Where to Put Class Declarations and Method Definitions in C++

By: Ivan Lim Emailed: 1644 times Printed: 2112 times    

Latest comments
By: rohit kumar - how this program is work
By: Kirti - Hi..thx for the hadoop in
By: Spijker - I have altered the code a
By: ali mohammed - why we use the java in ne
By: ali mohammed - why we use the java in ne
By: mizhelle - when I exported the data
By: raul - no output as well, i'm ge
By: Rajesh - thanx very much...
By: Suindu De - Suppose we are executing

Each function that you declare for your class must have a definition. The definition is also called the function implementation. Like other functions, the definition of a class method has a function header and a function body.

The definition must be in a file that the compiler can find. Most C++ compilers want that file to end with .C or .CPP. This book uses .CPP, but check your compiler to see what it prefers.

 


NOTE: Many compilers assume that files ending with .C are C programs, and that C++ program files end with .CPP. You can use any extension, but .CPP will minimize confusion.

You are free to put the declaration in this file as well, but that is not good programming practice. The convention that most programmers adopt is to put the declaration into what is called a header file, usually with the same name but ending in .H, .HP, or .HPP. This book names the header files with .HPP, but check your compiler to see what it prefers.

For example, you put the declaration of the Cat class into a file named CAT.HPP, and you put the definition of the class methods into a file called CAT.CPP. You then attach the header file to the .CPP file by putting the following code at the top of CAT.CPP:

#include Cat.hpp

This tells the compiler to read CAT.HPP into the file, just as if you had typed in its contents at this point. Why bother separating them if you're just going to read them back in? Most of the time, clients of your class don't care about the implementation specifics. Reading the header file tells them everything they need to know; they can ignore the implementation files.

 


NOTE: The declaration of a class tells the compiler what the class is, what data it holds, and what functions it has. The declaration of the class is called its interface because it tells the user how to interact with the class. The interface is usually stored in an .HPP file, which is referred to as a header file. The function definition tells the compiler how the function works. The function definition is called the implementation of the class method, and it is kept in a .CPP file. The implementation details of the class are of concern only to the author of the class. Clients of the class--that is, the parts of the program that use the class--don't need to know, and don't care, how the functions are implemented.

C++ Home | All C++ Tutorials | Latest C++ Tutorials

Sponsored Links

If this tutorial doesn't answer your question, or you have a specific question, just ask an expert here. Post your question to get a direct answer.



Bookmark and Share

Comments(0)


Be the first one to add a comment

Your name (required):


Your email(required, will not be shown to the public):


Your sites URL (optional):


Your comments:



More Tutorials by Ivan Lim
Requesting a Signed Certificate from a Certification Authority example using keytool in Java
The if-then Statement in Java
SELECT Statements
The BodyTag Interface in JSP
Handling Duplicate Form Submissions in Struts
Standard Input and Output in C
A sample that shows Java Beans, Servlets and JSP working together
Recursion in C
Using Multibox in Struts
switch in C
Word Counting sample program in C
Java Bean Scopes in JSF
Using cout.width() in C++
Types of configurations in J2ME
How to get the CLDC and MIDP version from a J2ME program

More Tutorials in C++
Two-Dimensional Array Manipulation in C++
Calculate average using Two-Dimensional Array in C++
Compute the square root of the sum of the squares of an array in C++
Matrix using nested for loops in C++
Sorting an array of Strings in C++
Calculating total based on the given quantity and price in C++
Compiling and Linking Multiple Source Files in C++
Enumerations in C++
Program to add two numbers in C++
Comments in C++
while loop in C++
for loop in C++
Programming errors a compiler will detect in C++
if in C++
Using the Built-in Arithmetic Types in C++

More Latest News
Most Viewed Articles (in C++ )
Using Comments in a C++ Program
Using cout in C++
Using peek() and putback() with cin in C++
Calculating total based on the given quantity and price in C++
Demonstration of Prefix and Postfix operators in C++
Escape Sequences for Nonprintable Characters in C++
Demonstrating global and local variables in C++
C++ Recursion function explained using Fibonacci series
Where to Put Class Declarations and Method Definitions in C++
Classes with Other Classes as Member Data in C++
Nested Loops in C++
Dot (.) vs Arrow (->) to access data members in C++
Converting Pointers that Operate on Arrays in C++ to Java
Converting C++ Multiple-Inheritance Hierarchies to Java
ctime() sample program in C++
Most Emailed Articles (in C++)
Returning values from a function in C++
while (1) Loops in C++
Using Comments in a C++ Program
Public versus Private members in C++
The indirection operator (*) - dereference operator.
Calculate average using Two-Dimensional Array in C++
Compute the square root of the sum of the squares of an array in C++
Specifying default values to function parameters in C++
continue and break statements in C++
const Pointers in C++
Sorting an array of Strings in C++
Advanced if Statements in C++
while Loops in C++
Dot (.) vs Arrow (->) to access data members in C++
Stray or Dangling Pointers in C++