Programming and Graphics

100 Introduction to C++ Programming and Graphics

#include<file> fileis a system header file provided with the compiler

#include ”file” fileis either a user-defined header file

or a system header file

Table 4.4.1Syntax of theincludedirective system and user-defined header files.
The current directory is searched first for a user-defined header file.

4.4 Functions in individual files and header files............

Medium-size and large codes are split into a number of source files hosting the
main program and various functions. Each file is compiled independently to
produce the corresponding object file, and the object files are linked to build
the executable. In C++, each file containing user-defined functions must be
accompanied by aheader filethat declares these functions.

As an example, consider a code that has been split into two files. The
first file namedgreetingsdr.cccontains the following main program:

#include "greetings.h"

using namespace std;

int main()

{

greetings();

return 0;

}

The second file namedgreetings.cccontains the following user-defined
function:

#include<iostream>

using namespace std;

void greetings()

{

cout << "Greetings\n";

}

The first line of the main program is a compiler preprocessor directive
requesting the attachment of the header filegreetings.h. The significance of the
double quotes in the syntax#include "greetings.h"is illustrated in Table
4.4.1.