#include <sys/stat.h>
#include <memory.h>
#include <fcntl.h>
#include <stdio.h>
#include <io.h>

struct mystruct {
    int i;
    char buf[5];
    double d;
};

int main(int argc, char* argv[])
{
        int fh = _open("file.dat",_O_RDWR | _O_BINARY);
  
          if (fh == -1)
          {   
               fh = _creat("file.dat",_S_IREAD | _S_IWRITE);

                if (fh == -1)
              
                      return 1;
           } 

    mystruct ms;
    memset(&ms,0,sizeof ms);
    ms.i = 43690;
    ms.d = 234881023;
    ms.buf = "Бука";

        _lseek(fh,0,SEEK_END);

        _write(fh,&ms,sizeof ms);

        _lseek(fh,0,SEEK_END);

        _read(fh,&ms,sizeof ms);

    return 0;
}