diff --git a/src/main/java/de/neemann/digital/core/IntFormat.java b/src/main/java/de/neemann/digital/core/IntFormat.java
index ffa09e5b1..8c6bafc8f 100644
--- a/src/main/java/de/neemann/digital/core/IntFormat.java
+++ b/src/main/java/de/neemann/digital/core/IntFormat.java
@@ -90,6 +90,24 @@ public enum IntFormat {
         }
     }
 
+    public int strLen(int bits) {
+        switch (this) {
+            case dec:
+                return (int) Math.ceil(Math.log10(1L<<bits));
+            case decSigned:
+                return (int) Math.ceil(Math.log10(1L<<(bits-1)))+1;
+            case hex:
+                return (bits-1)/4+3;
+            case bin:
+                return bits+2;
+            case oct:
+                return (bits-1)/3+3;
+            case ascii:
+                return 3;
+            default:
+                return (bits-1)/4+3;
+        }
+    }
 
     private static final char[] DIGITS = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
 
diff --git a/src/main/java/de/neemann/digital/core/memory/EEPROM.java b/src/main/java/de/neemann/digital/core/memory/EEPROM.java
index b21034f44..4e1220dc8 100644
--- a/src/main/java/de/neemann/digital/core/memory/EEPROM.java
+++ b/src/main/java/de/neemann/digital/core/memory/EEPROM.java
@@ -31,6 +31,7 @@ public class EEPROM extends Node implements Element, RAMInterface, ROMInterface
             .addAttribute(Keys.BITS)
             .addAttribute(Keys.ADDR_BITS)
             .addAttribute(Keys.LABEL)
+            .addAttribute(Keys.INT_FORMAT)
             .addAttribute(Keys.IS_PROGRAM_MEMORY)
             .addAttribute(Keys.INVERTER_CONFIG)
             .addAttribute(Keys.DATA);
@@ -42,6 +43,7 @@ public class EEPROM extends Node implements Element, RAMInterface, ROMInterface
     private final String label;
     private final ObservableValue dataOut;
     private final boolean isProgramMemory;
+    private final IntFormat intFormat;
     private DataField memory;
     private ObservableValue addrIn;
     private ObservableValue csIn;
@@ -74,6 +76,7 @@ public class EEPROM extends Node implements Element, RAMInterface, ROMInterface
                 .setPinDescription(DESCRIPTION)
                 .setBidirectional();
         isProgramMemory = attr.get(Keys.IS_PROGRAM_MEMORY);
+        intFormat = attr.get(Keys.INT_FORMAT);
     }
 
     @Override
@@ -122,6 +125,11 @@ public class EEPROM extends Node implements Element, RAMInterface, ROMInterface
         }
     }
 
+    @Override
+    public IntFormat getIntFormat() {
+        return intFormat;
+    }
+
     @Override
     public ObservableValues getOutputs() {
         return dataOut.asList();
diff --git a/src/main/java/de/neemann/digital/core/memory/RAMDualPort.java b/src/main/java/de/neemann/digital/core/memory/RAMDualPort.java
index 2d7400e15..f1e19ba66 100644
--- a/src/main/java/de/neemann/digital/core/memory/RAMDualPort.java
+++ b/src/main/java/de/neemann/digital/core/memory/RAMDualPort.java
@@ -30,10 +30,12 @@ public class RAMDualPort extends Node implements Element, RAMInterface {
             .addAttribute(Keys.ROTATE)
             .addAttribute(Keys.BITS)
             .addAttribute(Keys.ADDR_BITS)
+            .addAttribute(Keys.INT_FORMAT)
             .addAttribute(Keys.IS_PROGRAM_MEMORY)
             .addAttribute(Keys.LABEL);
 
     private DataField memory;
+    private final IntFormat intFormat;
     private final ObservableValue output;
     private final int addrBits;
     private final int bits;
@@ -63,6 +65,7 @@ public class RAMDualPort extends Node implements Element, RAMInterface {
         memory = createDataField(attr, size);
         label = attr.getLabel();
         isProgramMemory = attr.get(Keys.IS_PROGRAM_MEMORY);
+        intFormat = attr.get(Keys.INT_FORMAT);
     }
 
     /**
@@ -181,6 +184,11 @@ public class RAMDualPort extends Node implements Element, RAMInterface {
         }
     }
 
+    @Override
+    public IntFormat getIntFormat() {
+        return intFormat;
+    }
+
     /**
      * Sets the used memory field
      *
diff --git a/src/main/java/de/neemann/digital/core/memory/RAMInterface.java b/src/main/java/de/neemann/digital/core/memory/RAMInterface.java
index 1238ca24e..29a245338 100644
--- a/src/main/java/de/neemann/digital/core/memory/RAMInterface.java
+++ b/src/main/java/de/neemann/digital/core/memory/RAMInterface.java
@@ -5,6 +5,7 @@
  */
 package de.neemann.digital.core.memory;
 
+import de.neemann.digital.core.IntFormat;
 import de.neemann.digital.core.stats.Countable;
 
 /**
@@ -25,4 +26,8 @@ public interface RAMInterface extends ProgramMemory, Countable {
      * @return the addr bits
      */
     int getAddrBits();
+
+    default IntFormat getIntFormat() {
+        return IntFormat.hex;
+    }
 }
diff --git a/src/main/java/de/neemann/digital/core/memory/ROM.java b/src/main/java/de/neemann/digital/core/memory/ROM.java
index f8614cba8..3c40690dd 100644
--- a/src/main/java/de/neemann/digital/core/memory/ROM.java
+++ b/src/main/java/de/neemann/digital/core/memory/ROM.java
@@ -38,10 +38,12 @@ public class ROM extends Node implements Element, ROMInterface, ProgramMemory {
             .addAttribute(Keys.ADDR_BITS)
             .addAttribute(Keys.LABEL)
             .addAttribute(Keys.DATA)
+            .addAttribute(Keys.INT_FORMAT)
             .addAttribute(Keys.IS_PROGRAM_MEMORY)
             .addAttribute(Keys.AUTO_RELOAD_ROM);
 
     private DataField data;
+    private final IntFormat intFormat;
     private final ObservableValue output;
     private final int addrBits;
     private final int dataBits;
@@ -73,6 +75,7 @@ public class ROM extends Node implements Element, ROMInterface, ProgramMemory {
             hexFile = attr.getFile(LAST_DATA_FILE_KEY);
         } else
             hexFile = null;
+        intFormat = attr.get(Keys.INT_FORMAT);
     }
 
     @Override
@@ -140,6 +143,11 @@ public class ROM extends Node implements Element, ROMInterface, ProgramMemory {
         return addrBits;
     }
 
+    @Override
+    public IntFormat getIntFormat() {
+        return intFormat;
+    }
+
     @Override
     public int getDataBits() {
         return dataBits;
diff --git a/src/main/java/de/neemann/digital/core/memory/rom/ROMInterface.java b/src/main/java/de/neemann/digital/core/memory/rom/ROMInterface.java
index 05e58d10f..5aaad88a3 100644
--- a/src/main/java/de/neemann/digital/core/memory/rom/ROMInterface.java
+++ b/src/main/java/de/neemann/digital/core/memory/rom/ROMInterface.java
@@ -5,6 +5,7 @@
  */
 package de.neemann.digital.core.memory.rom;
 
+import de.neemann.digital.core.IntFormat;
 import de.neemann.digital.core.memory.DataField;
 import de.neemann.digital.core.stats.Countable;
 
@@ -34,4 +35,5 @@ public interface ROMInterface extends Countable {
      */
     int getAddrBits();
 
+    IntFormat getIntFormat();
 }
diff --git a/src/main/java/de/neemann/digital/draw/shapes/RAMShape.java b/src/main/java/de/neemann/digital/draw/shapes/RAMShape.java
index fbb35c972..1bfa5db62 100644
--- a/src/main/java/de/neemann/digital/draw/shapes/RAMShape.java
+++ b/src/main/java/de/neemann/digital/draw/shapes/RAMShape.java
@@ -71,8 +71,9 @@ public class RAMShape extends GenericShape {
             @Override
             public boolean clicked(CircuitComponent cc, Point pos, IOState ioState, Element element, SyncAccess modelSync) {
                 if (element instanceof RAMInterface) {
-                    DataField dataField = ((RAMInterface) element).getMemory();
-                    DataEditor dataEditor = new DataEditor(cc, dataField, dataBits, addrBits, true, modelSync);
+                    RAMInterface ram = (RAMInterface) element;
+                    DataField dataField = ram.getMemory();
+                    DataEditor dataEditor = new DataEditor(cc, dataField, dataBits, addrBits, true, modelSync, ram.getIntFormat());
                     dataEditor.showDialog(dialogTitle, model);
                 }
                 return false;
diff --git a/src/main/java/de/neemann/digital/gui/components/DataEditor.java b/src/main/java/de/neemann/digital/gui/components/DataEditor.java
index 4bf68ff46..e3985ec13 100644
--- a/src/main/java/de/neemann/digital/gui/components/DataEditor.java
+++ b/src/main/java/de/neemann/digital/gui/components/DataEditor.java
@@ -5,10 +5,7 @@
  */
 package de.neemann.digital.gui.components;
 
-import de.neemann.digital.core.Bits;
-import de.neemann.digital.core.Model;
-import de.neemann.digital.core.ModelEvent;
-import de.neemann.digital.core.SyncAccess;
+import de.neemann.digital.core.*;
 import de.neemann.digital.core.memory.DataField;
 import de.neemann.digital.core.memory.importer.Importer;
 import de.neemann.digital.gui.SaveAsHelper;
@@ -53,7 +50,7 @@ public class DataEditor extends JDialog {
      * @param modelIsRunning true if model is running
      * @param modelSync      used to access the running model
      */
-    public DataEditor(Component parent, DataField dataField, int dataBits, int addrBits, boolean modelIsRunning, SyncAccess modelSync) {
+    public DataEditor(Component parent, DataField dataField, int dataBits, int addrBits, boolean modelIsRunning, SyncAccess modelSync, IntFormat intFormat) {
         super(SwingUtilities.windowForComponent(parent), Lang.get("key_Data"), modelIsRunning ? ModalityType.MODELESS : ModalityType.APPLICATION_MODAL);
         setDefaultCloseOperation(DISPOSE_ON_CLOSE);
 
diff --git a/src/main/java/de/neemann/digital/gui/components/EditorFactory.java b/src/main/java/de/neemann/digital/gui/components/EditorFactory.java
index 3b95b0278..150e86d90 100644
--- a/src/main/java/de/neemann/digital/gui/components/EditorFactory.java
+++ b/src/main/java/de/neemann/digital/gui/components/EditorFactory.java
@@ -606,7 +606,7 @@ public final class EditorFactory {
                         getAttributeDialog().storeEditedValues();
                         int dataBits = attr.get(Keys.BITS);
                         int addrBits = getAddrBits(attr);
-                        DataEditor de = new DataEditor(panel, data, dataBits, addrBits, false, SyncAccess.NOSYNC);
+                        DataEditor de = new DataEditor(panel, data, dataBits, addrBits, false, SyncAccess.NOSYNC, attr.get(Keys.INT_FORMAT));
                         de.setFileName(attr.getFile(ROM.LAST_DATA_FILE_KEY));
                         if (de.showDialog()) {
                             DataField mod = de.getModifiedDataField();
diff --git a/src/main/java/de/neemann/digital/gui/components/ProbeDialog.java b/src/main/java/de/neemann/digital/gui/components/ProbeDialog.java
index 1dbec84ba..0e8691b03 100644
--- a/src/main/java/de/neemann/digital/gui/components/ProbeDialog.java
+++ b/src/main/java/de/neemann/digital/gui/components/ProbeDialog.java
@@ -88,7 +88,7 @@ public class ProbeDialog extends JDialog implements ModelStateObserverTyped {
                                     ram.getDataBits(),
                                     ram.getAddrBits(),
                                     true,
-                                    model).showDialog(ram.getLabel(), model);
+                                    model, ram.getIntFormat()).showDialog(ram.getLabel(), model);
                         }
                     }));
                 }
diff --git a/src/main/java/de/neemann/digital/gui/components/ROMEditorDialog.java b/src/main/java/de/neemann/digital/gui/components/ROMEditorDialog.java
index c6d780a9e..223811dfa 100644
--- a/src/main/java/de/neemann/digital/gui/components/ROMEditorDialog.java
+++ b/src/main/java/de/neemann/digital/gui/components/ROMEditorDialog.java
@@ -138,7 +138,7 @@ public class ROMEditorDialog extends JDialog {
         }
 
         public boolean edit(ROMEditorDialog romEditorDialog) {
-            DataEditor de = new DataEditor(romEditorDialog, data, ri.getDataBits(), ri.getAddrBits(), false, SyncAccess.NOSYNC);
+            DataEditor de = new DataEditor(romEditorDialog, data, ri.getDataBits(), ri.getAddrBits(), false, SyncAccess.NOSYNC, ri.getIntFormat());
             if (de.showDialog()) {
                 data = de.getModifiedDataField();
                 return true;
diff --git a/src/test/java/de/neemann/digital/core/IntFormatTest.java b/src/test/java/de/neemann/digital/core/IntFormatTest.java
index 452788f23..f5e1bb428 100644
--- a/src/test/java/de/neemann/digital/core/IntFormatTest.java
+++ b/src/test/java/de/neemann/digital/core/IntFormatTest.java
@@ -86,4 +86,34 @@ public class IntFormatTest extends TestCase {
             assertTrue(format.name() + ":" + val + " != " + conv, val.isEqual(conv));
         }
     }
+
+    public void testStrLen() {
+        assertEquals(6,IntFormat.hex.strLen(16));
+        assertEquals(6,IntFormat.hex.strLen(15));
+        assertEquals(6,IntFormat.hex.strLen(14));
+        assertEquals(6,IntFormat.hex.strLen(13));
+        assertEquals(5,IntFormat.hex.strLen(12));
+
+        assertEquals(18,IntFormat.bin.strLen(16));
+        assertEquals(17,IntFormat.bin.strLen(15));
+        assertEquals(16,IntFormat.bin.strLen(14));
+
+        assertEquals(3,IntFormat.dec.strLen(8));
+        assertEquals(3,IntFormat.dec.strLen(9));
+        assertEquals(4,IntFormat.dec.strLen(10));
+
+        assertEquals(4,IntFormat.decSigned.strLen(8));
+        assertEquals(4,IntFormat.decSigned.strLen(9));
+        assertEquals(4,IntFormat.decSigned.strLen(10));
+        assertEquals(5,IntFormat.decSigned.strLen(11));
+
+        assertEquals(4,IntFormat.oct.strLen(4));
+        assertEquals(4,IntFormat.oct.strLen(5));
+        assertEquals(4,IntFormat.oct.strLen(6));
+        assertEquals(5,IntFormat.oct.strLen(7));
+        assertEquals(5,IntFormat.oct.strLen(8));
+        assertEquals(5,IntFormat.oct.strLen(9));
+        assertEquals(6,IntFormat.oct.strLen(10));
+
+    }
 }