How can we set the value in IBnCR?

What is the difference between WrPortI(IB0CR,&IB0CRShadow,0x0A) and
WrPortI(IB0CR,&IB0CRShadow,0xC8).How do we assign values 0X0A and OxC8 ?

You can find out what setting different bits in a register means by reading the processor manual. Go to the main DIGI website and look up the particular user manual for the board you are using.

For the Rabbit 4000 see

Chapter 24 has a complete description of the external IO control.