"Hello, world!"
And now, finally, the first
program:
//: C02:Hello.cpp
// Saying Hello with C++
#include <iostream> // Stream declarations
using namespace std;
int main() {
cout << "Hello, World! I am "
<< 8 << " Today!" << endl;
} ///:~
The cout object is handed a series
of arguments via the ‘<<’ operators. It prints out
these arguments in left-to-right order. The special iostream function
endl outputs the line and a newline. With iostreams, you can string
together a series of arguments like this, which makes the class easy to use.
In C, text inside double quotes is
traditionally called a “string.” However, the
Standard C++ library has a powerful class called string for manipulating
text, and so I shall use the more precise term character array for text
inside double quotes.
The compiler creates storage for
character arrays and stores the ASCII equivalent for each character in this
storage. The compiler automatically terminates this array of characters with an
extra piece of storage containing the value 0 to indicate the end of the
character array.
Inside a character array, you can insert
special characters by using escape sequences.
These consist of a backslash (\) followed by a special code. For example
\n means newline. Your compiler manual or local C
guide gives a complete set of escape sequences; others include \t
(tab), \\ (backslash), and
\b (backspace).
Notice that the statement can continue
over multiple lines, and that the entire statement terminates with a
semicolon
Character array arguments and constant
numbers are mixed together in the above cout statement. Because the
operator << is overloaded with a variety of
meanings when used with cout, you can send cout a variety of
different arguments and it will “figure out what to do with the
message.”
Throughout this book you’ll notice
that the first line of each file will be a comment that starts with the
characters that start a comment (typically //), followed by a colon, and
the last line of the listing will end with a comment followed by
‘/:~’. This is a technique I use to allow easy extraction of
information from code files (the program to do this can be found in volume two
of this book, at www.BruceEckel.com). The first line also has the name
and location of the file, so it can be referred to in text and in other files,
and so you can easily locate it in the source code for this book (which is
downloadable from
www.BruceEckel.com).
