ios - How to solve linker command failed with exit code 1 -

i getting below error when running in xcode 6.3. how solve error

ld: entry point (start) undefined.  in crt1.o architecture armv7 clang: error: linker command failed exit code 1 (use -v see invocation) 

check whether have stetted initial uiviewcontroller. if not select uiviewcontroller , set initial uiviewcontrollerr.