Re: Unclear in Macros by Bruce
Bruce
Thu Nov 18 06:56:04 CST 2004
Just the underscores. Underscores are just characters. So what is unclear?
Macros are macros, they are just a way to replace a token with one or more
other tokens in the preprocessor.
But:
> eg: #ifdef _CEDDK_ is just defined in that file, it could be anything
but the author chose that.
> #ifdef __cplusplus is defined by the compiler and may not be part of a
standard, I don't know, it is just a macro.
__FILE__ was defined by K&R.
--
Bruce Eitman (eMVP)
Senior Engineer
beitman AT applieddata DOT net
Applied Data Systems
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"Manoj" <Manoj@discussions.microsoft.com> wrote in message
news:DDADEE71-8015-4492-AE5A-125CE812C7E5@microsoft.com...
> hai,
> recently i came to know that macros are 2 types
> 1) starting with single underscore
> 2) starting with double underscore and starting & ending with double
> underscore
> eg: #ifdef _CEDDK_
> #define _CEDDK_
> #endif
>
> #ifdef __cplusplus
> extern "C"
> #endif
> similary __FILE__ is there in c compilers..
>
> can u pls explain what is the difference between these double and
single
> underscores,with the above examples....
>
> Experts pls help me
>
>
> Thanking You
>