GCSE COMPUTER SCIENCE (OCR) TEST WITH 100% CORRECT ANSWERS.

Arithmetic Logic Unit (ALU) Performs operations on data e.g. Addition, subtraction Control Unit (CU) Coordinating activities of the CPU Brainpower Read More Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:01 / 0:15 Full screen Registers Quick, small stores of data within the CPU Memory Address Register (MAR) Holds memory address for data or a instruction about to be used by the CPU Memory Data Register (MDR) Holds actual data or instruction Accumulator Stores results of calculations in the ALU Program Counter (PC) Holds memory address of the instruction for each cycle Fetch The next instruction is retrieved by CPU from main memory Decode The instruction is broken down and decided so computer can understand Execute The CPU performs what the instructions told Embedded System A computer system built within a large device e.g. Camera, washer, car Volatile Memory loses its data when power of Non-volatile Memory retains its data when power is lost Random Access Memory (RAM) Read/write - function is to load open programs and operating system data currently in use - volatile Read Only Memory (ROM) Can only be read, can't be changed, stores essential programs to be run in order to boot the computer - non-volatile Cache A type memory that stores copies of frequently used data, much faster than RAM, lower capacity - closer to CPU Buses Collection of wires that carry signals between various components of the computer system Central Processing Unit (CPU) Processes all of the data and instructions that make the system work - can be effected by clock speed, number of cores, cache size Clock speed How fast the computer does the FDE cycle virtual memory A memory management procedure needed when the RAM is full so a temporary section is made which acts like a part of RAM Flash memory Solid state storage, non-volatile, more reliable/durable but can only be overwritten a limited number of times Graphics Processing Unit (GPU) Handles graphics and image processing Optical storage CD, DVD, Blue-ray ADV: cheap,easy to transport DIS: slow, less storage than hard drives, stored data degrades over time, cannot be written over Magnetic storage Hard drives ADV: fast access, stores large amounts of data, low cost DIS: not very portable, easily be broken Solid State storage USB, flash memory, SD ADV: fast, small, light, easily potable, quiet DIS: more expensive, storage capacity less, limited number erase/write cycles Cloud stotage Data is stored on multiple servers in a remote location ADV: secure, can be accessed anywhere, no need to buy DIS: needs internet, download and upload can be effected by internet connection, less control if data is held Operating System essential software that links the hardware and other software together and generally manages the computer system Command-line Interface Text commands where user has to type in command Graphical User Interface (GUI) uses icons and other visual indicators to navigate and issue commands Utility Software maintains a computer Defragmentation Software reorganises data on the hard drive to put fragmented files back together and moves files to collect all the free space Backup Software Full Backup - a copy is taken from from every file on the system Incremental Backup - only files created or edited since last backup are copied Compression Software reduces file size so they take up less space on hard disk Encryption Software scrambles data to stop others from accessing it Open Source Software source code is made freely available and users can modify it ADV: free, ,made for greater good, can be adapted DIS: small, buggy, security holes, no warranties, no customer support Proprietary Software only the compiled code is released and the source code is kept a secret ADV: warranties, well-tested, reliable, cheaper DIS: expensive, software may not fit user needs Personal Area Network (PAN) within the range of an individual person Local Area Network (LAN) a network that connects devices close to each other e.g. school, house Wide Area Network (WAN) a network within a large geographical area e.g. internet Bandwidth amount of data that can be transferred in a given time Network Interface Card (NIC) allow a device to connect to a network Switch connect devices on a LAN Router responsible for transmitting data between networks Ethernet a set of standards for connecting computers Client-server Network client has connection to server, servers can backup and store centrally but can be expensive and difficult to maintain Peer-to-peer Network no central server, each computer equal in responsibility, have to work as both server and a client. Star Topology ADV: better performance, rest of network not affected in one fails, simple to add more devices DIS: wire needed for all devices, expensive Mesh Topology ADV: faster DIS: expensive MAC Address assigned to all devices, unique to all devises and cannot be changed, permanent, identifies the actual device.