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Concept
Function prototype
Summary
In computer programming, a function prototype or function interface is a declaration of a function that specifies the function’s name and type signature (arity, data types of parameters, and return type), but omits the function body. While a function definition specifies how the function does what it does (the "implementation"), a function prototype merely specifies its interface, i.e. what data types go in and come out of it. The term "function prototype" is particularly used in the context of the programming languages C and C++ where placing forward declarations of functions in s allows for splitting a program into translation units, i.e. into parts that a compiler can separately translate into s, to be combined by a linker into an executable or a library. The function declaration precedes the function definition, giving details of name, return type, and storage class along with other relevant attributes.
Function prototypes can be used when either:
Defining an ExternalType
Creating an Interface part
In a prototype, parameter names are optional (and in C/C++ have function prototype scope, meaning their scope ends at the end of the prototype), however, the type is necessary along with all modifiers (e.g. if it is a pointer or a reference to parameter) except alone.
In object-oriented programming, interfaces and abstract methods serve much the same purpose.
Consider the following function prototype:
void Sum( int a, int b );
OR
void Sum( int, int );
OR
auto Sum( int, int ) -> void; // C++ only
Function prototypes include the function signature, the name of the function, return type and access specifier. In this case the name of the function is "Sum". The function signature defines the number of parameters and their types. The return type is "void". This means that the function is not going to return any value. Note that the parameter names in the first example are optional.
In early versions of C, if a function was not previously declared and its name occurred in an expression followed by a left parenthesis, it was implicitly declared as a function that returns an int and nothing was assumed about its arguments.
Official source
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Ontological neighbourhood
Related courses (2)
CS-119(c): Information, Computation, Communication
L'objectif de ce cours est d'introduire les étudiants à la pensée algorithmique, de les familiariser avec les fondamentaux de l'Informatique et de développer une première compétence en programmation (
CS-119(a): Information, Computation, Communication
D'une part, le cours aborde: (1) la notion d'algorithme et de représentation de l'information, (2) l'échantillonnage d'un signal et la compression de données et (3) des aspects
liés aux systèmes: ordi
Related concepts (10)
Const (computer programming)
In some programming languages, const is a type qualifier (a keyword applied to a data type) that indicates that the data is read-only. While this can be used to declare constants, in the C family of languages differs from similar constructs in other languages in being part of the type, and thus has complicated behavior when combined with pointers, references, composite data types, and type-checking. In other languages, the data is not in a single memory location, but copied at compile time on each use.
Include directive
Many programming languages and other computer files have a directive, often called include, import, or copy, that causes the contents of the specified file to be inserted into the original file. These included files are called s or copybooks. They are often used to define the physical layout of program data, pieces of procedural code, and/or forward declarations while promoting encapsulation and the reuse of code or data. In computer programming, a header file is a file that allows programmers to separate certain elements of a program's source code into reusable files.
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