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Assign an identifier, name, to a function; Define formal parameters with a name and data type for each; Assign a data type to the return value, if any; Specify a return value in the function body; Call a function; Provide actual parameters that correspond to a called function's formal parameters; Return control to the caller at the point of call
C# (/ ˌ s iː ˈ ʃ ɑːr p / see SHARP) [b] is a general-purpose high-level programming language supporting multiple paradigms.C# encompasses static typing, [16]: 4 strong typing, lexically scoped, imperative, declarative, functional, generic, [16]: 22 object-oriented (class-based), and component-oriented programming disciplines.
A function call using named parameters differs from a regular function call in that the arguments are passed by associating each one with a parameter name, instead of providing an ordered list of arguments. For example, consider this Java or C# method call that doesn't use named parameters:
The return value from a function is provided within the function by making an assignment to an identifier with the same name as the function. [5] However, some versions of Pascal provide a special function Exit(exp); that can be used to return a value immediately from a function, or, without parameters, to return immediately from a procedure. [6]
Notably, the delivery need not be made by the clerk who took the order. A callback need not be called by the function that accepted the callback as a parameter. Also, the delivery need not be made directly to the customer. A callback need not be to the calling function. In fact, a function would generally not pass itself as a callback.
In case of call by value, what is passed to the function is the value of the argument – for example, f(2) and a = 2; f(a) are equivalent calls – while in call by reference, with a variable as argument, what is passed is a reference to that variable - even though the syntax for the function call could stay the same. [5]
Each time a function is called in a program, a block of memory called an activation record is allocated on top of the call stack. Generally, the activation record stores the function's arguments and local variables. What exactly it contains and how it's laid out is determined by the calling convention.
When a function has to tail-call another, instead of calling it directly and then returning the result, it returns the address of the function to be called and the call parameters back to the trampoline (from which it was called itself), and the trampoline takes care of calling this function next with the specified parameters.