Any one know how my program should be like when i need to pass in information for example "a" and display it in a display box... through serial communication.
MSDN has examples of serial communication programming on a Win32 platform. There are hundreds upon hundreds of Win32 programming websites on the internet, however Keil's Discussion Forum is not among them. My Usenet news server lists 2111 Microsoft-related newsgroups. Given all of that, I think your time would be much better spent inquiring about PC-related topics on PC-related venues, and not here, but that's just my opinion.