What is the blockchain?
Tags: blockchain, programming
Published: 2021-07-29 00:57:20

Hi. You've probably heard the popular definition: "The blockchain is a decentralized ledger" and all that stuff we really don't get.  Just in case it renders you brain-dead the way it does me, I'll keep it simple for you.


## What a block actually is

A block is an object for storing data and a blockchain is a chain of blocks. Blocks have two integral elements - code and data.
Data is passed into the block from the front end and the code (called a smart contract) defines how the block handles the data.

When a block handles its data, it stores records of the data and transactions it has carried out inside itself and when it has reached its storage limit, a new block gets created to process and store incoming data. Each new block has a link to the previous block(the block it came from) and when you look at the overall network, you see a number of blocks linked together forming a chain structure. Hence the name "blockchain."

A blockchain is, in effect, a floating database containing record of every transaction that has ever been made on it since its creation.

Now, you've probably also heard that it's decentralized so let's understand what that means.


## Decentralization

A centralized system is a system in which a single body has access to and control of all the data that flows into and out of it. In a decentralized system, all the data is accessed and controlled by everyone and no one at the same time.

In a centralized system like the banks, records of all the transactions the bank has ever done are stored in a server somewhere, are accessible by the bank and can be controlled by them.
In the blockchain however, the chain of blocks and the transaction records they contain are not stored on a single server. Rather, whenever a new computer connects to the blockchain network, it gets its own copy of the complete blockchain and the data stored on it. Also, whenever updates are made to the blockchain, every connected computer's copy of the blockchain is updated. This way, every computer that is connected to the blockchain has access to the entire blockchain and in real time.


## Security

This last paragraph could beg the question: "If everyone has access to all the data stored on the blockchain network, couldn't someone change something? I mean, isn't the blockchain said to be secure? 

Well, yes. The blockchain is secure. Once the code(smart contract) is deployed to a block, it can't be changed. The code and data are also highly encrypted - so highly encrypted that hackers wouldn't even bother.

To control a centralized system, a hacker would have to get access to the computer that stores and controls all the data but to take over a decentralized system like the blockchain, a hacker will have to take over millions of computers that are connected to the network so let's just say that it's tedious to hack the blockchain network.


So that's it. In summary,
> A block is an object that processes and stores data.
>
> The blockchain is like an ever-growing chain of blocks.
>
> A computer that's connected to the blockchain network is called a node.
>
> Every single node has real-time access to the whole blockchain 
>
> No single organization controls the data in the blockchai
>
> The blockchain is secured with heavy encryption


That's about it for this post. Do you now have a better understanding of blockchain technology?