2.1 Hardware and Communication (Protocols (UDP (User Datagram Protocol) -…
2.1 Hardware and Communication
Control Unit - Gives instructions to the other components
Data bus - Allows the transfer of data between components. Travels in any direction
Address bus - Allows memory addresses to be sent from the CPU to components
Control bus - Allows instructions to be sent from the CPU to other components
Cache - Small reserve of memory on top of or next to the CPU, comes in 3 levels.
ALU - Handles all mathematical and logical operations
Accumulator - Stores the immediate result from the ALU
Program Counter - Stores the index of the next instruction, incremented by one as each instruction is being processed
MAR (Memory address register) - Contains the address of the data
CIR (Current instruction register) - Stores the data about the instruction currently being processed
MDR (Memory data register) - Contains the actual data
CD - 500MB-900MB
DVD - 4.7GB(single), 8.5GB(double)
Blu-Ray - 25GB-50GB
Hard Drive - 500MB-6TB
Credit Card- Very Small Storage
SSD - 200GB-2TB
USB - 500MB-64GB
SD Card - 1GB-128GB
RAM (Random access memory) - Volatile memory, stores data about instructions or processes that are currently being processed
ROM (Read-only memory) - Data that cannot be edited such as the OS of a device
Fetch - Control Unit receives next instruction, stored in CIR. PC incremented by 1. MAR is set to the address, and a request is sent along the Address bus (Instruction sent to same location along the Control bus).
Execute - Data is received by the CPU from the Data bus, stored in the MDR. If a calculation is needed, data is sent to the ALU and the result is stored in the Accumulator. Anything needed to be outputted, is sent along the Data bus to the relevant component.
Parallelisation - Adding more cores to a CPU, allowing a quicker clock-speed
Pipelining - Where the next instruction is prepped, during the execution of the previous instruction. This means that no time is wasted waiting for the data to be fetched
Clock-speed - Number of instructions processed per second, measured in Hz. (1 GHz = 1 billion)
Fragmentation - When a file is broken into separate "fragments" to fill available storage. De-fragging re-organises files so that there are no fragmented files
Optical Character Recognition - A computer will read data off of a printed document, and try to interpret it. Often is wrong and is therefore needed to be proofread.
Optical Mark Recognition - Where marks on a printed document are read by the computer, which checks if there is a line there or not. Very reliable although the computer needs to be set up to read the documents first.
Magnetic Ink Recognition - Special Ink, containing iron oxide, is often used on bank notes, where a computer is set up to read the data quickly and more efficiently than OCR.
UDP (User Datagram Protocol) - Breaks data down into packets, like TCP, but doesn't involve checking such as if the data arrived.
DHCP - (Dynamic Host Configuration Protocol) - Assigns each connection its own, separate IP address
TCP (Transmission Control Protocol) - Part of the IP suite, breaks data down into packets
IP (Internet Protocol) - Allows the transfer of packets across the internet
IMAP (143) (Instant Messaging Access Protocol) - Allows emails to be received from mail servers
SMTP (25) (Simple Mail Transfer Protocol) - Directs emails from server to server
FTP (21) (File Transfer Protocol) - Allows files to be transferred across the internet
HTTP (80) (Hypertext Transfer Protocol) - Controls the transmission of data across the internet
1) When the user interacts with a webpage, the request goes through the application layer. This includes protocols like HTTP, FTP and SMTP
2) Next, in the transport layer, TCP (or UDP) is used to break down data into packets and then sends them through their designated ports (eg. HTTP = port 80)
3) In the network layer, the source and destination IP's are added, labelling which network to send the data to and where it came from.
4) Finally, in the link layer, the MAC addresses are added as well. The packets will then go through the router and follow the network
Network - A group of two or more devices, which can communicate to each other
Handshaking - When two devices are about to communicate, one will send a "are you ready?" message and wait for a reply. Once it has received this, it will transmit the data.
Hub/Switch - A central component used in Star networks, Hubs send the data to all devices, only the designated device will accept, Switch will only send data to the designated device.
Router - When a device is trying to view a webpage, a request is sent to the router. The request is received as "packets" of information, which are sent by the router up the chain to the internet provider's data centre. From there the packets are read, the data is received and sent back to the router, which then sends the data to the device and the page is displayed.
NIC (Network Interface Card) - Either wired or wireless, allows connections to a network, Uses different protocols varying in speed (A/B/G/N). N is fastest.