smart contract written in Solidity, the programming language used for Ethereum:

This contract defines an owner variable and a value variable. The constructor is called when the contract is created and sets owner to be the address of whoever created the contract, ie msg.sender. The initial value of value is 0. The setValue function can be called by anyone and sets the new value for value. However, this function includes a require check that verifies that the person calling the function is the owner. If it is not, then the function will be rejected and value will not be changed.