Formal parameters vs actual parameters

        1 Formal parameters ： Is the parameter named when defining a function or procedure . Generally speaking, it is a sign .2 The actual parameter ： It's during execution , When calling a function or procedure , Arguments passed to a function or procedure . Generally speaking, it is the actual value .3 Parameter , Is a variable , It changes with different users . for instance , I learned in middle school sin(x) function , there x It's a formal parameter , When you need to ask 1 When the sine value of , You will use it. sin(1), there 1 Is the actual parameter .4 The relationship between formal and actual parameters ： The two are combined at the time of call , Usually, the argument will pass the value to the formal parameter , After the formal parameter is removed, the function procedure operation is performed , Some values may then be returned to the caller via parameter or function symbols