Smart contracts deployed on a blockchain have immutable code, meaning that once they are deployed, their code cannot be altered or modified. This is a key feature of blockchain technology and provides several benefits:

1. *Tamper-proof*: The code is unable to be tampered with, ensuring that the smart contract executes as intended.

2. *Transparency*: The code is publicly visible, allowing anyone to verify its functionality.

3. *Security*: The immutability of the code ensures that smart contracts are secure and resistant to manipulation.

4. *Trustless*: The immutability of the code eliminates the need for trust in a central authority, as the code executes autonomously.

5. *Predictable behavior*: The code's immutability ensures that smart contracts will execute predictably, without unexpected changes or modifications.

The immutability of smart contract code is a fundamental aspect of blockchain technology and provides a foundation for building secure, transparent, and trustless applications.