How is ethereum different from bitcoin?
Ethereum’s purpose is not primarily to be a digital currency payment network.
While the digital currency ether is intended as a utility currency to pay for use of the Ethereum platform as the world computer.
Ethereum is designed to be a general-purpose programmable blockchain that runs a virtual machine capable of executing code of arbitrary and unbounded complexity.
Ethereum’s language is Turing complete, meaning that Ethereum can straightforwardly function as a general-purpose computer.
The Ethereum platform was designed to abstract detailed implementations of peer-to-peer networks, blockchains, consensus algorithms, etc… providing a deterministic and secure programming environment for decentralized blockchain applications.
While bitcoin keeps track of bitcoin’s ownership, ethereum tracks the state transition of a general-purpose data store, which is stored in key-value tuple.
Ethereum can load code into its state machine and run that code, storing the resulting state changes in its blockchain.
About Turing completeness
Note: Turing machine is a machine composed of memory, head, state and symbols. Head reads memory from left to right, performing jobs pre-determined by symbols, and overwrites the state in it’s position.
If a machine is Turing-complete, it means it can simulate any Turing machine.
Due to the fact that it can simulate any programs, Turing-complete machines can be stuck in infinite loops or computation that needs huge resoureces. And it is also proven that we cannot predict whether a program will end in finite time or not.
To solve this problem, Ethereum introduced the concept of gas. While running a smart contract, in each operations( computations, data access, etc. ), a pre-defined amount of gas is used. When sending transaction to trigger execution, a user has to set a gas limit. If a gas used in execution exceeds the gas limit, the EVM will terminate the execution, leaving the state unchanged.
This article is scrapped from “Mastering Ethereum”
