> Hi, 
>  I am trying to port OCaml to a custom operating system which is tailored
> to my needs. I wish to know what things to be taken care of. I would be
> specifically interested to know which parts of the code I may be required
> to modify? 
>   What are the interfaces OCaml uses to talk with the OS ?

The core runtime system uses essentially ANSI C plus a little bit of POSIX
(file descriptors, open/read/write/lseek/close).  In particular, all
memory is allocated using malloc().

Some of the external libraries are more OS-dependent.  For instance,
the "Unix" library relies heavily on POSIX, although a partial port to
Win32 is also available.

If you have more specific questions, feel free to ask us (caml@inria.fr)
directly.

- Xavier Leroy