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ERC20 guarantees the token created to have simple transferability among wallets and contracts. ERC223 merges the token transfer function among wallets into one single function ‘transfer’. The biggest change is that ERC224 no longer allow token to be transferred to a contract that does not allow token withdrawal. The answer is ‘Transfer’ and ‘allow’ - a function that must exist in every ERC’20 contract. The answers are taken from a simple test of knowledge of the language used in smart contracts.
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