diff --git a/array/main.go b/array/main.go
new file mode 100644
index 0000000..3e4bc76
--- /dev/null
+++ b/array/main.go
@@ -0,0 +1,7 @@
+package main
+
+// Array is fixed length, also data stored in a
+
+func main() {
+
+}
diff --git a/benchmark/main.go b/benchmark/main.go
new file mode 100644
index 0000000..ac1fd6e
--- /dev/null
+++ b/benchmark/main.go
@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+type Human interface {
+	Speak()
+}
+
+type Australia struct {
+}
+
+func (h *Australia) Speak() {
+	fmt.Println("I am Australia")
+}
+
+func InterfacePresentation(vs ...interface{}) {
+	t := time.Now()
+	for _, v := range vs {
+		b := time.Since(t)
+		fmt.Println("Before Checking", b)
+		m, ok := interface{}(v).(Human)
+		a := time.Since(t)
+		fmt.Println("After Checking", a)
+		if ok {
+			m.Speak()
+		}
+	}
+
+}
+
+func Presentation(human ...Human) {
+	for _, h := range human {
+		h.Speak()
+	}
+}
+
+func main() {
+	var persons []interface{} = make([]interface{}, 100)
+	for i := 0; i <= 100; i++ {
+		persons = append(persons, &Australia{})
+	}
+	InterfacePresentation(persons...)
+}
diff --git a/shadow/main.go b/shadow/main.go
new file mode 100644
index 0000000..2812fac
--- /dev/null
+++ b/shadow/main.go
@@ -0,0 +1,21 @@
+package main
+
+import "fmt"
+
+func f() string {
+	return "test"
+}
+
+func init() {
+	fmt.Println(f())
+}
+
+var g = "g"
+
+func main() {
+	s := "hello world"
+	p := &s
+	*p = "H2"
+	fmt.Println(s, s[0], len([]byte(s)))
+
+}