diff --git a/03_day.pptx b/03_day.pptx
index c23f656..790262a 100644
Binary files a/03_day.pptx and b/03_day.pptx differ
diff --git a/03_day/sp/Android.bp b/03_day/sp/Android.bp
index 0e8bf69..5250796 100644
--- a/03_day/sp/Android.bp
+++ b/03_day/sp/Android.bp
@@ -1,7 +1,7 @@
 cc_binary {
-    name: "my_sp",
+    name: "my_wp",
     shared_libs: ["liblog", "libutils"],
     srcs: [
-        "sp_1.cpp",
+        "wp_1.cpp",
     ],
 }
diff --git a/03_day/sp/wp_1.cpp b/03_day/sp/wp_1.cpp
new file mode 100644
index 0000000..84e0156
--- /dev/null
+++ b/03_day/sp/wp_1.cpp
@@ -0,0 +1,119 @@
+#if 1
+#include <stdio.h>
+#include <utils/RefBase.h>
+#include <utils/StrongPointer.h>
+
+using namespace android;
+
+class AAA : public virtual RefBase
+{
+	int data;
+	public:
+		AAA(){ printf("AAA::AAA()\n"); }
+		~AAA() { printf("AAA::~AAA()\n"); }
+		void foo()   // void foo( AAA *this )
+		{ 
+			data = 10;  // this->data = 10; => (*0).data = 10;
+			printf("AAA::foo()\n"); 
+		}
+};
+
+int main()
+{
+	//((AAA*)0)->foo();  // AAA::foo(0);
+	{
+		wp<AAA> p1 = new AAA;
+		{
+			sp<AAA> p2 = p1.promote();
+			p2->foo();
+		}
+		printf("step 1.\n");
+		if( p1.promote() != 0 )
+			p1.promote()->foo();
+		else
+			printf("객체는 이미 소멸됨\n");
+	}
+	printf("step 2.\n");
+	return 0;
+}
+#endif
+
+#if 0
+#include <stdio.h>
+#include <utils/RefBase.h>
+#include <utils/StrongPointer.h>
+
+using namespace android;
+
+class AAA : public virtual RefBase
+{
+	public:
+		AAA(){ printf("AAA::AAA()\n"); }
+		~AAA() { printf("AAA::~AAA()\n"); }
+		void foo() { printf("AAA::foo()\n"); }
+};
+
+int main()
+{
+	{
+		wp<AAA> p1 = new AAA;
+		sp<AAA> p2 = p1.promote();
+		p2->foo();
+	}
+	return 0;
+}
+#endif
+#if 0
+#include <stdio.h>
+#include <utils/RefBase.h>
+#include <utils/StrongPointer.h>
+
+using namespace android;
+
+class AAA : public virtual RefBase
+{
+	public:
+		AAA(){ printf("AAA::AAA()\n"); }
+		~AAA() { printf("AAA::~AAA()\n"); }
+		void foo() { printf("AAA::foo()\n"); }
+};
+
+int main()
+{
+	{
+		sp<AAA> p1 = new AAA;
+		wp<AAA> p2 = p1;
+		p1->foo();
+	}
+	return 0;
+}
+#endif
+
+
+#if 0
+#include <stdio.h>
+#include <utils/RefBase.h>
+#include <utils/StrongPointer.h>
+
+using namespace android;
+
+class AAA : public virtual RefBase
+{
+	public:
+		AAA(){ printf("AAA::AAA()\n"); }
+		~AAA() { printf("AAA::~AAA()\n"); }
+		void foo() { printf("AAA::foo()\n"); }
+};
+
+int main()
+{
+	{
+		wp<AAA> pa = new AAA;
+		pa.promote()->foo();
+	}
+	return 0;
+}
+#endif
+
+
+