Index: src/os_win.c
==================================================================
--- src/os_win.c
+++ src/os_win.c
@@ -452,19 +452,25 @@
 
 const sqlite3_mem_methods *sqlite3MemGetWin32(void);
 #endif /* SQLITE_WIN32_MALLOC */
 
 /*
-** The following variable is (normally) set once and never changes
-** thereafter.  It records whether the operating system is Win9x
-** or WinNT.
-**
-** 0:   Operating system unknown.
-** 1:   Operating system is Win9x.
-** 2:   Operating system is WinNT.
-**
-** In order to facilitate testing on a WinNT system, the test fixture
+** The following variables are (normally) set once and never change
+** thereafter.  They record the major and minor OS version and whether
+** the operating system type is Win9x or WinNT.
+**
+** sqlite3_os_type = 0:   Operating system type is unknown.
+** sqlite3_os_type = 1:   Operating system type is Win9x.
+** sqlite3_os_type = 2:   Operating system type is WinNT.
+**
+** For the major and minor versions, the following are the "well-known"
+** operating system releases (i.e. the ones that are tested for):
+**
+** sqlite3_os_major.sqlite3_os_minor = 6.0 = Windows Vista
+** sqlite3_os_major.sqlite3_os_minor = 6.2 = Windows 8
+**
+** In order to facilitate testing on WinNT systems, the test fixture
 ** can manually set this value to 1 to emulate Win98 behavior.
 */
 #ifdef SQLITE_TEST
 LONG SQLITE_WIN32_VOLATILE sqlite3_os_type = 0;
 LONG SQLITE_WIN32_VOLATILE sqlite3_os_major = 0;
@@ -3624,10 +3630,18 @@
 #endif
   }
   OSTRACE(("FCNTL file=%p, rc=SQLITE_NOTFOUND\n", pFile->h));
   return SQLITE_NOTFOUND;
 }
+
+/*
+** Same-volume determination for versions of Windows prior to Windows 8
+** is untested, undocumented, and unsupported.  All such code is omitted
+** unless the SQLITE_WIN32_VISTA_SECTOR_SIZE define is set at compile-time,
+** and that compile-time option is off by default and undocumented.  The
+** following code is for reference only.
+*/
 
 #if defined(SQLITE_WIN32_VISTA_SECTOR_SIZE) && \
     defined(_WIN32_WINNT) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
 /*
 ** This function attempts to determine if the specified file resides on the
@@ -3687,10 +3701,18 @@
       winLogError(SQLITE_IOERR_FSTAT, pFile->lastErrno,
                   "winSectorSize1", pFile->zPath);
     }
   }
 #endif
+
+/*
+** Sector-size determination for versions of Windows prior to Windows 8
+** is untested, undocumented, and unsupported.  All such code is omitted
+** unless the SQLITE_WIN32_VISTA_SECTOR_SIZE define is set at compile-time,
+** and that compile-time option is off by default and undocumented.  The
+** following code is for reference only.
+*/
 
 #if defined(SQLITE_WIN32_VISTA_SECTOR_SIZE) && \
     defined(_WIN32_WINNT) && _WIN32_WINNT >= _WIN32_WINNT_VISTA
   if( osIsVistaPlus() ){
     winFile *pFile = (winFile*)id;