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# System prepended metadata

title: Blockchain course 4/27

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# Blockchain course 4/27

sally 

## transation

1. money transation
2. smart contract transation

## EVM

## Decentrialize App

## components of ethereum

## Account of ETH

1. External owned account
2. Contract account

## patricia tree 

## mnemonic phrases

account 不好記，所以用12個助憶詞較方便記

## target block time

## Solidity programming language

only int, no float

no overflow protection