ex3.o: In function `main':
/in/ex3.cpp:37: undefined reference to `encrypt_c()'
/in/ex3.cpp:41: undefined reference to `decrypt_c()'
/in/ex3.cpp:52: undefined reference to `encrypt_s()'
/in/ex3.cpp:56: undefined reference to `decrypt_s()'
collect2: error: ld returned 1 exit status
/in/compile/Makefile:17: recipe for target 'ex3' failed
make: *** [ex3] Error 1