Functions in Solidity are modules of code that are associated with a contract. Functions are declared with a name, optional parameters, access modifier, optional constant keyword, and optional return type. This is shown in the following example:
function orderMatcher (uint x) private constant returns(bool return value)
In the preceding example, function is the keyword used to declare the function. orderMatcher is the function name, uint x is an optional parameter, private is the access modifier or specifier that controls access to the function from external contracts, constant is an optional keyword used to specify that this function does not change anything in the contract but is used only to retrieve values from the contract ...
