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1995-03-18
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3KB
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71 lines
Search & Rescue Memory v1.0 - October l988
I learned assembler on a C-128. This fabulous machine has a very handy
built-in debugger with a lot of commands. The public domain debuggers I
got from this library and from other sources can do a lot, but they don't
have a decent Hunt (Find, Search) command that could salvage "lost" files
in memory after an accidental delete or reset. So I wrote S&R to do just
that. Suppose your system crashes while you are editing a text file: what
can you do? S&R may save your day; here's how.
First you have to reset the Amiga. As soon as the screen appears, type
"CTRL-D" to get a CLI. This is the quickest and least disturbing method to
regain control of the computer. Then, call S&R from that CLI. It opens two
windows, the upper one to read memory and the lower one for the other
commands. Choose the ASCII option for text and enter a string that was in
the lost file ("Dear Santa"). The standard Amiga user's memory is from $0
to $7ffff (512 K). With a 1 Meg Amiga, the lost file may also be found
between $c00000 and $c7ffff. The file you are looking for may have been
damaged if it was overwritten by some odd command during rebooting; in that
case, you may recover only a part of it. It may also be found in several
"chunks" if there was not enough contiguous memory to load it in one block.
In that case, you have to look for each chunk. S&R will show every occurence
of the string in the selected range. Check them up with the "M" option. Some
addresses may be overwritten by "0" or "2e" in blocks used as buffers. When
you find the missing file, note the start and end addresses and use the Save
option to salvage the block. Do not save to RAM: because this may shift away
the memory you are saving. With options "W" or "L", S&R will also look for
words (2 bytes) and long words (4 bytes) in hexadecimal. Just follow the
prompts and that's it.
Some parts of memory will not tolerate peeping toms and looking them up
crashes the computer. For a 1 Meg system, $0 - $7ffff and $c00000 - $c7ffff
are safe (you will find there all the user's programs and lost files).
Some Virus reside at $7ec00-$7f000. Explore the rest at your own risks;
crossing some "borders" (like $200000 and $120000) may give odd results.
As for speed, the all-ML S&R is quite fast: it will check $0-$100000
(more than a million bytes) in only 9 seconds. It is so small (just 2300
bytes) that it fits well in the "c" directory, too. Ah, one more thing: when
you enter hexadecimal addresses or data, you may skip any leading zero. A
Return at the start address prompt will get you back to the menu. If the
start address you entered is no good, enter a slightly higher value as an
end address before pressing Return.
Well, you know enough now to give it a try. Memory explorers would be
well advised to use a memory map to avoid the lurking Guru and his boring
advices. The source code is available from the author.
-*=*- Michel Laliberté -*=*-
Montréal, Québec