Intelligent interactive contract

When the contract needs to interact with other contracts on the block chain and when:

　　You need to define an interface (Interface)

　　　definition:

　　　　contract Number{

　　　　　　function getNum(address _myAddress) public view returns (uint);

　　　　}

　　　　While here, it looked like a contract and defined inside a function, however:

　　　　　　Function did not begin, but the use of a semicolon immediate end, which is the definition of some of the features interface interface.