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Cheatography

Information Technology (Computing) Cheat Sheet (DRAFT) by

A Cheat Sheet that covers elements of Hardware, Networking and Security and more. If you identify any discrepancies, including spelling or grammar errors, please reach out into the comments.

This is a draft cheat sheet. It is a work in progress and is not finished yet.

TERMIN­OLOGY

Protocol
The fact you can read this text, means we share the protocol, the English language; it's a structure that shares common and understood princi­ples.
Standard
Standa­rdised. Techno­logies and/or concepts usually designed and maintained by instit­utions and commun­ities of the industry.
Host
This can be any device with computing capabi­lities, such like a computer, networking device, a server, etc.
Plug&Play
Describes the ability to connect an external peripheral to a computer without the need to install a device driver applic­ation. A device driver is program which enables external devices to commun­icate with the computer they're connected to.
Cloud Computing
Cloud computing simple describes a 'service', hosted by indepe­ndent, or large corporate entities offering hardware, software and other services for remote use. Google Drive, Microsoft One, IBM Cloud, AWS and iCloud are the very well know providers of Cloud offerings, hardware and software etc, as a service.

HARDWARE

CPU
Central Processing Unit
The component considered the 'brain' of a computing device, respon­sible for perfor­min­g/e­xec­uting (calcu­lating) the comman­ds/­ins­tru­ctions of software programs loaded into and out of RAM.
A CPU contains multiple sub-co­mpo­nents, such as a APU (Arith­metic Processing Unit), Cache memory and most often, an integrated GPU (Graphical Processing Unit) for rendering 2D and 3D imagery.
RAM
Random Access Memory
The CPU requests the inform­ation from storage (where your programs are stored) and loads them into memory (RAM) for proces­sing. The CPU will then execute (calcu­late) those instru­ctions and place the results back into RAM. Because of this close relati­onship of back-a­nd-­fourth, RAM has a direct relati­onship with the CPU.
RAM comes in various size form-f­actors and is described as a 'volatile' form of storage, meaning it will lose all the inform­ation it contains once power is removed.
Cache
Super-fast memory contained within the CPU.
Cache sizes are small in bit-size, however because of its speed, this has less impact.
Cache is broke down into Levels, known as L1, L2 and L3 sections. Each 'core' within a CPU have their own L1 and L2 Caches, while all cores share the L3 available resource.
HDD/SSD
Hard Disk Drive/­Solid State Drive
Both are forms of 'non-v­ola­tile' storage and are the techno­logies used for storing the computers' Operating System and a users' files, such like documents, photos etc. Each type of technology has their Pros and Cons.
A HDD is a mechanical form of storage and uses 'spinning platters' and an 'actuator arm' to read and write data using a magnetic process. An SSD has no moving parts and is simply a circuit board containing storage chips (usually NAND) to perform the same functions. Both techno­logies can use either the 'SATA' or 'PCIe/­NVMe' commun­ication bus standards.
eMMC
embedded Multi-­Media Card
A form of storage media, consisting of NAND flash chips and a storage contro­ller.
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NVMe
Non-Vo­litile Memory express
A very fast standard of data commun­ica­tion, using the NVMe bus protocol standards to perform its speeds.
NVMe is superior to the more commonly adopted 'SATA' standard. 'Compact Flash express' (a form of storage media) uses the NVMe/PCIe standards for commun­ica­tion.
BIOS
Basic Input/­Output System
A small chip on the mother­board which contains its firmware. The BIOS is the very first single piece of software to be loaded into memory. Before the BIOS initiates the Operating System, the 'POST' (Power On Self Test) is performed, which tests the available hardware and their respective health.
The BIOS chip is powered by a small CMOS (Compl­eme­ntary Metal-­Oxide Semico­ndu­ctor) flat-cell battery to retain system settings, such like the date/time and boot drive sequence.
TPM
Trusted Platform Module
The intern­ational standard for designing secure crypto­-pr­oce­ssors.
With this standard in mind, a TPM is a small chip that typically resides on the mother­board of a computer, that generates a crypto­graphic key (a numbered value) and assigns this to the hardware components within that host.

MISCEL­LANEOUS

Kernel
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Considered the heart of the Operating System and is the first component of the OS to be loaded into memory.
The Kernel is the component closest to the hardware of the computer, respon­sible for the disk drive, file, memory and process manage­ment, etc.
ISO Image
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A single file which contains the entire contents of an optical disk, including the folder and file hierarchy.
ISO images are the foundation of a bootable CD, DVD or USB drive. However, a boot program must be added by using a utility program to 'flash' the media. For example, WinISO makes CDs and DVDs bootable from ISO images, while Rufus does the same for USB drives. Balena's 'Etcher' utility program can also flash USB drives, as well as SD card media.
FAT32
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A file system structure. Most USB's use FAT32 by default, because of its wider compat­ibility with new and old hardware. This default file system can be changed by reform­atting the drive.
Maximum file size is 4GB. If using a USB drive to install an Operating System, (live media) FAT32 is not recomm­ended due to its small file structure archit­ecture.
API
Applic­ation Progra­mming Interface
Like a 'Graphical User Interface' (GUI) connects a user to a computer, an API logically connects one applic­ation to another.
The applic­ation can refer to stand alone software, part of a server, or server as a whole.
VM
Virtual Machine
A technology (software based) that enables an Operating System to be hosted within another, of which is called a 'Guest OS'.
The hardware on your host, is segmented and shared between the Virtual Machines it hosts.

NETWORKING

TCP/UDP
Transm­ission Control Protoc­ol/User Datagram Protocol
Both TCP & UDP are the most commonly standard of how computers commun­icate with each other over a network, including the wider Internet. TCP is a 'Conne­ction Oriented' protocol, meaning it guarantees the delivery and rearra­ngement of the data packets involved during the whole transm­ission process.
UDP is 'Conne­cti­onless' and is considered a 'fire and forget' protocol, because it does not guarantee the delivery nor the correct rearra­ngement of the data packets. UDP however, is faster than that of TCP and therefore works well for the demands of video and gaming.
Hub
Networking device
Device used to connect one or more hosts to the network.
A Hub is considered obsolete and dumb, because it does not learn what device resides on a given port; and therefore, will 'broad­cast' traffic to every device connected to it.
Switch
Networking device
An intell­igent version of the 'Hub' used to connect one or more hosts to the network.
A Switch uses the ARP table (Address Resolution Protocol) to recognise what device is on what connected port to exchange that inform­ation to the approp­riate device.
Router
Networking device
The purpose of the Router is to 'route' data between networks separate from its own.
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Proxy
Networking device
To act on behalf of another. A proxy server is designed to perform actions, such as data packet forwarding on behalf of a host, or other server.
A 'reverse proxy' typically sits between the host requesting inform­ation and the server respon­ding. The purpose of this is to withhold the IP address and other critical inform­ation from the host.
Gateway
Networking device
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DNS
Domain Name Server­/System
A protocol used to resolve IP addresses to humanly readable domain names, e.g. cheato­gra­phy.com and vice-v­ersa.
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DHCP
Dynamic Host Config­uration Protocol
A set of protocols used to assign a host the inform­ation it needs to commun­icate over a network.
Provides a host with an IP address, subnet, gateway and DNS inform­ation. IPs are leased, meaning they are tempor­arily assigned to a host by the DHCP server for a specified amount of time, at the discretion of the device's admini­str­ator.
CDN
Content Delivery Network
Considered the 'backbone' of the Internet, consisting of many proxy servers hosted in data centres around the world to deliver Internet content quickly to end users.
CDN's are maintained by large corpor­ates, which offer these techno­logies as a service to other brands and busine­sses. Well known CDN providers include, Cloudf­lare, Fastly, AWS Cloudfront and Stackpath.
HTTP/HTTPS
Hyper-text Transfer Protoc­ol/­Secure
The standards for commun­ica­tions between websites and servers.
HTTP is not secure, meaning these types of websites you visit are not encrypted. HTTP uses port 80. HTTPS is the secure variant of HTTP and uses TLS (Transport Layer Security) to encrypt the data exchanged and uses port 443.
URL
Uniform Resource Locator
Also knows as an Internet address or a web address, a URL is a standard for the naming convention for addressing documents accessible over the Internet or Intranet.
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Port Numbers
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Standard of assigning and organising various protocols used within Networ­king. Consists of reserved and dynamic ports.
Any form of data/t­raffic can be sent down any port, providing the receiving device is listening for that traffic on said port.
Cookies
A small piece of data placed on your device by the websites you visit
There are typically two types of Cookies commonly used by websites, 'session' and 'tracking' cookies.
Session cookies are used to remember your visit to a site and the prefer­ences you set. This is partic­ularly useful for online shopping should you have items in your basket. Tracking cookies are considered bad and is used by advert­ising and marketing companies to collect details about your machine, online habits and browsing history to feed you tailored advert­ise­ments.
BGP & ASes
Boarder Gateway Protoc­ol/­Aut­onomous Systems
BGP describes the 'Postal Service' of the Internet, delivering data as fast and as efficient as possible, by looking for the best available route for traffic to take.
ASes describes the Internet as networks of networks - through the use of routers, (Auton­omous Systems) and maintained by ISPs, CDNs and individual organi­sat­ions.
Intranet
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While the Internet is a collection of networks on a mass scale, an Intranet is a large internal network usually associated with corpor­ates, which gives employees access to company resources.
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SECURITY

Air gapped­/Fa­raday cage
In computing security, an air gapped host is a device which does not have any connec­tio­n/c­omm­uni­cation with any other networks outside of its' own, including that of the Internet.
Faraday cage describes a perimeter (usually a room or a building) that is purposely designed to prevent wireless freque­ncies of any type to enter or leave.
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