Hello Anoop P S,
One very important detail you need to look at is the voltage level needed for your micro-controller. Micro-controllers usually work with UART TTL 0-5V level, whereas your computer works with RS-232 -12 to 12V voltage levels. You will need a RS-232 Receiver/Transceiver to convert the voltage levels.
If you are already using a converter, I suggest trying to communicate through hyper terminal first, sending/receiving a single byte. Also make sure you disable flow control on your COM port, make sure you are using the same baud rate/data bits/start bits/stop bits.
O. Proulx
National Instruments
www.ni.com/support