard
a type of keyboard specifically designed for people who read Braille, with Braille characters on the keys instead of normal letters
Concept Keyboard
a keyboard with specific buttons instead of letters and numbers, often used in assistive and augmentative communication
Data Gloves
a wired glove used for inputting information, used to capture physical data such as the bending of the fingers
Digital Camera
used to capture images, these work by opening a shutter to allow light into the camera, focusing the light on an image sensor, which breaks the picture up into millions of pixels
Eye-Tracking Device
a form of assistive technology that is controlled by the eyes
Fingerprint Scanner
often used to access phones and computers and to authorise small payments, but are easily spoofed as fingerprints can be damaged by cuts and it is easy to acquire copies
Foot Switch
a form of assistive technology that allows the user to control input to a system through a series of pedals
Flatbed Scanner
allows users to scan a physical document such as a photograph, handwritten note, or important letter and save it as a digital bitmap image
Game Controller
a device used with video games or entertainment systems to provide input to a video game, typically to control an object or character in the game
Graphics Tablet
also known as a drawing tablet, this is used to create digital drawings with a special Stylus by pressing the tip on the tablet surface
Iris Scanner
an increasingly major part of security systems and one of the most secure forms of authentication, as the iris is protected by the cornea
Keyboard
allows a user to enter character data (numbers, letters, and symbols). It often has function keys or special purpose keys to perform common user tasks such as sending signals to control the volume or to switch between windows
Laser Scanner
used to scan barcodes and QR codes, can be small wired or wireless handheld devices, or larger fixed units, and some have multiple lasers to make them easier to use
Light Pens
a handheld photosensitive device resembling a pen used to pass information to a computer
Magnetic Stripe Card Reader
capable of reading the data on things such as hotel door access cards contain a magnetic strip that holds data
MICR
Magnetic Ink Recognition
uses a combination of ink containing iron oxide and specific fonts so that data written using this ink can be read by an MICR. Only MICR ink can be picked up, everything else will be ignored, even stuff written over the top of the MICR ink. This is used almost exclusively for cheques
Microphone
captures analogue sound waves and converts them into electronic signals
Mouse
allows a user to ‘point and click’ to select icons, or to position the cursor on the screen
NFC Reader
Near Field Communication Reader
reads data from an NFC tag, uses radio waves to read data from a bank card or mobile phone when the two devices are close to each other, allowing contactless payment
OMR Scanner
Optical Mark Recognition Scanner
often used to input the answers or marks that a candidate has made on a multiple choice test paper; work by focusing a beam of light onto the answers, because the white paper reflects back the light and the black ink doesn’t reflect it back as well
QR Code Scanner
Quick Response Code Scanner
these do not use lasers; the codes are captured and read by taking an image of the QR code, either with a dedicated scanner, or by using a camera and app on a mobile device
Radio Frequency Identification Tags
allows data to be transmitted wirelessly over radio waves. There are two parts to an RFID system: a tag and a reader. Use of radio signals means that the system does not require a line of sight between the tag and the reader. RFID tags are made up of an antenna, for receiving and transmitting the radio frequency signals, and a chip, which processes the signals. Each tag has a unique identifier and will often store some additional data in a non-volatile memory cell.
Sensor
a device which detects or measures a physical property and records, indicates, or otherwise responds to it
Accelerometer
an instrument for measuring the acceleration of a moving or vibrating body
Ambient Light Sensor
a photodetector that is used to appropriately dim or brighten the device’s screen
Barometer
an instrument used to measure atmospheric pressure, used in forecasting the weather and determining altitude
CCD
Charge-Coupled Device
a light-sensitive integrated circuit that captures images by converting photons to electrons and breaks the image elements into pixels
CMOS
GPS Reciever
Global Positioning System Receiver
processes the signals broadcasted by GPS satellites
Gyroscope
a device consisting of a wheel or disc mounted so that it can spin rapidly about an axis which is itself free to alter in direction. The orientation of the axis is not affected by tilting of the mounting, so gyroscopes can be used to provide stability or maintain a reference direction in navigation systems, automatic pilots, and stabilizers
Image Sensor
an array of millions of photosites, which are light-sensitive elements that measure the intensity of light, therefore breaking the image up into millions of pixels
Magnetometer
an instrument used for measuring magnetic forces, especially the earth’s magnetism
Thermometer Proximity Sensor
a sensor able to detect the presence of nearby objects without any physical contact
Sip and Puff Device
a pneumatic piece of assistive technology that allows the user to control computer systems by drawing or blowing air into a sensor reader, which can be used to switch things on and off, or control a wheelchair or keyboard
Smart Card Reader
often found in retail shops, reads data taken from the integrated circuit chip found on a customers bank card to enable a transaction to take place
Touchscreen
designed to both input and output data, allows the user to use their finger or a stylus to select icons, use an on-screen keyboard, and perform navigation tasks
Capacative Touchscreen
much cheaper and are made of two thin transparent sheets, when these touch each other, a voltage is recorded at that position. A certain amount of pressure is needed to make the sheets touch. This does not provide as sharp an image as capacitive screens, nor do they allow for multiple touches
Resistive Touchscreen
much cheaper and are made of two thin transparent sheets, when these touch each other, a voltage is recorded at that position. A certain amount of pressure is needed to make the sheets touch. This does not provide as sharp an image as capacitive screens, nor do they allow for multiple touches
Trackpad
offers the same functionality as a mouse but the user controls the movement of the cursor using their fingers. It is commonly found on laptop computers
Voice Recognition Software
a form of biometric software that can recognise the unique characteristics in someone’s voice, such as vocal tract, pitch and accent
Vocabulary Dictation
can be used to input data into a computer system, where a user will speak into a microphone and the computer will try to change the spoken words into typed text. Vocabulary dictation is a popular interface as it is natural for people to communicate in this way. Specialist vocabularies are available with additional words for particular types of users, such as medical and financial users
Voice Input
can be used to issue spoken commands to a computer system via a microphone, and the computer will try to interpret the commands and carry them out. This is different to vocabulary dictation as there is a set amount of commands tat the computer is able to carry out
Voiceprint Recognition
the process of capturing a person’s voiceprint then digitising and storing this data on a computer system. This is often used in security systems, where a person may attempt to gain entry to a high security room. When entry is attempted, the voiceprint of that person is again captured. These two data items are compared, with entry being allowed if there is a match
Webcam
a video camera that is connected to a computer or integrated in a device and allows its images to be seen online
Instruction Pipeline
will pre-fetch the next instruction and data and store it in a register. As one instruction leaves the current instruction register (CIR), the next one is ready to be loaded and decoded. At any given point, there are instructions being fetched, decoded and executed.
Inter-Process Communications
where different threads within parallel processing are able to communicate with each other, requires specially written programs
Interrupt
a signal to the CPU indicating that CPU time is required to deal with some event, can be generated by hardware, software and users
Kernal
a part of the computer’s operating system that generally has complete control over everything in the system
Latency
average amount of time taken for the other end of that link to respond
Mass Storage Device
allows a computer to permanently retain large amounts of data and program between jobs, includes disc drives and tape drives
Memory
allows a computer to store, at least temporarily, data, programs and immediate results
Middleware
software that acts as a bridge between an operating system or database and applications, especially on a network
Millennium Bug
a problem with some computers arising from an inability of the software to deal correctly with dates of 1 January 2000 or later
Multi-Core Processor
an integrated circuit that has two or more processing cores, meaning it can theoretically carry out more than one instruction at once
Output Device
allows data to be extracted from a computer system
3D Printer
allows for three-dimensional designs on a computer to be printed in solid form
Digital Screen
a form of display on either a stand-alone monitor or built-in screen
Headphones
a pair of small loudspeaker devices worn on the ears for listening to audio signals
Inkjet Printer
use liquid ink to produce black-and-white or colour prints, can often handle specialist paper and print at very high resolutions (with the ability to show a large amount of detail)
Laser Printer
a type of printer that uses powdered ink called toner, that do not produce as high a quality of prints as inkjet printers
LCD Screen
Liquid Crystal Display Screen
the most common display found in offices and on standard desktop and laptop computers, but are increasingly being phased out in favour of LEDs
LED Screen
Light Emitting Diode Screen
a cheaper and more environmentally-friendly alternative to the LCD
OLED Screen
Organic Light Emitting Diode Screen
a lighter and more flexible variant of the LED for mobile phone screens
Plotter
a device that uses one or more pens to draw an image, commonplace in architectural and engineering practices
Refreshable Braille Display
a form of assistive technology that displays characters as a series of dots formed by pins that protrude through the flat surface of the device, allowing people to access webpages or e-books by reading Braille
Speakers
a device that generates sound waves from data being received from a sound card, often built into devices but can also be connected as external peripherals
Overclocking
where the CPU’s clock is set to run faster that its original design. Whilst this may seem like a good idea, it can lead to overheating, therefore manufacturers do not endorse overclocking.
Parallel Architecture
CPU with multiple cores
Single-Core Processor
a core with only one processor
Dual-Core Processor
a CPU with two distinct processor simultaneously working in the same integrated circuit, in theory is twice as fast as a single core processor
Quad-Core Processor
a CPU with four distinct processors simultaneously working in the same integrated circuit, in theory is twice as fast as a dual-core processor
Passive Device
do not contain a power supply. Instead, the device is powered by radio energy transmitted by the reader. The antenna collects the energy from the transmitter to activate the chip. The range of a passive system is up to 1 metre, and some systems require the reader to be very close to the tag
Pipeline Flushing
a procedure executed by a CPU when it cannot ensure that it will correctly process its instruction pipeline in the next clock cycle
Platter
the particles of the magnetic disk that are either positively or negatively charged
Processor
provides the instructions and processing power the computer needs to do its work
QR Code
Quick Response Code
typically used to provide a link to a particular page on a website, or to provide a link to an email or app that holds, for example, purchase details for concert tickets or travel information such as train times and seat numbers for a journey, can store 7,089 numbers or 4,296 characters and because of the higher storage capacity, these are increasingly replacing barcodes
RAM
Random Access Memory
the computer’s working memory, is volatile and editable, data is lost when the computer is powered down, allows multi-tasking. When the computer is on, it runs the operating system, all the other programs that are running and any data files that are in use
DRAM
Dynamic Random Access Memory
a cheap form of RAM that holds data very densley
SDRAM
Synchronous Dynamic Random Access Memory
improves performance through its pins, which sync up with data connection between the main memory and the microprocessor
DDR SDRAM
Double Data Rate Synchronous Dynamic Random Access Memory
same as the SDRAM, but with twice the data
ECC DRAM
Error Correcting Code Dynamic Random Access Memory
a type of DRAM that can find corrupted code and even fix it
NVRAM
Non-Volatile Random Access Memory
a type of RAM that does not lose data when the computer is shut down
Printer Memory
RAM built into a printer
SRAM
Static Random Access Memory
uses flip-flops and transistors to be much faster than DRAM, but is also far smaller
Video RAM
Video Random Access Memory
the memory a GPU uses to store the information it needs to render images on a display
RAID
Redundant Array of Independent Discs
used with both SSD and HDD and allows multiple drives to be brought together as a single drive
RAID 0 Striped
this provides improved performance and additional storage, however it does not provide any fault tolerance, so any errors on the discs could destroy the RAID
RAID 1 Mirrored
each disc provides the same information, which provides some fault tolerance; as data is repeated, read speed is increased (because it can be read from any disc), but write speed is decreased (because all discs must be updated).
RAID 3-6 Striped Parity
this requires three discs in the array, providing fault tolerance, parity checks and error correction, other drives can continue when one fails, lost data can be calculated using parity data stored on the separate parity drive, involves sacrificing storage space to increase redundancy
RISC
Reduced Instruction Set Computer Processing
a type of microprocessor that uses a small set of instructions of uniform length, generally executed in one clock cycle, simple to design and inexpensive, but is slow due to the computer having to repeatedly perform simple operations to execute a larger program
Register
a storage location found in the CPU where data or control information is stored temporarily. Usually much faster to access that internal memory
ACC
Accumulator
temporary stage register that has data from the arithmetic logic unit sent to it
CIR
Current Instruction Register
the part of a CPU’s control unit that holds the instruction currently being executed
Internal Memory
the memory that is available within the CPU
Internal Register
these are used by the processor, in conjunction with fetching information from the RAM
User Accessible Register
these are used within programmable instructions
MAR
Memory Address Register
the CPU register that stores the memory address from which the data will be fetched to the CPU
MDR/MBR
Memory Data Register/Memory Buffer Register
used for holding information (either program words or data words) that is in the process of being transferred from the memory to the central processor, or vice versa
PC
Program Counter
a processor register that indicates where a computer is in its program sequence
Status Register
indicates if a calculation has produced an overflow error
Reserved Cluster
a cluster that is not available to store files
Saving
copying data to secondary storage before it is switched off
Secondary Storage
retains its contents when the computer switched off, stores both programs and data, and is used for saving and running programs as internal memory is volatile and data needs to be stored somewhere. There are three types of secondary storage
Magnetic Storage
stores technology in magnetic mediums, in binary data, on a disc or tape that is coated with magnetic material. The magnetic medium is polarised, with North being 1 and South being 0. Examples include hard disc drives. Advantages include speed and the fact that the data can be read directly from any part of the hard disc. Disadvantages include durability and cost
Optical Storage
uses laser technology and stores binary data on a reflective surface. Some areas reflect laser light and some don’t. If the laser is reflected, it represents 1, if not, it represents 0. Examples include CD, DVD and Blu-Ray. Advantages include storage, portability and speed. Disadvantages include durability, memory and the fact that data cannot be overwritten
Optical-R
an optical disc that can be written to once by a home user but not overwritten
Optical-ROM
a read only optical disc
Optical-RW
an optical disc that can be read and written to multiple times over
Solid State Storage/Flash Memory
this is called solid state as it doesn’t have any moving parts and is increasingly replacing magnetic and optical, stores binary data on semi-conductor material and different areas act as switches. If the switch is open, it represents 1, if closed, it represents 0. Examples include solid state drives. Advantages include durability, speed and power consumption. Disadvantages include storage and data cannot be overwritten unless it is deleted first
Self-Modifying Code
code that alters its own instructions while it is executing
Screen Reader
a form of assistive technology that reads the contents of the screen to the user
SD Card
a type of portable solid-state storage that has no moving parts that uses very little power and generates very low amounts of heat, but has a high storage capacity compared with optical discs
Seek Time
average amount of time taken to read/write from a disk unit
Simplex
data can only be sent in one direction; one node sends, the other receives
Solid State Drive
the same as a hard disc, but uses flash memory and is often used in mobile devices
Stored Program Concept
a program must be stored in main memory to be executed and its instructions are fetched one at a time and executed serially
Switch
similar to a hub but only sends data to specific ports, greatly reducing data collisions
Text-to-Screen Utilties
a form of assistive technology that reads the contents of the screen to the user
Throughput
a measure of how many units of information a system can process in a given amount of time
Toner
a type of powdered ink used in laser printers
Trace Table
used to dry-run your program to see how the variables and output changed throughout the program
Transistor
a semiconductor device with three connections, capable of amplification in addition to rectification
Virtual Memory
when the system is running low on RAM, secondary storage is used so it seems like the program is running from RAM. A PC with limited RAM becomes slow if too many programs are running or too many large files are being loaded. Only some blocks of RAM are actively used at any given time, because the Operating system copies inactive data blocks from RAM to the hard disk and copies active data blocks from the hard disk to RAM
Underclocking
where the CPU’s clock is set to run slower than its original design. This can lead to the the computer running very slowly
Von Neumann Architecture
a computer architecture based on a 1945 description by John Von Neumann, with one memory unit and set of buses which is sued to access either data or programs, so is cheaper and simpler to produce, and an error in the program could corrupt all data and instructions
Von Neumann Principle 1
instructions are executed in a linear sequence
Von Neumann Principle 2
data and program instructions are stored together in the same memory and are indistinguishable
Von Neumann Principle 3
the CPU is controlled by a single unit
Von Neumann Bottleneck
the relatively slow speed at which data can be transferred between CPU and memory, compared with the amount of memory, causes the Von Neumann bottleneck. This limits the performance of the computer. To overcome this, we can use a range of techniques including memory caching, separate paths for data and memory and parallel processing
