diff --git a/io/kotlinstudy/tour/Practice.kt b/io/kotlinstudy/tour/Practice.kt
new file mode 100644
index 0000000..8c21ec9
--- /dev/null
+++ b/io/kotlinstudy/tour/Practice.kt
@@ -0,0 +1,7 @@
+package io.kotlinstudy.tour
+
+fun main() {
+    val name = "Mary"
+    val age = 20
+    println("$name is $age years old")
+}
\ No newline at end of file
diff --git a/io/kotlinstudy/types/BasicTypes.kt b/io/kotlinstudy/types/BasicTypes.kt
new file mode 100644
index 0000000..0d8ce42
--- /dev/null
+++ b/io/kotlinstudy/types/BasicTypes.kt
@@ -0,0 +1,18 @@
+package io.kotlinstudy.types
+
+fun main() {
+    var customers = 10
+
+    customers = 8
+    println("There are $customers customers")
+    customers = customers + 3
+    println("There are $customers customers")
+    customers += 7
+    println("There are $customers customers")
+    customers -= 3
+    println("There are $customers customers")
+    customers *= 2
+    println("There are $customers customers")
+    customers /= 3
+    println("There are $customers customers")
+}
\ No newline at end of file
diff --git a/io/kotlinstudy/types/Declare.kt b/io/kotlinstudy/types/Declare.kt
new file mode 100644
index 0000000..f497358
--- /dev/null
+++ b/io/kotlinstudy/types/Declare.kt
@@ -0,0 +1,16 @@
+package io.kotlinstudy.types
+
+fun main() {
+    val a: Int = 1000
+    println(a)
+    val b: String = "log message"
+    println(b)
+    val c: Double = 3.14
+    println(c)
+    val d: Long = 100_000_000_000_000
+    println(d)
+    val e: Boolean = false
+    println(e)
+    val f: Char = '\n'
+    println(f)
+}
\ No newline at end of file
diff --git a/io/kotlinstudy/types/Error.kt b/io/kotlinstudy/types/Error.kt
new file mode 100644
index 0000000..74e261a
--- /dev/null
+++ b/io/kotlinstudy/types/Error.kt
@@ -0,0 +1,7 @@
+package io.kotlinstudy.types
+
+fun main() {
+    val d: Int
+//    println(d)
+
+}
\ No newline at end of file
diff --git a/io/kotlinstudy/types/SpecifyType.kt b/io/kotlinstudy/types/SpecifyType.kt
new file mode 100644
index 0000000..d733066
--- /dev/null
+++ b/io/kotlinstudy/types/SpecifyType.kt
@@ -0,0 +1,9 @@
+package io.kotlinstudy.types
+
+fun main() {
+    val d: Int
+    d = 3
+    val e: String = "hello"
+    println(d)
+    println(e)
+}
\ No newline at end of file