diff --git a/rustbook/hello_cargo/src/main.rs b/rustbook/hello_cargo/src/main.rs
index e7a11a9..292e63b 100644
--- a/rustbook/hello_cargo/src/main.rs
+++ b/rustbook/hello_cargo/src/main.rs
@@ -1,3 +1,9 @@
 fn main() {
     println!("Hello, world!");
+
+    println!("0x{:x}", 0b1111_1010_1111_1010_1111_1010_1111);
+    println!("0b{:b}", 0xfafafaf);
+    println!("{}", 0xfafafaf);
+    println!("{}", 0xfeefee);
+    println!("0b{:b}", 0xfeefee);
 }