Lecture 2: Introduction to smart-contracts
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What are smart-contracts?
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Smart contracts are scripts (think of a program / software) that are deployed and executed on the 
blockchain. 

Why do we need smart contracts? Without smart contracts, most blockchains can only be used to send 
tokens between two accounts. Smart contracts add another layer of possibilities by enabling 
arbitrary computation. For instance, one could develop a smart contract to add conditions for a transfer
to happen.