Generate static libraries from liba & libb

c/Makefile

@@ -6,8 +6,12 @@
 #
 # Makefile $@:  The file name of the target of the rule
 # Makefile $^:  The names of all the prerequisites
+#
+# ar -c:        Create the archive
+# ar -r:        Update existing files in an archive
+# ar -s:        Add or update an archive index
 
-main: main.c liba.o libb.o
+main: main.c liba.a libb.a
 	gcc -g -Wall -o $@ $^ -lm
 
 liba.o: liba.c
@@ -16,5 +20,11 @@ liba.o: liba.c
 libb.o: libb.c
 	gcc -g -Wall -c -o $@ $^
 
+liba.a: liba.o
+	ar -csr $@ $^
+
+libb.a: libb.o
+	ar -csr $@ $^
+
 clean:
-	rm -rf *.o main
+	rm -rf *.o *.a main