X Windows Libraries Required

Hi,
I tried to compile a code referencing XWindows Programming Functions, i found out that i have no XWindows Header files present. But XWindows is running on my System.Is the XWindows Development package different from the XWindows running on my system? if so, can you instruct me how to obtain and install XWindows development libraries on my Unix (NCR MPRAS).

Thanks and Regards,

Pravin