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1 - Theory of Computer Science / Data Transmission
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The Internet
Like it or loathe it, the Internet is here to stay. The internet now plays such a huge part in our daily lives that if somebody took it away we probably would have forgotten how things were done before it was invented and revert back to living in caves.... ok maybe its not quite that extreme, however do you know how to correctly read a map, find somebody in a phone book?
What is the internet?
When asked this question many people will often begin to struggle as they realise that they cannot describe the thing that is so involved in their daily lives. The Internet = The worlds largest network, it is a series of inter-connected networks Often the internet is confused with the World Wide Web, be careful, they are not the same thing! The World Wide Web = A collection of web pages and documents that can be accessed via the internet. Web pages are accessed by the user through software called a web browser. When asked about this be careful not to use brand names i.e. Chrome or Safari. |
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ISP - Internet Service Provider
ISP stands for Internet Service Provider. An ISP is the company that provides you with access to the Internet.
ISP stands for Internet Service Provider. An ISP is the company that provides you with access to the Internet.
Cookies
Cookies are small text files that are placed onto a client computer, usually when accessing a web page. The text file is stored on the client (users) computer and it is placed there by the web browser. This text file will store data or files related to the users experience of the visited web page. The next time that the user visits this website, the website will detect the presence of the cookie and then read the contents before adjusting the web experience appropriately.
This text file can be beneficial to a user as it can store your personal preferences, store items in a virtual shopping basket or store your login details.
WARNING - Cookies can sometimes be exploited by spyware that can read the content of a legitimate cookie file and send it off to the malware creator for malicious use. This is why it is often advisable to disable cookies.
Cookies are small text files that are placed onto a client computer, usually when accessing a web page. The text file is stored on the client (users) computer and it is placed there by the web browser. This text file will store data or files related to the users experience of the visited web page. The next time that the user visits this website, the website will detect the presence of the cookie and then read the contents before adjusting the web experience appropriately.
This text file can be beneficial to a user as it can store your personal preferences, store items in a virtual shopping basket or store your login details.
WARNING - Cookies can sometimes be exploited by spyware that can read the content of a legitimate cookie file and send it off to the malware creator for malicious use. This is why it is often advisable to disable cookies.
Uses of Cookies
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Cookies themselves actually play a very important role in ensuring we get the useful internet experience that we are used to. Some of these uses include:
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URL - Uniform Resource Locator
URL stands for Uniform Resource Locator. The URL is essentially the web address that you type into your web browser, This web address pints to the website that you wish to visit.
The URL is actually broken down into three main sections by the browser when attempting to access the site. These are:
https://www.bitsofbytes.co/home.html
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HTTPS:// This part of the URL is the Protocol. It refers to which protocol will be used e.g. HTTP or HTTPS |
www.bitsofbytes.co This part of the URL is the Domain / Web server's name. This is actually converted into a 32 bit ip address. |
home.html This part of the URL is the File name. It refers to the file that you are trying to receive from the web server (Often a web page) |
DNS - Domain Name Server
A domain name server can be thought of as the phone book of the internet.
An IP address is the address given to every device connected to the internet. This address is used to find the correct server / device when trying to connect to a device or web page.
IP addresses are in number form e.g. 192.168.0.1
Web site addresses (URLs) are more human friendly e.g. www.bitsofbytes.co
The role of a DNS
Like a phone book the DNS essentially stores a large list of URLs along with their corresponding IP addresses.
When a user types a URL into their web browser and clicks to visit it the ISP will take it to the DNS.
The DNS will convert the URL into an IP address and then direct your traffic towards it.
An IP address is the address given to every device connected to the internet. This address is used to find the correct server / device when trying to connect to a device or web page.
IP addresses are in number form e.g. 192.168.0.1
Web site addresses (URLs) are more human friendly e.g. www.bitsofbytes.co
The role of a DNS
Like a phone book the DNS essentially stores a large list of URLs along with their corresponding IP addresses.
When a user types a URL into their web browser and clicks to visit it the ISP will take it to the DNS.
The DNS will convert the URL into an IP address and then direct your traffic towards it.
Hardware for the Internet
Inorder to connect to the internet some specialist hardware is required, this includes a Router, Modem and a NIC (Network Interface Card).
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Router
The router is a piece of hardware that is common in most house holds. Its purpose is to allow many devices to share one single internet connection. Without this every device would need its own internet connection. It will also direct data to and from the correct devices. |
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Modem
As we already know from the data representation unit, computers can only work with digital information. This could cause an issue when transmitting digital information across the internet as the phone cables used will send information in analogue form! To solve this problem the modems purpose is to convert the digital signals of a computer system into analogue signals that can travel across phone lines and vice versa. |
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Network Interface Cards
A Network Interface Card, sometimes referred to as a Wireless Network Interface Card (WNIC) is a piece of hardware that is necessary for any device to be connected to a network. It provides an place for physical or wireless connection i.e. copper cable, fiber optic or radio waves. Each NIC has a unique MAC address assigned to it. It is also possible for a NIC to have 2 MAC addresses for example, 1 MAC for a wired connection and another MAC for the wireless connection. |
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MAC Addresses
The MAC (Media Access Control) address is assigned to every NIC by the company that manufactured it.
A MAC address consists of 12 Hexadecimal Characters:
4F:5A:16:5D:2A:5B
The first 6 (Left side) values of the MAC address identify the manufacturer e.g. Apple, Sony...
The last 6 (Right side) values of the MAC address identify the device itself.
A MAC address is unique to each device, there are 2^48 possible addresses. Unlike an IP address, the MAC address will always remain the same.
The MAC (Media Access Control) address is assigned to every NIC by the company that manufactured it.
A MAC address consists of 12 Hexadecimal Characters:
4F:5A:16:5D:2A:5B
The first 6 (Left side) values of the MAC address identify the manufacturer e.g. Apple, Sony...
The last 6 (Right side) values of the MAC address identify the device itself.
A MAC address is unique to each device, there are 2^48 possible addresses. Unlike an IP address, the MAC address will always remain the same.
Protocols of the Internet
Protocols are essentially a set of rules. For the internet to work effectively different protocols have been set up to ensure its smooth operation.
Some of the most important protocols are:
TCP/IP
HTTP/HTTPs
IP
Some of the most important protocols are:
TCP/IP
HTTP/HTTPs
IP
TCP/IP
TCP/IP stands for Transmission Control Protocol / Internet Protocol.
TCP/ IP is responsible for ensuring that data can be transmitted across the internet using a system called packet switching.
This video from www.code.org does a really good job at explaining packet switching and TCP/IP
TCP/IP stands for Transmission Control Protocol / Internet Protocol.
TCP/ IP is responsible for ensuring that data can be transmitted across the internet using a system called packet switching.
This video from www.code.org does a really good job at explaining packet switching and TCP/IP
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Key Points from the video
TCP/ IP packets contain the following informaiton: IP address of the recipient IP address of the sender Number of Packets being sent Packet secuece number (E.g. 5 /65) |
Packet switching = The breaking down of large files into smaller pieces (Packets). Each packet can travel to its destination taking a different route. Upon recieving all of the packets, TCP will check that all packets have been recieved. If any packets are missing, a request will be sent back the the sender asking for the missing packet(s) to be resent.
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HTTP / HTTPS
HTTP stands for Hyper Text transfer protocol, it is used when accessing web pages.
This protocol is what requests that the web server (Computer that stores websites) uploads the requested website to your web browser.
HTTPS is the secure version of HTTP, The difference between HTTP and HTTPS is that all data is encrypted, this encryption is essential for online banking or shopping websites where bank and personal details could be intercepted. The use of HTTPS is fast increasing across the internet.
www.code.org have produced another great video that explains this protocol.
HTTP stands for Hyper Text transfer protocol, it is used when accessing web pages.
This protocol is what requests that the web server (Computer that stores websites) uploads the requested website to your web browser.
HTTPS is the secure version of HTTP, The difference between HTTP and HTTPS is that all data is encrypted, this encryption is essential for online banking or shopping websites where bank and personal details could be intercepted. The use of HTTPS is fast increasing across the internet.
www.code.org have produced another great video that explains this protocol.
IP Addresses
Any device connected to the internet, whether its your desktop PC, Laptop, Tablet, Smartphone or games console must have its own IP address. The IP address is given to the device by the network or the ISP.
One of the main reasons for having an IP address is to ensure that devices can be identified when on a network / the internet.
Each device will have 2 different IP addresses, these are:
Private IP address - This is the IP address of the device within the Devices LAN (Local Area Network)
Public IP Address - This it the Address that belongs to your router.
Data requested by a device on a local network will first be received at the Routers Public IP, The router will then sent the data to the correct device using the private IP address.
Any device connected to the internet, whether its your desktop PC, Laptop, Tablet, Smartphone or games console must have its own IP address. The IP address is given to the device by the network or the ISP.
One of the main reasons for having an IP address is to ensure that devices can be identified when on a network / the internet.
Each device will have 2 different IP addresses, these are:
Private IP address - This is the IP address of the device within the Devices LAN (Local Area Network)
Public IP Address - This it the Address that belongs to your router.
Data requested by a device on a local network will first be received at the Routers Public IP, The router will then sent the data to the correct device using the private IP address.
IPv4 & IPv6
IP addresses for a long time have been using the IPV4 standard.
IPV4 IP addresses consist of 32 bits. These 32 bits are separated into groups of 8 separated with a "."
11111111.11111111.11111111.11111111
This is usually presented to humans in denary format. Each group of 8 having a maximum number of 255:
255.255.255.255
With IPV4 addresses using only 32 bits it means that the system is limited to a possible 4 billion (approx) unique addresses. With the internet constantly growing along with the number of possible"connected" devices a new system is under development. This system is called IPV6.
IPV6 increases the number of bits used which in turn increases the number of possible unique addresses available.
IPV6 uses a 128 bit long address number. This number is split into 8 groups of 4 hexadecimal digits, these groups are separated by colons e.g.
ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Using an address of this length will allow for a possible 340,282,366,920,938,463,463,374,607,431,768,211,456 unique addresses. This should be enough to cover all connected devices for quite some time.
IPV6 is not currently in use but it is estimated that by January 2020 it will be being used.
IPV4 IP addresses consist of 32 bits. These 32 bits are separated into groups of 8 separated with a "."
11111111.11111111.11111111.11111111
This is usually presented to humans in denary format. Each group of 8 having a maximum number of 255:
255.255.255.255
With IPV4 addresses using only 32 bits it means that the system is limited to a possible 4 billion (approx) unique addresses. With the internet constantly growing along with the number of possible"connected" devices a new system is under development. This system is called IPV6.
IPV6 increases the number of bits used which in turn increases the number of possible unique addresses available.
IPV6 uses a 128 bit long address number. This number is split into 8 groups of 4 hexadecimal digits, these groups are separated by colons e.g.
ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Using an address of this length will allow for a possible 340,282,366,920,938,463,463,374,607,431,768,211,456 unique addresses. This should be enough to cover all connected devices for quite some time.
IPV6 is not currently in use but it is estimated that by January 2020 it will be being used.
HTML and CSS
HTML stands for Hyper Text Markup Language
HTML is the language in which web pages are written in. HTML has been made the international standard for web pages. This is important as it allows the web browser to easily understand and display web pages no matter which part of the world it was created / hosted in.
If for example each country had their own different version of HTML it would make the internet a less cohesive place as lots of translation would have to occur.
CSS stands for Cascading Style Sheet
CSS works in conjunction with HTML. HTML is the code that controls the content of a website along with how it will function. CSS is different as it dictates the style and look of a web page.
Too learn more about how HTML and CSS work, I strongly suggest that you try out the www.codecademy.com HTML course.
HTML is the language in which web pages are written in. HTML has been made the international standard for web pages. This is important as it allows the web browser to easily understand and display web pages no matter which part of the world it was created / hosted in.
If for example each country had their own different version of HTML it would make the internet a less cohesive place as lots of translation would have to occur.
CSS stands for Cascading Style Sheet
CSS works in conjunction with HTML. HTML is the code that controls the content of a website along with how it will function. CSS is different as it dictates the style and look of a web page.
Too learn more about how HTML and CSS work, I strongly suggest that you try out the www.codecademy.com HTML course.
