Chapter 3 Definitions Flashcards
Define CPU
Central Processing Unit
Responsible for the execution or processing of all the instructions and data in a computer
Define integrated circuit
A chip made from a semiconductor material which carries out the same tasks as a larger circuit made from individual components
Define von Neunmann architecture
A type of computer architecture which introduced the concept of the stored program in the 1940s
Define ALU
Arithmetic and Logic Unit
The component of the CPU that carries out all arithmetic and logical operations
Define ACC
Accumulator Register
Temporary general-purpose register that stores numerical values at any part of a given operation
Define MAR
Memory Address Register
A register that stores the address of the memory location currently being read from or written to
Define CIR
Current Instruction Register
Register that stores the current instruction being decoded and executed
Define MDR
Memory Data Register
A register that stores data that has just been read from memory or data that is about to be written to memory
Define PC
Program Counter
A register that stores the address where the next instruction to be read can be found
Define control unit
The component of a computer’s CPU that ensures synchronisation of data flow and programs throughout the computer by sending out control signals along the control bus
Define system clock
Produces timing signals on the control bus to ensure synchronisation takes place
Define clock cycle
Measured in terms of GHz; this is the vibrational frequency of the system clock which sends out pulses along the control bus
Define IAS
Memory that holds all data and programs needed to be accessed by the control unit
Define backing store
A secondary storage device used to store data permanently even when the computer is powered down
Define cache
Temporary memory using static RAM to hold frequently used data/instructions by the CPU thereby increasing CPU performance.
Any area of storage used to quickly access frequently-used data
Define register
Temporary component in the CPU which can be general or specific in its use; it holds data or instructions as part of the Fetch–Decode–Execute cycle
Define address
A label for a memory location used by the CPU to track data
Define memory location
A numbered place in memory where values can be stored
Define system buses
A connection between major components in a computer that can carry data, addresses or control signals
Define address bus
The system bus that carries the addresses throughout the computer system
Define data bus
The system bus that allows data to be carried from CPU to memory (and vice versa) or to and from input/output devices
Define control bus
The system bus that carries signals from control unit to all other computer components
Define unidirectional
Can travel in one direction only; used to describe data
Define bidirectional
Can travel in both directions; used to describe data
Define word
A group of bits used by a computer to represent a single unit
Define overclocking
Changing the clock speed of a system clock to a value higher than the factory/recommended setting
Define core
A unit on a CPU made up of an ALU, control unit and registers; a CPU may contain a number of cores
Define Fetch-Decode-Execute Cycle
Cycle in which instructions and data are fetched from memory, decoded and finally executed
Define Basic input/output System (BIOS)
A suite of programs on firmware that are used to perform the initialisation of a computer system during the boot-up process
Define opcode
Part of a machine code instruction that identifies what action the CPU has to perform
Define operand
Part of a machine code instruction that identifies what data is to be used
Define instruction set
The complete set of machine code instructions used a particular microprocessor
Define embedded system
Combination of hardware and software designed to carry out a specific set of functions
Define barcode
A series of dark and light lines of varying thickness used to represent data; the code has to be scanned using laser or LED light source
Define key field
The field that uniquely identifies a record in a file
Define QR code
Quick Response Code - a matrix of dark and light
squares which represent data; the pattern can be read and
interpreted
Define frame QR code
A type of QR code that includes a space for advertising
Define DAC
Digital to analogue converter - device that converts digital data into electric currents that can drive motors, actuators and relays
Define ADC
Analogue to digital converter - device that converts
analogue data into a form understood by a computer
Define CCD
Charge couple device - a light sensitive cell made up of millions of tiny sensors acting as photodiodes
Define virtual keyboard
An onscreen keyboard which uses the features of the touch screen to emulate a physical keyboard
Define touch screen
A screen that allows the user to select or manipulate a screen image using the touch of a finger or stylus; touch screens most frequently use capacitive, infrared or resistive technology
Define RSI
Repetitive strain injury - Pain felt in the muscles,
nerves and tendons caused by a repetitive action
Define optical mouse
A pointing device that uses a red LED to track the movement of the device and then relays its coordinates to a computer
Define pointing device
An input device that allows the user to control the movement of an onscreen cursor or to allow onscreen selection by clicking a button on the device
Define CMOS
Complementary metal oxide semi-conductor - a chip that generates an electric current (or pulses) when light falls on its surface
Define DSP
Digital signal processor - A processor that calculates, for example, the coordinates of a pointing device based on the pulses of electricity received
Define optical character recognition
Technology that can convert hard copy text or images into a digital format to be stored in a computer memory
Define CAD
Computer sided design - software used to create drawings
Define CT scanner
Computed tomographic scanner - technology that can create a 3D image of a solid object by slicing up the object into thin layers (tomography)
Define capacitive touch screen
Type of touch screen that uses the change in the screen’s capacitance
when it is touched by a finger or stylus
Define infra-red touch screen
A type of touch screen that uses infra-red beams and sensors to detect where the screen has been touched
Define resistive touch screen
Type of touch screen that uses two conductive layers which make contact where the screen has been touched
Define actuator
An output device that converts electrical energy into mechanical movement
Define DMD
Digital micromirror device - A chip that uses millions of tiny mirrors on its surface to create a video display
Define thermal bubble
Inkjet printer technology whereby tiny resistors create heat and form an ink bubble which is ejected onto paper in an inkjet printer
Define piezoelectric crystal
A crystal located in an ink reservoir within an inkjet printer; the crystal vibrates and forces ink out onto paper
Define direct 3D printing
A 3D printing technique in which the print head moves in the x, y and z directions
Define binder 3D printing
A 3D printing method that uses a twostage pass; the first stage uses dry powder and second stage uses a binding agent
Define cathode
A negative electrode
Define anode
A positive electrode
Define OLED
Organic LED - light-emitting diode that uses the movement of electrons between a cathode and an anode to produce an on-screen image; it generates its own light so no backlighting is required
Define loudspeaker
An output device that converts electric current into sound
Define memory
The devices within the computer that are directly accessible by the CPU; there are two types of memory – RAM and ROM; memory is different to hard disk drives, for example, which are known as storage devices
Define RAM
Random Access Memory - primary memory that can be written to or read from
Define ROM
Read-only Memory - primary memory that cannot be written to (changed) and can only be read
Define DRAM
Dynamic RAM - a type of RAM chip that needs to be
constantly refreshed
Define SRAM
Static RAM - a type of RAM chip that uses flip flops and doesn’t need to be constantly refreshed
Define volatile
Describes memory that loses its contents when the power is turned off
Define refresh
Recharge every few seconds in order to maintain charge; for example with a device such as a capacitor
Define flip flop
Electronic circuit with only two stable conditions
Define latency
The lag in a system; for example, the time it takes to find a track on a hard disk, which depends on the time it takes for the disk to rotate around to its read-write head
Define SSD endurance
The total guaranteed number of times data can be written to or read from a solid state drive (SSD) in its usable life cycle
Define optical storage
A type of storage that uses laser light to read and write data, and includes CDs, DVDs and Blu-ray discs
Define dual layering
Using two recording layers in storage media such as DVDs and some Blu-rays
Define virtual memory
A memory management system that makes use of secondary storage and software to enable a computer to compensate for the shortage of actual physical RAM memory
Define disk thrashing
A problem in a HDD caused by excessive swapping in and out of data
causing a high rate of head movements during virtual memory operations
Define thrash point
The point at which the execution of a program comes to a halt because the system is so busy moving data in and out of memory rather than actually executing the program
Define data redundancy
The unnecessary storing of the same data on several storage devices at the same time
Define cloud storage
A method of data storage where data is stored on offsite servers; the physical storage may be on hundreds of servers in many locations
Define NIC
Network interface card - a hardware component that is required to allow a device to connect to a network, such as the internet
Define router
A device that enables data packets to be moved between different networks
Define static IP address
An IP address that doesn’t change
Define MAC address
A unique identifier which acts as a network address for a device; it takes the form NN-NN-NN-DD-DD-DD, where NN is the manufacturer code and DD is the device code
Define dynamic IP address
A temporary IP address assigned to a device each time it logs onto a network
Define dynamic host configuration protocol (DHCP)
A server that automatically provides and assigns an IP address
