diff --git a/src/bitmap.c b/src/bitmap.c
index d50e7d6..b9252b7 100644
--- a/src/bitmap.c
+++ b/src/bitmap.c
@@ -14,10 +14,16 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor Boston, MA 02110-1301,  USA
  */
 
+/**
+ * @file
+ * @brief Functions for work with image bitmaps
+ */
+
 #include "common.h"
 #include "bitmap.h"
 
-unsigned char dict[256] = {
+/** bictionary for speedup bitmap comparing */
+static unsigned char dict[256] = {
 /* 0x00 _0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _A _B _C _D _E _F */
 /* ---------------------------------------------------- */
 /* 0_ */ 0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
diff --git a/src/bitmap.h b/src/bitmap.h
index b44ba06..e044083 100644
--- a/src/bitmap.h
+++ b/src/bitmap.h
@@ -53,7 +53,7 @@ simdb_bitmap_unpack(const unsigned char *map,
 /**
  * @brief Print bitmap to stdout as ascii-square
  * @param map Source bitmap
- * @note Heigth of "square" is equals to BITMAP_SIDE,
+ * @note Height of "square" is equals to BITMAP_SIDE,
  *   but width is BITMAP_SIDE x 2, for ease of reading
  */
 void
diff --git a/src/database.c b/src/database.c
index 2501604..db11735 100644
--- a/src/database.c
+++ b/src/database.c
@@ -14,6 +14,11 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor Boston, MA 02110-1301,  USA
  */
 
+/**
+ * @file
+ * Common routines to work with database
+ */
+
 #include "common.h"
 #include "bitmap.h"
 #include "simdb.h"
@@ -24,17 +29,20 @@ struct _simdb_t {
   char path[PATH_MAX];  /**< path to database file */
 };
 
+/** read some records from database file and checks for errors */
 #define DB_READ(db, buf, len, off) \
   errno = 0; \
   memset((buf), 0x0, (len)); \
   bytes = pread((db)->fd, (buf), (len), (off)); \
   if (errno) { return SIMDB_ERR_SYSTEM; }
 
+/** write some records from database file and checks for errors */
 #define DB_WRITE(db, buf, len, off) \
   errno = 0; \
   bytes = pwrite((db)->fd, (buf), (len), (off)); \
   if (errno) { return SIMDB_ERR_SYSTEM; }
 
+/** database header format line */
 const char *simdb_hdr_fmt = "IMDB v%02u, CAPS: %s;";
 
 bool