State variables in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a state variable in blockchain smart contracts?

A state variable is a variable whose value is permanently stored on the blockchain. It keeps data between function calls and transactions.

beginner

Where are state variables stored in a blockchain smart contract?

State variables are stored in the contract's storage on the blockchain, making their values persistent and shared across all users.

beginner

How do state variables differ from local variables in smart contracts?

State variables are stored permanently on the blockchain, while local variables exist only temporarily during function execution and are not saved.

intermediate

Why should you be careful when updating state variables in smart contracts?

Updating state variables costs gas (transaction fees) because it changes blockchain storage. Minimizing updates saves cost and improves efficiency.

beginner

Give an example of declaring a state variable in Solidity.

Example:

uint public count;

This declares a state variable named count of type unsigned integer, stored on the blockchain.

What happens to a state variable's value after a smart contract function finishes execution?

A It is saved permanently on the blockchain.

B It is deleted immediately.

C It resets to zero.

D It becomes a local variable.

State variables keep their values permanently on the blockchain after function execution.

Which of these variables is stored temporarily during function execution?

A State variable

B Local variable

C Global variable

D Constant variable

Local variables exist only during function execution and are not saved on the blockchain.

Why does updating a state variable cost gas in Ethereum?

A Because it changes the blockchain storage.

B Because it sends tokens.

C Because it calls another contract.

D Because it reads data.

Changing state variables modifies blockchain storage, which requires gas fees.

Which keyword is used to declare a state variable in Solidity?

A uint

B storage

C memory

D public

The visibility keyword like public is used with the type to declare a state variable accessible outside the contract.

Where are state variables stored?

A In temporary memory during execution

B In the user's local machine

C In the contract's storage on the blockchain

D In the transaction logs only

State variables are stored in the contract's persistent storage on the blockchain.

Explain what state variables are and why they are important in blockchain smart contracts.

Think about how data stays saved between transactions.

Describe the difference between state variables and local variables in smart contracts.

Consider where each variable lives and how long it lasts.