Computing Topics to Revise

  • Created by: brynclark
  • Created on: 07-06-17 14:07
Control Unit
Controls and coordinates the activities of the CPU, directing the flow of data between the CPU and other devices
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Address Bus
When the CPU wants to access a particular main memory location, it sends the address to memory via this
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Data Bus
Used to send data from memory to the CPU and visa versa
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Control Bus
Used to send control signals from memory to the CPU and visa versa
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Arithmetic Logic Unit
Performs arithmetic (ADD, SUB) and logical (OR, AND) operations on data
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Program Counter
Holds the address of the next instruction to be executed
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Current Instruction Register (CIR)
Holds the current instruction being executed, divided into operand and opcodes
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Memory address register
Memory Address Registers Holds the location in memory (address) of the next piece of data or program to be fetched (or stored).
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Memory Data Register
Temporarily hold instructions fetched from memory
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Small instruction set, fewer transistors needed, cheaper to produce
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Larger instruction set, used to perform tasks in a few lines of assembly code
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A specialised CPU that is used for rendering graphics, designed to perform simple instructions of small amounts of data
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Virtual Memory
When the hard disk is used as an extension of primary storage (RAM), e.g. when MS Word is open but you're not using it
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OS - Multi-tasking
CPU switches from one program to another quickly to give the appearance of multi-tasking
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OS - Multi-user
Allows more than one person to share a computer's resources at the same time by a mainframe computer
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OS - Distributed
Combines the power of multiple computers, presenting them to the end user as if they were a single system
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OS - Embedded
Carry out a single function, low powered CPUs and little RAM, e.g. card machines
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OS - Real-time
Carry out a process in a guaranteed amount of time, e.g. safety critical systems
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Low-level assembly language to machine code, processor specific
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Looks at each line of source code, if there are no syntax errors, it translates and runs it
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Translates all the source code and translates it into object code
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SoC 1 - Lexical Analysis
Removes blank spaces and comments
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SoC 2 - Syntax Analysis
Checks the syntax of the code against the rules
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SoC 3 and 4 - Code Generation and Optimisation
High level code translated into machine code statements, optimisation techniques reduces execution time
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Links the instructions from external subroutines into memory
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Load the external object code anywhere in memory
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Pre-compiled programs that can be run when needed, saves time for the programmer
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Direct Addressing
The address given is the location of the data to be used. E.g. LDA 43 loads the contents of memory location 43 into the accumulator
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Indirect Addressing
The Address given is the memory location that holds the location of the data. E.g. if the memory location 43 contains the value 119, then the value in the memory address 119 is loaded into the accumulator
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Indexed Addressing
The value given is added to the value stored in the index register to give the memory location. E.g. if the value in the index register is 100, LDA 43 will take the value in the memory address 143 and load it into the accumulator
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Immediate Addressing
The Address given is not actually an address but the required value. LDA 43 would mean load the value 43 into the accumulator
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A template used to define an object. It specifies the methods and attributes an object should have
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An instance of a class
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A subroutine associated with an object. “new” is a special type of method called a constructor. Constructors define how an object is created
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Variables contained within and associated to an object
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Ensuring private attributes can only be amended through public methods. This prevents objects from being manipulated in unintended ways
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The ability for a class to inherit the methods and attributes of a parent class. It’s ‘child’ class can have its own methods and attributes and override methods of its parent class
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Meaning ‘many forms’, is the ability for objects of different classes to be treated in the same way, e.g. different methods maybe applied to different objects of different classes
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Lossless Compression - Dictionary Coding
Builds and index containing every data item and an index reference. The compressed file consists of the index, and the sequence of occurrences
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Lossless Compression - Run Length Encoding
All that is stored is the data item along with how many times it is repeated, common with storing images
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Symmetric Encryption
Same key used to encrypting and decryption, danger of interception or key generation
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Asymmetric Encryption
Different keys for encryption and decryption, known as public and private keys, more secure
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ACID - Atomicity
A change to a database is either completely performed or not at all, a half-completed change MUST NOT be saved back to the database
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ACID - Consistency
Any change in the database must retain the overall state of the database
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ACID - Isolation
A transaction must not be interrupted by another transaction, it must occur in isolation so that other users or processes cannot have access to the data concerned
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ACID - Durability
Once a change has been made to a database it must not be lost due to a system failure
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Domain Name System (DNS)
Identifies the area or domain that an internet resource resides in e.g. ""
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Bus Topology
All the computers are connected to a single cable. The ends of the cable are plugged into a terminator
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Star Topology
Has a central node, which maybe a switch or a computer which acts as a router to transmit messages. A switch keeps a record of all the MAC addresses of each device on the network so it can identify which computer to send data.
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Mesh Topology
Each node is connected to every other node, only one node requires a connection to the internet in order to share this connection.
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Circuit Switching
Circuit switching creates a direct link between two devices for the duration of the communication. E.g. Public telephone system. Packets must be sent and received in the same order
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Packet Switching
This is a method of communicating packets of data across a network on which other similar communications are happening simultaneously. Data arrives in a series of packets and is reassembled.
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TCP/IP Stack
Used worldwide to enable computers to communicate regardless of location.
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TCP/IP - Application
Uses protocols relating to the application being used, e.g. HTTP for the browser.
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TCP/IP - Transport
Packets are split and labelled with the port and where it is in the sequence.
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TCP/IP - Network
Adds the IP address so it can be routed to the correct device, the addition of the IP address to the port number forms a socket that specifies which device the packet is being sent to and the application to be used.
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TCP/IP - Link
Physical connection between network nodes. It adds the unique MAC Address and identifies the network interface cards of the source and destination computers.
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File Transfer Protocol (FTP)
FTP is a very efficient method of transferring data across a network. Works as a high level protocol in the application layer using the appropriate software.
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Filter communications in and out of networks using a set of rules
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Another physical computer placed between a network and a remote source, configured as a hardware firewall
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Network Interface Cards (NIC)
Receive and send electrical signals across a network, designed to work with standards e.g. Ethernet
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Used to connect networks, receives packets and forwards them to the correct location
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A device to connect devices together on a network, makes use of physical hardware MAC addresses
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A connectivity device that broadcasts a signal to all possible destinations at once
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Wireless Access Points (WAP)
Makes use of wireless to connect a node to a Wi-Fi network
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Transmission Media
Physical medium to transmit data, older slower coaxial copper cables, and quicker fibre optic cables
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Search Engine Indexing
The actual process of a particular search engine, collecting, sorting, and storing data into its index
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PageRank Algorithm
Compiles and ranks website pages and results list when you perform a search
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A static data structure that stores multiple items that are the same data type under a shared common name
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A collection of related fields under one name, a field is a variable and each one can have a different data type
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An immutable list, cannot be changed once created
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An abstract data type consisting of a number of items in which the same item can occur more than once
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Linked List
A dynamic data structure used to hold a sequence, each item contains a data field and a pointer
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A set or vertices/nodes connected by edges. Edges can may be one way or two way and can also be weighted
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A first in first out (FIFO) data structure, items are added to the rear and retrieved from the front
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A last in last out data structure (LIFO), items are pushed on the top and popped as well from the top
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Used to store hierarchical data, represented as an array with the data, a subtree pointer and pointers to other nodes at the same level
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Hash Table
An array, coupled with a hash function, a hash function manipulates the data and the hash value is stored in the table
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Half Adder
A circuit that takes a 2-bit input and outputs the binary sum of the two inputs, connects an AND and a XOR gate
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Full Adder
Combines two half adders, enables a 3 bit input that outputs the sum and the carry bit
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Concatenating Full Adders
Connect n full adders together means you can add a binary number of n bits
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D-Type Flip Flops
A sequential logic circuit that can store one bit and flip between two states, two inputs, a control input and a clock signal
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Other cards in this set

Card 2


When the CPU wants to access a particular main memory location, it sends the address to memory via this


Address Bus

Card 3


Used to send data from memory to the CPU and visa versa


Preview of the back of card 3

Card 4


Used to send control signals from memory to the CPU and visa versa


Preview of the back of card 4

Card 5


Performs arithmetic (ADD, SUB) and logical (OR, AND) operations on data


Preview of the back of card 5
View more cards


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