Vocabulary Flashcards
ASCII -
a character set. Each letter on the keyboard has a unique ASCII value that can be represented in hexadecimal or decimal.
Bit -
Binary Digit. Either 1 or 0, On or Off.
Byte -
Smallest unit or memory. A collection of 8 bits.
Gigabyte (GB) -
1024 megabytes. 2 to the power of 30 bytes.
Kilobyte (KB) -
1024 bytes. 2 to the power of 10 bytes.
Megabyte (MB) -
1024 kilobytes. 2 to the power of 20 bytes.
Memory dump -
output of memory contents onto the printer or screen. Usually represented in hexadecimal.
Petabyte (PB) -
1024 terabytes. 2 to the power of 50 bytes.
Spooling -
Data are temporarily held in a buffer waiting for an output device to access it.
Terabyte (TB) -
1024 gigabytes. 2 to the power of 40 bytes.
Asynchronous data transmission -
Data sent in an agreed bit pattern with control bits. The received knows when the transmission starts and ends.
Checksum -
The sum of all the bytes in a transmission is sent with the data. Used with credit card numbers. Checks whether data has been changed or corrupted following transmission.
CSS –
Cascading Style Sheet. Controls presentation of page. Enable multiple pages or elements on a page to be changed in one go.
Echo Check -
Data is sent to another device and is sent back again to the sender. The two sets of data are compared to spot any errors.
Even Parity -
Used with parity checking and parity bits where each byte of data has an even number of 1 bits in it.
Full duplex data transmission -
data can be sent in both directions at the same time.
Half-duplex data transmission -
data can be sent in both directions but only one at a time. e.g. walkie talkies
HTML –
HyperText Mark-up Language. Used to write and develop webpages to present text. Uses tags.
HTTP -
Hypertext Transfer Protocol. Protocol used by web browsers
HTTPS –
Hypertext Transfer Protocol Secure. A set of rules to be followed when transferring files across the Internet. The S is for secure with private data.
IP address –
a number assigned to each device on the Internet. Assigned by ISP. Gives you the location. MAC address gives you each person in the location.
ISP –
Internet Service Provider. A company you pay to give access to the Internet.
MAC address –
Media Access Control. A number that uniquely identifies a device on the Internet. Often refers to network card. Rarely changed. Usually 12 or 16 hex digits. First 6 or 8 refer to manufacturer code. Last 6 or 8 is the serial number of the device.
Odd parity -
used with parity checking where each byte has a parity bit. Each byte would have an odd number of 1s in it.
Parallel data transmission -
several bits (usually one byte) are sent down several wires at the same time. Risk of skew when bits arrive out of sync.
Parity Check -
A method to check whether data has been changed or corrupted following data transmission. Uses odd or even parity
Serial data transmission -
data is sent one bit at a time over a single wire. Goo d over longer distances.
Simplex data transmission -
data sent in one direction only. e.g. computer to printer.
URL –
web address. Consists of protocol, web server name and file name.
USB -
Universal Serial Bus. An asynchronous serial data transmission method. (Never use USB as a replacement term for memory stick).
Web browser –
software which allows a user to display a web page on their computer screen
Address Bus -
Carries address of the next item to be fetched. Unidirectional.
Architecture -
How a computer system is designed.
ARQ -
Automatic Repeat Request. Checks whether data has been correctly transmitted by sending an acknowledgement that data has been sent correctly. A timeout is the time allowed to pass before an acknowledgement is received. If no acknowledgement is received before the timeout elapses, the message is automatically resent.
Buffer -
A temporary memory area in a device.
Control Bus -
Carries signals relating to the control and co-ordination of all activities within the computer (e.g. read/write functions). Unidirectional or Bidirectional.
Control Unit -
Controls the operation of the memory, processor and input/output devices
CIR (Current Instruction Register) -
Stores the instructions that is currently being executed.
Data Bus -
Carries data that is currently being processed / that will be / that has been processed between the processor, the memory unit and the input/output devices. Bi-directional.
Fetch-Execute Cycle -
A feature of Von Neumann architecture. Data is fetched from the memory address in the PC, stored in CIR, then the PC is incremented. Instruction is then decoded and executed.
Interrupt -
a signal that causes the operating system to take a specified action
MAR (Memory Address Register) -
Contents of the PC are copied to the MAR via the address bus.
MDR (Memory Data Register)
- Contains the contents of the memory location specified in the MAR.
Memory Management -
A process of assigning blocks of memory to programs running in a computer
Memory Unit -
Made up of addresses and contents. Identifies every location in memory and the contents of each location.
Multi-tasking -
Many processes appearing to the user to run simultaneously.
Operating System -
The software running in the background of a computer system. It manages many of the basic functions such as multi-tasking, error handling, memory management, input and output control and human computer interface.
Parity bit -
Set to 1 or 0. Sent with a byte of data to make the total number of 1s odd or even for each byte.
PC (Program Counter) -
Contains the address of the memory location of the next instruction to be fetched.
Register -
High speed storage area within the computer.
Utility -
A program that performs a specific task required for the operation of a computer system.
Von Neumann Architecture -
computer architecture that holds programs and data in memory. Data moves between the memory unit and the processor.
Actuator -
An electro-mechanical device used in control applications with sensors. Examples would be relay, solenoid or a motor.
ADC -
Converts physical values into discrete digital values. Could be used in speech recognition. Analogue Digital Converter.
Additive Manufacturing -
Used by 3D printers to build up an object layer by layer.
Barcode -
Series of dark and light lines of varying thickness representing binary values. No need to price each item and allows automatic stock control. Guard bars separate the left and right hand side of the barcode.
Binder 3D printing -
Two passes for each layer. First sprays dry powder, the second a binder (type of glue) is added to make a solid layer.
Capacitive Screen -
made up of layers of glass that act like a capacitor. Electric fields are created between the layers which changes when touched. Allows multi-touch.
CCFL -
Cold Cathode Fluorescent Lamp. Before LEDs, this method was used for backlighting.
Concept Keyboard -
a flat board with buttons. Each button can be programmed to do whatever you want. Ideal at a fast-food checkout for example.
CT Scanner -
Computed Tomographic Scanner creates a 3D image of a solid object by taking very thin “slices” with X-rays or radio frequencies.
Control System -
a computer system that uses sensors to alter devices according to criteria. E.g. street lighting, traffic control, burglar alarm.
DAC -
Digital to Analogue Converter. Sound can be produced by passing digital through a DAC to an amplifier and then to a speaker.
Direct 3D printing -
works like an inkjet printer. The print head moves left and right and also up and down to build up the layers of an object.
DLP -
Digital Light Projector. Contains millions of micro-mirrors on the DLP chip. When tilted towards the light source they are on. When tilted away, they are off.
Infra-Red Screen -
Uses glass as the screen material. A grid of sensors work out the co-ordinates being touched from the change in temperature. Allows multi-touch.
Inkjet printer -
best for one-off photos or a few pages of high quality colour printing