diff --git a/src/obitypes.h b/src/obitypes.h
index 9484d85..023c640 100644
--- a/src/obitypes.h
+++ b/src/obitypes.h
@@ -21,10 +21,9 @@
 #define OBIInt_NA (INT32_MIN)		/**< NA value for the type OBI_INT */
 #define OBIIdx_NA (INT64_MIN)		/**< NA value for indices */
 #define OBIFloat_NA (float_NA())	/**< NA value for the type OBI_FLOAT */
-#define OBIChar_NA (0)				/**< NA value for the type OBI_CHAR */
-										 // TODO not sure about this one as it can be impossible to distinguish from uninitialized values
-#define OBISeq_NA ("\0")			// TODO
-#define OBIStr_NA ("\0")			// TODO
+#define OBIChar_NA (0)				/**< NA value for the type OBI_CHAR */ // TODO not sure about this one as it can be impossible to distinguish from uninitialized values
+#define OBISeq_NA ("\0")			/**< NA value for the type OBI_SEQ */  // TODO discuss
+#define OBIStr_NA ("\0")			/**< NA value for the type OBI_STR */  // TODO discuss
 
 
 /**
@@ -48,19 +47,23 @@ typedef enum OBIType {
 	OBI_CHAR,					/**< a character (C type : char) */
 	OBI_STR,				    /**< an index in a data structure (C type : int64_t) referring to a character string */
 	OBI_SEQ,					/**< an index in a data structure (C type : int64_t) referring to a DNA sequence */
-	OBI_IDX					    /**< an index referring to a line in another column (C type : int64_t) */	// TODO delete?
+	OBI_IDX					    /**< an index referring to a line in another column (C type : int64_t) */
 } OBIType_t, *OBIType_p;
 
 
-typedef int64_t index_t;
+/**
+ * Typedefs for the OBITypes.
+ */
 typedef int32_t obiint_t;
 typedef double obifloat_t;
 typedef char obichar_t;
-// TODO same for obistr_t and obiseq_t ?
+typedef int64_t index_t;
 
+typedef char byte_t;			/**< Defining byte type.
+ 	 	 	 	 	 	 	 	 */
 
-typedef char byte_t;		/**< Defining byte type.
- 	 	 	 	 	 	 	 */
+typedef int32_t obiversion_t;	/**< Defining type for version numbers.
+	 	 	 	 	 	 	 	 */
 
 
 /**
@@ -104,7 +107,7 @@ size_t obi_sizeof(OBIType_t type);
  * @brief Returns the size required to store an array of elements with an OBIType.
  *
  * The returned size is large enough to store an array large enough
- * to store all the elements but rounded at a multiple of the memory page size.				// TODO this might be redundant but still a good thing
+ * to store all the elements but rounded at a multiple of the memory page size.
  *
  * @param data_type The OBIType of the elements.
  * @param nb_lines The number of lines to be stored.