Standard library `FILE` type [duplicate]

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Possible Duplicate:

Why is FILE all-caps as in FILE*?

Why is the standard library FILE type written uppercase ?

Is it because of its opaque nature ?

Thank you.

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If you look at the naming convention used in C, upper case is typically used for preprocessor macros. My guess is that it originally was implemented as a macro expanding to the concrete type used by the library implementation.

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From here

"Strictly speaking, in C the FILE type is a library defined (in stdio.h header) type alias (see typedef keyword). No need to use FILE type as such, only FILE* (pointer to FILE) type. It's (one of;) C language funny idioms. As usually, FILE type alias denotes library defined structure, but don't use its members directly (it's implementation dependent entity)."

Also this:

typedef FILE *stream;

Finally here:

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It's not an opaque type, it's usually a C struct, but its fields are implementation defined.

I guess the uppercase is because history...

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Not sure, but note that there are only a few types declared in the standard C library. Probably the FILE was the very first defined, and the *_t style wasn't yet invented.

Or maybe in primitive C versions it was a macro... think what happened before they invented the typedef:

#define FILE struct __file

Instead of:

typedef struct __file FILE;