Preprocessor Directive

The preprocessor directive #include<iostream.h> involves all the statements of the header file iostream.h. It holds instructions and predefined constants which will be used in the program. It plays the similar role as in which of the stdio.h of C. The header file iostream.h holds declarations which are required by the cout and cin objects. There are a number of such preprocessor directives gives through the C++ library, and they have to be included depending on the built-in functions used in the program. Within effect, these directives are processed before any other executable statements in the source file of the program through the compiler.