Header Files In C#, C++, VB

 

 Using Header Files

Header files are text files containing declarations and macros. By using an #include directive these declarations and macros can be made available to any other source file, even in other header files.

Pay attention to the following points when using header files:

• header files should generally be included at the start of a program before any other declarations
• you can only name one header file per #include directive
• the file name must be enclosed in angled brackets < ... > or double quotes " ... ".

Searching for Header Files

The header files that accompany your compiler will tend to be stored in a folder of their own—normally called include. If the name of the header file is enclosed by angled brackets < ... >, it is common to search for header files in the include folder only. The current directory is not searched to increase the speed when searching for header files.

C++ programmers commonly write their own header files and store them in the current project folder. To enable the compiler to find these header files, the #include directive must state the name of the header files in double quotes.

Example:

#include "project.h" 

The compiler will then also search the current folder. The file suffix .h is normally used for user-defined header files.

Standard Class Definitions

In addition to standard function prototypes, the header files also contain standard class definitions. When a header file is included, the classes defined and any objects declared in the file are available to the program.

Example:

#include <iostream>
using namespace std; 

Following these directives, the classes istream and ostream can be used with the cin and cout streams. cin is an object of the istream class and cout an object of the ostream class.