The Fallback function:

can contain as much logic as you want, but it's better to keep it short and not exceed the gas stipend of 2300 gas.

cannot receive Ether, not even by adding the payable modifier.

can be used to avoid receiving ether.

To Iterate through a mapping, you:

you need an external helper variable.

can use the length parameter of the mapping.

you cannot iterate any mapping to make the overall language design more safe.

Solidity gets compiled:

to bytecodes which are essentially opcodes running instruction by instruction.

to bytecode that can't be understood by humans.

When considering smart contracts and the blockchain it's good:

to move only those parts to the blockchain that really need the blockchain. This way smart contracts can be easier to read, easier to test and are not so complex.

to move all existing logic to the blockchain, so everything runs on the same system. This way it might be more complex, but easier to maintain.

to move those parts to the blockchain that deal with Ether transfers. All other parts can remain in traditional database systems. This way only the value-transfer is on the blockchain.

A version pragma is a great way to make it clear:

for which compiler version a smart contract was developed for. It helps to avoid breaking changes.

for which blockchain a smart contract was developed for. It helps to avoid confusion with beta-customers.

for which blockchain node a smart contract was developed for. It helps to avoid mixing up different versions of go-ethereum.

Free Blockchain CBDE Exam Practice Questions & Explanations

Last updated on: Oct 14, 2026
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