Solidity Solidity Data Types and Storage 3

Question 1

What is the primary advantage of using calldata over memory for external function parameters in Solidity?

Accepted Answer

calldata is read-only and avoids an extra copy, making it more gas-efficient

Answer

calldata is the raw, read-only transaction input and avoids copying data into memory, making it the most gas-efficient location for external function parameters that are not modified.

Question 2

How many EVM storage slots does a single uint256 state variable occupy?

Accepted Answer

1 slot

Answer

A uint256 is 32 bytes (256 bits), which fits exactly into one 32-byte EVM storage slot.

Question 3

Which combination of variables can be packed together into a single 32-byte EVM storage slot?

Accepted Answer

A uint128 and a uint128

Answer

Two uint128 variables each occupy 16 bytes, and together they sum to exactly 32 bytes — one full storage slot.

Question 4

What happens when you assign a storage struct to a local variable without the 'memory' keyword in Solidity?

Accepted Answer

A storage pointer (reference) to the original is created

Answer

Assigning a storage struct to a local variable without 'memory' creates a storage reference, so changes to the local variable also modify the original state variable.

Question 5

What storage slot number is assigned to the first state variable declared in a Solidity contract?

Accepted Answer

Slot 0

Answer

Solidity assigns storage slots sequentially starting at slot 0, so the first declared state variable occupies slot 0.

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Solidity Solidity Data Types and Storage 3