How to make library generic?

ProgrammableLib/Makefile

@@ -0,0 +1,14 @@
+TARGET: exe
+libdll.a: dll.o
+	ar rs libdll.a dll.o
+dll.o: dll.c
+	gcc -c -I . dll.c -o dll.o
+exe: application.o libdll.a
+	gcc application.o -o exe -L . -ldll
+application.o: application.c
+	gcc -c -I . application.c -o application.o
+clean:
+	rm *.o
+	rm libdll.a
+	rm exe
+