Structure of a program 2

Let us add an additional instruction to our first program:
// my second program in C++
#include <iostream>
using namespace std;
int main ()
{
cout << "Hello World! ";
cout << "I'm a C++ program";
return 0;
}
Hello World! I'm a C++ program
In this case, we performed two insertions into cout in two different statements. Once again, the separation in
different lines of code has been done just to give greater readability to the program, since main could have been perfectly valid defined this way:
int main () { cout << " Hello World! "; cout << " I'm a C++ program "; return 0; }
We were also free to divide the code into more lines if we considered it more convenient:
int main ()
{
cout <<
"Hello World!";
cout
<< "I'm a C++ program";
return 0;
}
And the result would again have been exactly the same as in the previous examples.
Preprocessor directives (those that begin by #) are out of this general rule since they are not statements. They are lines read and processed by the preprocessor and do not produce any code by themselves. Preprocessor directives must be specified in their own line and do not have to end with a semicolon (;).
Comments Comments are parts of the source code disregarded by the compiler. They simply do nothing. Their purpose is only to allow the programmer to insert notes or descriptions embedded within the source code.
C++ supports two ways to insert comments:
// line comment
/* block comment */
The first of them, known as line comment, discards everything from where the pair of slash signs (//) is found up to the end of that same line. The second one, known as block comment, discards everything between the /*
characters and the first appearance of the */ characters, with the possibility of including more than one line.
We are going to add comments to our second program:
/* my second program in C++
with more comments */
#include <iostream>
using namespace std;
int main ()
{
cout << "Hello World! "; // prints Hello
World!
cout << "I'm a C++ program"; // prints I'm a
C++ program
return 0;
}
Hello World! I'm a C++ program
If you include comments within the source code of your programs without using the comment characters
combinations //, /* or */, the compiler will take them as if they were C++ expressions, most likely causing one or several error messages when you compile it.