can anyone please suggest a real time clock ic that can be interfaced with a pic without using an RS232?

Answer 1

below is a link to maxim. they have several versions of RTC's. interfaces include, parallel, I2C, SPI, 3 wire.

I dont know of any that are interfaced through the RS232 port though. are you sure that is what you have?
Note: the parallel interface works just like external memory, and is probably the easiest to use.

Answer 2

I am currently building this microcontroller in EET 289, and was unable to locate the info in my book , for typical asynchronous communication speed hardware flow control is not required, but I can suggest going to www.freertos.org,they work with RTOS'S.