i want to know the whole concept of file

Good god, can't you come up with something a little more specific?

Here's all of it...

#ifndef _FILE_DEFINED
struct _iobuf {
        char *_ptr;
        int   _cnt;
        char *_base;
        int   _flag;
        int   _file;
        int   _charbuf;
        int   _bufsiz;
        char *_tmpfname;
        };
typedef struct _iobuf FILE;
#define _FILE_DEFINED
#endif

>Here's all of it...
Wrong. First, you assumed too much about the question. Second, you assume that the structure you posted is universal. Third, you didn't explain squat about it. Someone who doesn't understand how stdio works internally isn't going to suddenly become enlightened simply by seeing the members of FILE. I had to actually implement the damn thing to get a good feel of the "whole concept".

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