The blockchain is the kind of Distributed Ledger.  

Blockchain data model is a chronological chain of digital blocks.  Each block includes a number of verified transactions.

The first block in Blockchain named Genesis Block.

Each block in a chain has a timestamp, reference to the preceding block in a chain and a hash signature that results from solving a cryptographical challenge termed “Proof Of Work”.

Timestamp, reference to the previous block and cryptographical signature ensure immutability of blockchain data model.  After new blocks have been appended to a blockchain it can not me be modified or deleted.

Genesis Block

Timestamp:

‘9999-12-31 23:59:59’

DATA

  1. Transaction 1
  2. Transaction 2
  3. Transaction 3

Proof Of Work

00000000F5B7E622FB973D9C60D45B00BBA6D7DF78DF3A39B19D3586EE02C80C85279F61DB80648743A7F0369…

Block

Timestamp:

‘9999-12-31 23:59:59’

DATA

  1. Transaction 3
  2. Transaction 4
  3. Transaction 5
Proof Of Work 00000000F5B7E622FB973D9C60D45B00…
Preceding Block Proof Of Work 00000000F5B7E622FB973D9C60D45B00…
Cryptography is performing a significant role in blockchain data structure implementation. Cryptography is a tool that applied to guarantee blockchain transactions immutability as well as forms a relationship among blocks in the blockchain.

F5B7E622FB973D9C60D45B00BBA6D7DF78DF3A39B19D3586EE02C80C85279F61DB80648743A7F036913C86C59EF1C7D69D13B3DB5D29A49DA327319FB337D3F1

A blockchain data structure support only write operations. New block appends to the ledger by referencing latest block hash (Proof of work). Blockchain decentralized architecture is designed to prevent a single party to be able to update transaction data in a block or delete blocks from a block chain.