Protocols Stack Or How Data Is Transmitted Between Computers

Before reading this article I suggest you read the previous article about the Internet 
All computers have an IP address which is like an address. When the computer wants to send information from one system to another, the IP address is used. 
Example- source system [] to destination system [ ]. We will take a standard program example. "Hello World" is sent from source system to destination system, the alphabet is changed into an electrical signal and transmitted through wires and again decrypted and back to an alphabet in the destination system. This process of chucking down the data into packet,s encrypting it, adding the port number of listing application, and adding the IP address of the destination system all are accomplhised by proctocol stacks, which is inbuilt in all OS [Operating Systems]
The protocol stack used in the internet is called TCP/IP.  It has the  following layers 
  • Application Layer - It is specific to the application where the data is created; i.e., email, MSword, notepad
  • TCP Layer - it adds the port number to the packets
  • IP Layer - The IP address of the destination system is added
  • Hardware Layer - converts the packets to network signal and transmits through the modem . [ethernet card, network card,driver's]
Each layer is another big ocean to explore, it includes how the application is built, which port number it is listening to, how the data is handled, Operating system, kernel programming, middleware, driver software.  
As a whole, all these things are used when a single email is sent and all these things are happening at the speed of light.