Page 70 - DCAP404 _Object Oriented Programming

Unit 3: Review of Functions

return 0; Notes
}
int f(int length, int width, int height)
{
return (length * width * height);
}

3.5 Function Prototyping

Prototype of a function is the function without its body. The C++ compiler needs to about a
function before you call it, and you can let the compiler know about a function is two ways – by
defining it before you call it or by specifying the function prototypes before you call it. Many
programmers prefer a ‘Top-Down’ approach in which main() appears ahead the user-defined
function definition. In such approach, function access will precede function definition. To
overcome this, we use the function prototypes or we declare the function. Function-prototype
are usually written at the beginning of a program, ahead of any programmer-defined functions
including main(). In general, function prototype is written as:
Return-type name (type 1 arg. 1, type 2 arg. 2, ….. type n arg. n);
Where return-type represents the data type of the value returned by the function, name represents
the function name, type 1, type 2 …. type n represents the data-type of arguments art. 1, arg. 2 …
arg n. The function prototypes resemble first line to function definition, though it ends with the
semicolon. Within the function declaration, the names of arguments are optional but data-types
are necessary for eq. Int count (int);

The code snippet given below will cause compilation error because the main function does not
know about the called function one().
void main()

{
…
one(); //incorrect!! No function prototype available for one()
…
}
void one()
{
//function definition
}
To resolve this problem you should define the function before it is called as shown below:

void one()
{
//function definition
}
void main()

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