I developed a program in OSX 10.6 SDK. And deployed to OsX 10.5. it did not work. So, I changed base SDK to 10.5 in XCode but many sources were not compiled, made many errors. For examples , NSApplicationDelegate protocol does not exists. And methods of NSPasteboard are different from 10.6. Do I have to change these sources according to 10.5 Spec? Is there anyway that one source covers both 10.5 and 10.6 ?