Constants and immutables in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a constant in blockchain programming?

A constant is a value that is set once and cannot be changed during the execution of a smart contract. It helps keep data safe and predictable.

beginner

What does 'immutable' mean in the context of blockchain variables?

Immutable means the variable can be assigned only once during contract creation and cannot be changed afterward, ensuring fixed data after deployment.

intermediate

Why use constants and immutables in smart contracts?

They save gas (transaction cost) and increase security by preventing accidental or malicious changes to important values.

intermediate

How do constants differ from immutables in blockchain code?

Constants are fixed at compile time and cannot be changed ever. Immutables are set once during contract deployment and then stay fixed.

beginner

Example: What happens if you try to change a constant value in a smart contract?

The code will not compile or will throw an error because constants cannot be modified after they are set.

Which of the following is true about constants in blockchain smart contracts?

A They are only used for temporary values.

B They can be changed anytime during contract execution.

C They are set during contract deployment and can be changed later.

D They are set once and cannot be changed ever.

Constants are fixed values set at compile time and cannot be changed.

What is the main difference between constants and immutables?

A Immutables can be changed anytime; constants cannot.

B Constants are cheaper to use than immutables.

C Constants are set at compile time; immutables are set once during deployment.

D There is no difference.

Constants are fixed at compile time, while immutables are assigned once during contract deployment.

Why do constants and immutables save gas in smart contracts?

A Because their values are stored in cheaper ways and not changed.

B Because they allow unlimited changes.

C Because they increase contract size.

D Because they require more computation.

Fixed values reduce storage and computation costs, saving gas.

When can an immutable variable be assigned a value?

A Only once during contract deployment.

B Multiple times during contract execution.

C Only after contract deployment.

D Never assigned a value.

Immutables are assigned once during deployment and then cannot be changed.

What happens if you try to modify a constant after deployment?

A The contract crashes at runtime.

B The contract will not compile or will throw an error.

C The contract ignores the change silently.

D The constant value changes successfully.

Constants cannot be modified; attempting to do so causes compile errors.

Explain the difference between constants and immutables in blockchain smart contracts.

Think about when each value is assigned and if it can change later.

Why is it important to use constants and immutables in smart contract development?

Consider how fixed values help protect your contract and save costs.