diff --git a/lib/ac-api/src/main/java/org/applecommander/device/TrackSectorDevice.java b/lib/ac-api/src/main/java/org/applecommander/device/TrackSectorDevice.java
index 3ac36f8c..d5e817b7 100644
--- a/lib/ac-api/src/main/java/org/applecommander/device/TrackSectorDevice.java
+++ b/lib/ac-api/src/main/java/org/applecommander/device/TrackSectorDevice.java
@@ -19,6 +19,7 @@
  */
 package org.applecommander.device;
 
+import org.applecommander.device.Coordinate.TrackAndSectorCoordinate;
 import org.applecommander.util.DataBuffer;
 import org.applecommander.util.InformationGroup;
 import org.applecommander.util.InformationProvider;
@@ -102,6 +103,12 @@ public interface TrackSectorDevice extends Device {
         public int deviceSize() {
             return sectorsPerDisk() * SECTOR_SIZE;
         }
+        public int calculateSectorOffset(int track, int sector) {
+            return track * sectorsPerTrack + sector;
+        }
+        public TrackAndSectorCoordinate sectorOffsetToCoordinate(int sectorOffset) {
+            return new TrackAndSectorCoordinate(sectorOffset / sectorsPerTrack, sectorOffset % sectorsPerTrack);
+        }
 
         @Override
         public List<InformationGroup> information() {
diff --git a/lib/ac-api/src/main/java/org/applecommander/os/SequentialAllocator.java b/lib/ac-api/src/main/java/org/applecommander/os/SequentialAllocator.java
new file mode 100644
index 00000000..4d5fdbee
--- /dev/null
+++ b/lib/ac-api/src/main/java/org/applecommander/os/SequentialAllocator.java
@@ -0,0 +1,51 @@
+package org.applecommander.os;
+
+import org.applecommander.util.Range;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+
+/// The SequentialAllocator is intended to handle what is, essentially, a
+/// single dimension allocation. That is, if the disk is allocated by sequential
+/// chunks, this allocator should support it. For images that use T/S geometry
+/// instead of block geometry, the T/S will need to be transformed.
+///
+/// For instance, GameDOS allocates by T/S but allocates all in a chunk. So once
+/// there is a starting place, the rest of the file follows in a very specific
+/// order.
+public class SequentialAllocator {
+    private final int totalSize;
+    private final List<Range> used = new ArrayList<>();
+
+    public SequentialAllocator(int totalSize) {
+        this.totalSize = totalSize;
+    }
+
+    public void addUsed(int first, int last) {
+        assert first <= last;
+        assert first < totalSize && last <= totalSize;
+        used.add(new Range(first, last));
+    }
+    public void addUsedByLength(int first, int length) {
+        addUsed(first, first+length-1);
+    }
+
+    /// Look for `requestSize` spaces between the used ranges.
+    /// Returns either the first placement that the request will fit
+    /// or a `-1` if there is no fit.
+    public int find(int requestSize) {
+        used.sort(Comparator.comparingInt(Range::first));
+        int start = 0;
+        for (Range range : used) {
+            if (range.first() - start >= requestSize) {
+                return start;
+            }
+            start = range.last() + 1;
+        }
+        if (totalSize - start >= requestSize) {
+            return start;
+        }
+        return -1;
+    }
+}
diff --git a/lib/ac-api/src/test/java/org/applecommander/os/SequentialAllocatorTest.java b/lib/ac-api/src/test/java/org/applecommander/os/SequentialAllocatorTest.java
new file mode 100644
index 00000000..4888c2f8
--- /dev/null
+++ b/lib/ac-api/src/test/java/org/applecommander/os/SequentialAllocatorTest.java
@@ -0,0 +1,21 @@
+package org.applecommander.os;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class SequentialAllocatorTest {
+    @Test
+    public void test() {
+        SequentialAllocator allocator = new SequentialAllocator(10);
+        allocator.addUsed(2,4);
+        allocator.addUsed(5,6);
+
+        // Allocation:
+        //    0123456789
+        //    FFUUUUUFFF
+        assertEquals(0, allocator.find(2));
+        assertEquals(7, allocator.find(3));
+        assertEquals(-1, allocator.find(4));
+    }
+}