A Beginner's C++ Program

Sample program

#include <iostream>
using namespace std;
   
int main()
{
   cout <<  "Enjoy yourself with C++!"  << endl;
   return 0;
}

A C++ program is made up of objects with their accompanying member functions and global functions, which do not belong to any single particular class. Each function fulfills its own particular task and can also call other functions. You can create functions yourself or use ready-made functions from the standard library. You will always need to write the global function main() yourself since it has a special role to play; in fact it is the main program.

The short programming example on the opposite page demonstrates two of the most important elements of a C++ program. The program contains only the function main() and displays a message.

The first line begins with the number symbol, #, which indicates that the line is intended for the preprocessor. The preprocessor is just one step in the first translation phase and no object code is created at this time. You can type

#include <filename>

to have the preprocessor copy the quoted file to this position in the source code. This allows the program access to all the information contained in the header file. The header file iostream comprises conventions for input and output streams. The word stream indicates that the information involved will be treated as a flow of data.

Predefined names in C++ are to be found in the std (standard) namespace. The using directive allows direct access to the names of the std namespace.

Program execution begins with the first instruction in function main(), and this is why each C++ program must have a main function. The structure of the function is shown on the opposite page. Apart from the fact that the name cannot be changed, this function's structure is not different from that of any other C++ function.

In our example the function main() contains two statements. The first statement

cout << "Enjoy yourself with C++!" << endl;

outputs the text string Enjoy yourself with C++! on the screen. The name cout (console output) designates an object responsible for output.

The two less-than symbols, <<, indicate that characters are being "pushed" to the output stream. Finally endl (end of line) causes a line feed. The statement

return 0;

terminates the function main() and also the program, returning a value of 0 as an exit code to the calling program. It is standard practice to use the exit code 0 to indicate that a program has terminated correctly.

Note that statements are followed by a semicolon. By the way, the shortest statement comprises only a semicolon and does nothing.

A Beginner's C++ Program