First Program

First program is C++

When the above program is compiled, linked and executed, the following output is displayed on the VDU screen.

Hello World!

Various components of this program are discussed below:

Comments

First three lines of the above program are comments and are ignored by the compiler. Comments are included in a program to make it more readable. If a comment is short and can be accommodated in a single line, then it is started with double slash sequence in the first line of the program. However, if there are multiple lines in a comment, it is enclosed between the two symbols /* and */

#include <iostream>

The line in the above program that start with # symbol are called directives and are instructions to the compiler. The word include with '#' tells the compiler to include the file iostream into the file of the above program. File iostream is a header file needed for input/ output requirements of the program. Therefore, this file has been included at the top of the program.

using namespace std;

All the elements of the standard C++ library are declared within std. This line is very frequent in C++ programs that use the standard library.

int main ( )

The word main is a function name. The brackets ( ) with main tells that main ( ) is a function. The word int before main ( ) indicates that integer value is being returned by the function main (). When program is loaded in the memory, the control is handed over to function main ( ) and it is the first function to be executed.

Curly bracket and body of the function main ( )

A C++ program starts with function called main(). The body of the function is enclosed between curly braces. The program statements are written within the brackets. Each statement must end by a semicolon, without which an error message in generated.

cout<<"Hello World!";

This statement prints our "Hello World!" message on the screen. cout understands that anything sent to it via the << operator should be printed on the screen.

return 0;

This is a new type of statement, called a return statement. When a program finishes running, it sends a value to the operating system. This particular return statement returns the value of 0 to the operating system, which means “everything went okay!”.

Printing Multiple Lines of Text with a Single Statement