diff --git a/src/main/java/ic/doc/RpnCalculatorGui.java b/src/main/java/ic/doc/RpnCalculatorGui.java
index 9310481..3ab32b6 100644
--- a/src/main/java/ic/doc/RpnCalculatorGui.java
+++ b/src/main/java/ic/doc/RpnCalculatorGui.java
@@ -3,6 +3,8 @@ package ic.doc;
 import javax.swing.JFrame;
 import javax.swing.JPanel;
 import javax.swing.JTextField;
+import javax.swing.JButton;
+import java.util.stream.IntStream;
 
 public class RpnCalculatorGui {
   private final int defaultWidth;
@@ -10,6 +12,10 @@ public class RpnCalculatorGui {
 
   private static final int RESULT_FIELD_WIDTH = 10;
 
+  // Define the range of numbers that can be input to the calculator
+  private static final int MIN_INPUT_NUMBER = 0;
+  private static final int MAX_INPUT_NUMBER = 9;
+
   public static RpnCalculatorGui withDimensions(int defaultWidth, int defaultHeight) {
     return new RpnCalculatorGui(defaultWidth, defaultHeight);
   }
@@ -25,6 +31,12 @@ public class RpnCalculatorGui {
 
     JPanel panel = new JPanel();
 
+    // Add buttons for each number input
+    IntStream.rangeClosed(MIN_INPUT_NUMBER, MAX_INPUT_NUMBER).forEach(n -> {
+      JButton button = new JButton(Integer.toString(n));
+      panel.add(button);
+    });
+
     JTextField resultField = new JTextField(RESULT_FIELD_WIDTH);
     panel.add(resultField);