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We are developing an OS,But we can't proceed with normal C,we are in need of
basic interrupt routines,is it possible to use ROM BIOS functions,any alternatives please help us.

What do you mean, "normal" C? Can you still use C, just not stdio stdlib etc? If your compiler's 16-bit (eg. C--), then you should be able to use interrupts directly, otherwise you'll need DOS.H (which has int86() in my djgpp).

OSes weren't always the huge things that they are now. An os' job could almost be considered to provide a workin libc and task management. You might want to look into port or build libc.

If you really want to use ROM BIOS type stuff from within a PMode OS then you'll have to probably work on a virtual real mode process to do this. It's kinda like what DOS extenders do. You can find source to several free DOS extenders to see how they allow a process to run in PMode but still make BIOS calls.

-Chase