🚀 go-pugleaf

In article <15649@.la.locus.com>, dana@lando.la.locus.com (Dana H. Myers) writes:
> In article <Aug.15.13.24.38.1990.26985@remus.rutgers.edu> hobbit@remus.rutgers.edu (*Hobbit*) writes:
> >I installed a switch in my PC to deliberately open the write gate signal,
> >and damned if it doesn't prevent the controller from scribbling on the disk.
> 
> >Anyway,
> >the fun thing about this hack is that the controller has no clue whether
> >the write succeeded or not, and due to disk buffering, MSLoss really thinks
> >the new file is there, and you can even type it; but the next time you do a
> >DIR or something the buffers get flushed and the file mysteriously disappears.
> 
>    On MS-DOS, the shell (command.com) normally provides a command to
> enable or disable verification of disk writes. This is the 'verify'
> command. At the DOS prompt, issue the command 'verify'. You will be
> notified of the current state of verification ('on' or 'off'). If it is
> off, try setting it on; enter the command 'verify on'.

This is a common misconception.  When you enable VERIFY in MS-DOS
it only verifies that what is on the disk is readable.  It most
definitely does NOT compare what it reads to what what written.

The confusion is understandable given the terrible description
given in most DOS references.  For example, the MS-DOS
Encyclopedia description of VERIFY refers to COPY/V which says
(notes in [] are my comments):

	The /V switch causes a read-after-write verification of
	each block of the destination file [blatently
	misleading].  Its effect is equivalent to that of the
	VERIFY ON command [don't you just love circular
	definitions?].  No comparison is made between the source
	and destination files [finaly, the key phrase!] -- the /V
	switch simply causes MS-DOS to verify that the
	destination file has been written correctly [again
	somewhat misleading].

All that VERIFY does is call INT 13, Function 4, Verify Disk
Sectors, which just verifies that the sector is readable, not
that it contains any particular data.
----
Larry Jones                         UUCP: uunet!sdrc!thor!scjones
SDRC                                      scjones@thor.UUCP
2000 Eastman Dr.                    BIX:  ltl
Milford, OH  45150-2789             AT&T: (513) 576-2070
It doesn't have a moral, does it?  I hate being told how to live my life.
-- Calvin