diff --git a/include/apple2.enc.h b/include/apple2.enc.h
index 5cd23ad..6f8068b 100644
--- a/include/apple2.enc.h
+++ b/include/apple2.enc.h
@@ -9,7 +9,55 @@
  * with using other values for it, and this one in particular is used in
  * WinApple, so I went with it.
  */
-#define ENC_VOLUME  0xfe
+#define ENC_VOLUME 0xfe
+
+/*
+ * The number of tracks that a DOS 3.3 disk would have.
+ */
+#define ENC_NUM_TRACKS 35
+
+/*
+ * The number of sectors within a single track of data for a DOS 3.3
+ * disk.
+ */
+#define ENC_NUM_SECTORS 16
+
+/*
+ * A decoded sector is 256 bytes long
+ */
+#define ENC_DSECTOR 0x100
+
+/*
+ * And a track--being composed of 16 sectors--is 4096 bytes long, or 4k
+ * bytes. (256 * 16 = 4096)
+ */
+#define ENC_DTRACK 0x1000
+
+/*
+ * An encoded sector is 382 bytes long, and is comprised of a sector
+ * header plus padding bytes both before _and_ after the data field.
+ */
+#define ENC_ESECTOR 0x17e
+
+/*
+ * An encoded track contains 16 sectors, as mentioned for ENC_DTRACK.
+ * But it also contains some additional padding (48 bytes-worth).
+ */
+#define ENC_ETRACK 0x1810
+
+/*
+ * A sector header consists of some byte markers--all byte markers in
+ * 6-and-2 encoding are 3 bytes long--and also some metadata, such as
+ * the track number, the sector number, the volume, and an XOR'd
+ * combination of all three.
+ */
+#define ENC_ESECTOR_HEADER 0xe
+
+/*
+ * The track header (as mentioned for ENC_ETRACK) is 48 bytes of--well,
+ * nothing really, just padding.
+ */
+#define ENC_ETRACK_HEADER 0x30
 
 extern int apple2_enc_4n4(vm_segment *, int, vm_8bit); 
 extern int apple2_enc_sector(vm_segment *, vm_segment *, int, int);