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From: rcwlobe@klipper.cs.vu.nl (Reg Lobee)
Newsgroups: comp.sys.cbm
Subject: Re: 154I drive problem
Keywords: 154I disk drive
Message-ID: <2142@botter.cs.vu.nl>
Date: 13 Apr 89 13:12:50 GMT
References: <3738@silver.bacs.indiana.edu>
Sender: news@cs.vu.nl
Lines: 23

In article <3738@silver.bacs.indiana.edu>, sl161004@silver.bacs.indiana.edu (David Chary) writes:
> Could someone please identify this problem with the 154I disk drive:
> 
> Suppose I have a number of files, "FILE A", "FILE B",... "FILE n".
> When I save FILE K using "@):FILE K", it does what it is told.
> But later, I want to use FILE G, which I know is a different file.
> so I load "FILE G" and much to my surprise it is "FILE K"!
> 
> What is happening to the disk or the drive?

Each name in a directory has a pointer to the first block of the file.
The 'save and replace' option works by first saving the new file to
disk and then changing these pointers from the old to the new file.
The blocks the old file used are marked 'free' after the operation.
Sometimes the DOS changes the wrong pointers so a file with another
name points to the file you just saved. The file which shouldn't
have been changed is now lost. In your question "FILE G".
I don't know exactly when this error occurs. Sometimes it does, but
mostly it doesn't.
To avoid this risk you better use the scratch command to delete
the old file and then save.

Reg Lobee, rcwlobe@cs.vu.nl