added makefile

makefile.txt

@@ -0,0 +1,12 @@
+all: main arithmetic
+	g++ main.o arithmetic.o
+	
+main: main.cpp
+	g++ -c main.cpp
+
+arithmetic: arithmetic.cpp arithmetic.h
+	g++ -c arithmetic.cpp
+
+clean:
+	rm*.o
+	rm a.out