Huzefa Khairullah:

This is your 3rd thread, the last one you did not particiate and you only posted your problem and left the thread. i hope this one is different...

I would first check connections for the keypad which pin are columns, and which one are rows

Grab a pencil and a sheet and do with drawings what your code must do in order to recognize the key, sometimes i do this when i'm not sure what i must do (i draw cycles, scanning sequence, etc)

then make a flow chart and implement it with comments, you can debug with RS232 and send to the computer the information you are proccesing if your code is not working properly

we can start helping you if you post your code and schematic as everybody told before

I hope you continue the thread
regards