Introduction
Function prototypes are the declarations of functions used by programmers in a program. These declarations provide the compiler with specific information about the function such as the name, number and type of parameters passed to the function. Although function prototypes serve as a guideline for the compiler about the function, there are certain elements that function prototypes do not have to include and this guide will provide more insights regarding what exactly these elements are.
Body
Function prototypes are declarations that inform the compiler about the format or layout of the functions in a program. It provides the compiler with information regarding the parameters needed by the function and the order of these parameters. It also helps the compiler to recognize if the function includes a return type or not.
The formula for writing a function prototype is quite simple. It can be described as follows:
return_type function_name (par1, par2, par3, ..., parN);
The five elements that are essential for writing a function prototype are:
- return_type
- function_name
- parameters
However, there are a few other elements that may be included in a function prototype but are not necessary. These elements are
- permission declaration
- classname/struct name
- memory modifier
Permission declaration
This element is usually used for representing the scope of the function. The permission declaration can be public, private or protected. However, it is not imperative to include this element in the function prototype. It can be used when the context of the program or the project requires it.
Classname/Struct name
The classname or Struct name is included in the function prototype as part of its scope. It includes the function declaration in a structured programming environment such as C++.
The name of the structure or class may be added before the data type (return type) of the function if the function operates on objects of the class or structure. It is not mandatory to include this element in the function prototype but it may be necessary depending on the context of the problem.
Memory modifier
The memory modifier is an element that may be added to the function prototype that reflects the memory requirement for a function. This element is usually added for dynamic allocation of memory for a function. It can also be used for stack and heap allocation. The memory modifier can be static, register, auto, extern, as well as many other options. It is an optional element in a function prototype and is usually included depending on the memory requirement of the application.
FAQ
What is the order of elements to be included in a function prototype?
The order of elements that should be included in a function prototype follows the general formula return_type function_name (par1, par2, par3);. This includes the return type of the function, the name of the function, and the parameters passed to the function.
What is a permission declaration used for?
A permission declaration is element which defines the scope of a function. Depending on the context of the application, a permission declaration could be private, public, or protected.
Is it necessary to include a class/struct name for a function prototype?
No, it is not necessary to include a class or struct name for a function prototype. This is usually added only if the function operates on objects of the class or structure.
What memory modifiers can be used to modify a function prototype?
Memory modifiers that can be a part of the function prototype are static, register, auto, extern, and many more. The memory modifier is usually included in the function prototypes to reserve dynamic allocation for the function and to control stack and heap allocation.
Can permission declaration, class/struct names and memory modifiers be optional parts of a function prototype?
Yes, permission declaration, class/struct names, and memory modifiers can all be optional parts of a function prototype. Their usage may depend on the context of the application.
Conclusion
Function prototypes are the declarations of functions used to inform the compiler about the layout of the function. Although the minimal elements that are necessary to be included in a function prototype are the return type, function name, and the parameters passed, some other optional elements can also be included in a function prototype such as permission declaration, class/struct names and memory modifiers.
References
Wikipedia - " Function prototype": Retrieved from https://en.wikipedia.org/wiki/Function_prototype
Tutorialspoint - " Function prototype": Retrieved from https://www.tutorialspoint.com/cprogramming/c_function_declarations.htm