Transactions in BlockChain

[aviorn36]

Hi All, I am still on timestamp 3:01:30 and I have a doubt I tried googling stuffs but it created more doubts, hoping anyone can explain it to me in better way.

1. Are there more than one transaction in the block before it get added? If yes, how will the data be represented in the block for the miner to solve the problem to find the nonce?
2. Can partially filled block be added to blockchain? If yes, can that block again have transaction added in which case data for that block would change as well as it nonce (would this change block author)?

I guess my fundamentals was not that clear on how transaction are collected and added as a block in blockchain network. Any suggestion would be greatly appreciated :)

[othaime-en]

Hey @aviorn36
Blocks just like their name are blocks/groups of transactions. A block normally contains a collection of several transactions stored in hash format and once a block is mined, you cannot add any transactions to it. That's the defining feature of a blockchain, immutability. Any new transactions that come in after a block is mined are added to the next block and so on. Transactions and their data are normally represented in hash format to make it easy to store them. When several transactions are grouped together to form a block, miners come together to solve a computational problem for example: find a hash that starts with 10 zeros. This computation helps come with the nonce for the block. This nonce is what helps guarantee the block immutability because it is added to the hashed block such that any change in the block data will result in an error because a new nonce will have to be computed again. So once a block is mined (nonce for the block data is computed), that's itYou can't add a new transaction to the block

[aviorn36]

Thanks @othaime-en. This clears out my doubt. I have few more doubts with me, i guess it will be better if i as that as separate Q&A chain. Hoping if you can help me there too.

[othaime-en]

Yeah sure. Open a new discussion I'll look into it.

[krakxn]

1: Yes, there are numerous transactions in a single block. This is done so programmatically by having a constant block height. As for the latter question, do you mean PoW (assuming you used miner)? There are various Sybil-resistance mechanisms.

2: Again, it depends on the protocol. For Bitcoin and Ethereum, no. There is a fixed block height, and as such there cannot be unordered dimensions for the blocks. No, once the block is mined, it cannot be modified. Therefore, a transaction cannot be added and as so the nonce will not change as well.

[aviorn36]

Thank you @krakxn , answer from othamie cleared my doubt. You second answer is some extra points, knowing partial filled blocked can be added depending upon protocol. You aware of some which I can look into?

[krakxn]

NEAR protocol is an example: involves sharding via subnets, each subnet/shard produces a chunk of the block. If the validators of a certain shard are absent, the shard is stalled and hence, the chunk which would have arose from it is not included in the block.