Ethereum is a blockchain-based computing platform and operating system whose core innovation is enabling smart contracts. Ethereum's smart contract functionality, and versatile scripting language, have made it the most popular network for creating decentralized applications. What makes Ethereum different from Bitcoin is that its primary purpose is to serve as a general purpose blockchain for creating DApps, and not as a payment network. Ethereum was created by Vitalik Buterin. It was launched in July 2015 and has become one of the most important blockchain platforms in the industry. Ether is the native currency of the Ethereum blockchain and can can be used as a transfer of value, as well as a form of compensation for mining. The Ethereum Virtual Machine (EVM) executes scripts using a network of public nodes. "Gas" is used as an internal transaction pricing mechanism that decides how resources are used on the network.

NEM is a cryptocurrency and blockchain platform that allows multiple ledgers on the same blockchain. NEM Smart Assets are used to create mosaics for any asset. Transaction fees are paid with NEM's native currency, XEM. NEM originally began as a community-oriented cryptocurrency that was built from the ground up in the Java programming language.
NEM's goal is to achieve widespread distribution through improved scale and speed. It pioneered several blockchain features such as its proof-of-importance (POI) consensus algorithm, encrypted messaging, a unique reputation system, and multi-signature accounts.
NEM is also developing a commercial blocckahin called Mijin, that is currently being tested by several companies and financial institutions.
In early 2018, approximately $400 million worth of XEM were stolen from a Japanese exchange called Coincheck, that was the victim of huge hack. The exchange failed to implement proper security for this coin protocol, and the hackers only stole XEM coins as a result. Instead of creating a fork to deal with this issue, NEM set up an automated tagging system that flagged these funds. NEM then stopped tracking these stolen coins

GAS is the token that is used to pay for transaction fees on the NEO network. The NEO platform uses two different tokens; GAS are used to fuel the network and give holders the right to use the NEO blockchain. Similar to Ether on the Ethereum network. Although it's possible to buy GAS on some exchanges, NEO token holders automatically generate GAS as the blockchain increases in size. 8 GAS are distributed for every 100 million NEO in circulation.

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