diff --git a/ex8.3/Shape.hh b/ex8.3/Shape.hh
new file mode 100644
index 0000000..fc8f92d
--- /dev/null
+++ b/ex8.3/Shape.hh
@@ -0,0 +1,16 @@
+#ifndef SHAPE_HH
+#define SHAPE_HH
+
+class Shape {
+public:
+
+  // Constructor, destructor
+  Shape() {} ;
+  virtual ~Shape() {} ;
+
+  // Pure virtual interface functions
+  virtual double surface() const = 0 ;
+  virtual double circumference() const = 0 ;
+} ;
+
+#endif
diff --git a/ex8.3/Square.hh b/ex8.3/Square.hh
new file mode 100644
index 0000000..fda5e54
--- /dev/null
+++ b/ex8.3/Square.hh
@@ -0,0 +1,23 @@
+#ifndef SQUARE_HH
+#define SQUARE_HH
+
+#include "Shape.hh"
+
+class Square: public Shape {
+public:
+
+  // Constructor, destructor
+  Square(double size) : _size(size) {} ;
+  virtual ~Square() {} ;
+
+  // Implementation of abstract interface
+  virtual double surface() const { return _size * _size ; }
+  virtual double circumference() const { return 4 * _size ; }
+
+private:
+
+  double _size ;
+
+} ;
+
+#endif