Re: LZ: Delete Strings in ASM?


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Re: LZ: Delete Strings in ASM?



On Wed, 25 Sep 1996, Mel Tsai wrote:


> Actually, it is possible.  The program would be complex, however.  You
> would first need to make sure your program was located in a lower
> memory position, otherwise it may get moved and all of a sudden the
> program crashes (I'm not sure when this will occur).  One solution
> would be to move your program to the graph memory, move programs, and
> then go back to your main program.  Probably the most difficult
> aspect, however, is knowing which variables you must update, i.e. free
> memory, vat and memory pointers, checksum, and of course moving the
> entire memory down.  One thing I did notice is that the ROM doesn't
> totally delete a file.  I deleted a zshell program, loaded hexview,
> and fragments of the program were still in memory.  I'm not sure what
> exactly happens.
 
The same thing is true on most computers, both in memory and
on disk.  There are pointers that tell the system where things
are and they can delete these things by removing the pointers
to them.


That's why, after you delete a file on a pc, you can use the
UNDELETE command to get it back.  In this case the pointer
is in the directory, which is just a table of files and
information about them.  The DEL command marks that directory
entry as deleted and then it's done its work.  The mark is
placed in the first character of the name, which is why you
have to give the first letter to the undelete command, since
it's been lost.


If you're a MAC user you probably won't understand this, but
then, MAC users aren't supposed to understand computers.  :)


Barry


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