To understand the concept of rs232 communication it is better to start with hyperterminal or any other terminal program.
Connect your device to the rs232 port of your computer. if your computer doesn't have a rs232 port. then you can use a usb to rs232 converter to use it via usb.
then start hyperterminal program in windows xp.
You can start it from start > programs > accessories > communications > hyperterminal.
it will ask you for basic settings such as name, port, etc
fill them and proceed
then in the properties you have to change the setting according to your device specification. most of the devices came with a default baud rate 9600bps. if your device is different then change the baud rate, parity, stop bit, etc according to the device manual.
then connect to the device by clicking connect button.
click the capture text from transfer menu and then give it a file name such as kathirblog.txt
then your device sends data to hyperterminal and displayed in the area. you can save it.
or you can communicate with the device by sending a file or receiving a file using the transfer menu