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VCOMP.TXT
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2009-12-11
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From: French Luser <Gary.Kild...@Digital.Research.com>
Newsgroups: comp.os.cpm
Subject: Re: What's the difference?
Date: Wed, 18 Oct 2006 13:41:40 +0200
Message-ID: <fa4cj2liedu142r6f54ln6e39drjlvbhpm@4ax.com>
References: <452106c6$0$27382$ba4acef3@news.orange.fr> <1159800668.846133.265440@b28g2000cwb.googlegroups.com>
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Hello, "Old Timer (John)"!
Many thanks for pointing me to VCOMP.
Last night, I tested it. Read below what I did.
Would you mind telling me/us what more you can say about VCOMP?
(What is the size of the biggest file you compared?)
Yours Sincerely,
"French Luser"
VCOMP.TXT
---------
Ok. I have finally had enough time to try the VCOMP program
mentioned by "Old Timer (John)" in response to my "What's the
difference?" message.
VCOMP stands for "Visual Compare". I found Version 1.52 on the
Internet, made by one John R. Whitney in 1992. The MS-DOS EXE
file is 30 KB, but I suspect that it is a self-expanding
program, since I saw strange-looking message strings when I
dumped it.
Among other things, I found that it works under MS-DOS 2.1+, has
a maximum line length of 2,048 characters, and a maximum number
of lines of 16,368 lines. Somewhere, the doc says: "Visual
Compare keeps the contents of the files you are comparing in
memory. Visual Compare can use up to 4 Megabytes of DOS memory."
So, I copied twice the source code of ASM-86, but I got the
error message: "Out of memory". I then reduced both files to be
16,368-lines long: same error message. I then continued reducing
both files, until I reached 15,000 lines and quit: Visual
Compare was still unable to deal with them, even when they were
only 222 Kilobytes long.
I then tried VCOMP with a smaller size of files. Remembering
LLLFPP (the Lawrence Livermore Laboratory Floating-Point Package
that was mentioned a few days ago in the comp.os.cpm Newsgroup),
I decided to have a go. You may remember that there are at least
3 versions: 2 from Volumes 2 and 10 of the CP/M User's Group
"Software Library", and 1 that I retyped. The first 2 are about
62 Kb in size, while mine is about 42 Kb.
After a few trials and re-reading the provided doc file the
appropriate number of times, I finally understood a little how
it works. It is, for sure, a change from line-oriented programs!
It also use quite a lot colors, while I almost never use them,
since I started with a daisy-wheel printer (which had, in fact,
some bi-color capability, but I never used it).
If you type VCOMP on the command line, you get a screenful with
some information. You are supposed to type the filespec of the
the first file, use the <Down Arrow> key to go where to type the
filespec of the second file, then either press ENTER or re-use
the <Down Arrow> to go to the "Options" line, etc.
The other way is more CP/M-like, as a command line. You type
VCOMP filespec1 filespec2 /options. I could not find any
interesting option, so just used the defaults.
There are several mentions of a "composite file", but I have not
reached this level, so far. (Apparently, it is a file made with
the first file and the line(s) differing from the second file.)
One important key is the F6 key: it enables you to see 1) file
one, 2) file two, or 3) both files. In this latter case, another
Function key appears, F9, which enables you to display them
side-by-side (you also have the option of displaying them one
above the other).
One curiosity is that, while displaying both files with F6
(before you press F9), the common contents of both files are
displayed in white chars, while the line(s) differing from file
1 and file 2 are displayed in different colors! (Both filespecs
are shown, on the title line. That's the only difference.
There is not a status line, like with WordStar.) It took me
quite a while you understand this way of doing. I prefer the
side-by-side display, but it is slower to scroll.
So, I simply typed VCOMP FPVOL2.ASM FPVOL10.ASM, then pressed
the F9 key to see them side-by-side. When you display a file
only, the <Page Down> key works, so you can scroll quickly up
and down. But, when you display 2 files side-by-side, only the
<Down Arrow> key (one line up) works, so the scrolling is much
slower.
In the present case, the differences between the LLLFPP found in
Volumes 2 and 10 are displayed on the screen in different
colors, with the common code in white characters. At a glance,
it is thus obvious that they are almost the same: only the
EQUates at the beginning, and a ORG at the end, are different.
However, when I tried VCOMP with my version, it was totally
confused, and could not recognize a single common line with the
2 old files, despite the fact that the code is 99% identical!
(It seems totally confused by the comments (";") lines of an
assembly language program.)
So, I think that VCOMP was used to compare high-level source
code files, not assembly language files. I could not find a way
to tell it to skip the EQUates at the beginning, then to
concentrate on the labels and mnemonics.
Among the doc, it is also mentioned that "Visual Compare (...)
produce a shortest possible sequence of insertions and deletions
that will convert FILEONE to FILETWO." So, this seems to be the
goal of this program: to synchronize 2 high-level program source
codes. (Why not simply copy the last file?)
I have not yet decided if I am going to write a COMPASM.BAS
program. At least, the VCOMP doc file gives the reference of the
algorithm used.
Yours Sincerely,
"French Luser"
EOF