Online Resources for Preprocessor Directives

Does anyone know of a tutorial or a lesson on Preprocessor Directives?
I looked at MSDN Visual C++ refrence material but it is written in such a way that I barely understand it. I am looking for something that explains it in plain english!

Here is one: http://www.cplusplus.com/doc/tutorial/preprocessor.html

There really aren't many preprocessor directives. The ones you will most likely use are:

Code:

---

#define
#include
#ifdef
#else
#endif
#if
#pragma

---

Honestly, I never really used anything else but those.

How much explaining does #include, #define and #if take?

#define is quite complex - macro substitution has some strange rules.

There's also #error, which is very simple.

I've never used #line myself, but I've used tools which have (i.e. bison).

I've often used defined(), which isn't a preprocessor directive, but it is related. And what about #elif? :)

(Side question: are you supposed to put double-quotes around the text after a #error directive?)

(Side answer: no.)

defined() is a preprocessor keyword.

#if cond1
#elif cond2
#endif

==

#if cond1
#else
#if cond2
#endif
#endif

Some other preprocessors don't support #elif, by the way.

(Aside: thank you.)

As far as I know, #elif is ANSI standard . . . are you referring to other types of preprocessors, or what?

Old, old, old preprocessors. But they still exist in some unices.

I believe there is also #ifndef, #undef and the string-ify operation.

QuantumPete

Stringify, yes, and token concatenation.

Don't forget the Preprocessor variables too, like __LINE__ and such, if you want to learn about the Preprocessor capabilities. I used __LINE__ just the other day writing a return code checker macro when writing a C program that uses a lot of the new "xxxx_s" safe functions.