use case diagram

bac2/os/chap3/Makefile

@@ -2,7 +2,10 @@
 CC = gcc
 CFLAGS = -g -Wall
 
-all: ex1 ex2 ex3 ex4 ex5
+all: ex1 ex2 ex3 ex4 ex5 ex6 ex7 group
+
+group: group.o mergeSort.o
+	$(CC) $(CFLAGS) -o $@ $+
 
 %.o: %.c
 	$(CC) $(CFLAGS) -c -o $@ $<
@@ -16,7 +19,7 @@ clean:
 mrproper: clean
 	rm -f ex1
 
-run: ex6
+run: group
 	./$<
 
 graph: run