two different versions of the software until the incompatibilities are

fixed.

Soft fork

When the new branch of the blockchain is backward compatible, a

“soft fork” occurs, meaning that nodes can rely on data and logic from

the old branch when they process transactions on the new branch.

Hard fork

A software update that is not backward compatible is a “hard fork”.

So, any blocks coming after the activation of the software update will

have to follow the new rules in order to be considered valid.

J ourney of blockchain

The j ourney of blockchain from its inception to current times can be traced

as follows:

19 89 : Prof Yuj iIj iri (Triple Entry Accounting framework)

19 9 0: Adam Back (Developed Hashcash puzzles)

19 9 1: Stuart Haber and W. Scott Stornetta on How to Timestamp a

digital document.

19 9 2: Bayer, Haber, and Stornetta on How Merkle Trees are

incorporated into the design, which collects several documents into

one block, thereby improving its efficiency.

2002: David Maziè res and Dennis Shasha proposed a network file

system with decentralized trust.

2005: Nick Szabo proposed a blockchain—

like a system for

decentralized property titles, bit gold payment system utilizing

chained proof-of-work and timestamping.

2005: IAN GRIGG proposed triple entry accounting.

2008: The first blockchain was conceptualized by SatoshiNakamoto,

which serves as the public ledger for all transactions on the network.

The first digital currency, Bitcoin came into existence to solve the

double-spending problem without requiring a trusted authority through

the use of a blockchain.