diff --git a/09-go-type-system/01-bits/main.go b/09-go-type-system/01-bits/main.go
index 1ce938d..33de6e2 100644
--- a/09-go-type-system/01-bits/main.go
+++ b/09-go-type-system/01-bits/main.go
@@ -7,7 +7,10 @@
 
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"strconv"
+)
 
 func main() {
 	// %b verb prints bits
@@ -43,4 +46,46 @@ func main() {
 	fmt.Printf("%08b = %d\n", 32, 32)
 	fmt.Printf("%08b = %d\n", 64, 64)
 	fmt.Printf("%08b = %d\n", 128, 128)
+
+	// ------------------------------------------------
+	// How to calculate bits?
+	// ------------------------------------------------
+
+	// note: ^ means power of.
+	//       for example: 2^2 means 2 * 2     = 4
+	//                or: 2^3 means 2 * 2 * 2 = 8
+
+	// 0 0 0 0 0 0 1 0 is equal to 2 because:
+	// ^ ^ ^ ^ ^ ^ ^ ^
+	// | | | | | | | |
+	// | | | | | | | +-> 2^0 * 0 = 0
+	// | | | | | | +---> 2^1 * 1 = 2
+	// | | | | | +-----> 2^2 * 0 = 0
+	// | | | | +-------> 2^3 * 0 = 0
+	// | | | +---------> 2^4 * 0 = 0
+	// | | +-----------> 2^5 * 0 = 0
+	// | +-------------> 2^6 * 0 = 0
+	// +---------------> 2^7 * 0 = 0
+	//                   ------------+
+	//                             2
+
+	i, _ := strconv.ParseInt("00000010", 2, 64)
+	fmt.Println(i)
+
+	// 0 0 0 1 0 1 1 0 is equal to 2 because:
+	// ^ ^ ^ ^ ^ ^ ^ ^
+	// | | | | | | | |
+	// | | | | | | | +-> 2^0 * 0 = 0
+	// | | | | | | +---> 2^1 * 1 = 2
+	// | | | | | +-----> 2^2 * 1 = 4
+	// | | | | +-------> 2^3 * 0 = 0
+	// | | | +---------> 2^4 * 1 = 16
+	// | | +-----------> 2^5 * 0 = 0
+	// | +-------------> 2^6 * 0 = 0
+	// +---------------> 2^7 * 0 = 0
+	//                   ------------+
+	//                             22
+
+	i, _ = strconv.ParseInt("00010110", 2, 64)
+	fmt.Println(i)
 }