From: cat AT animal DOT u-net DOT com
Subject: Running DJGPP binaries on Ramdisk
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Newsgroups: comp.os.msdos.djgpp
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Date: 29 Sep 2000 15:55:05 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

                        DJGPP AND RAMDISK

    I mentioned problems with running DJGPP binaries in a previous post.
Recently I got a more recent version of dpmi (CSDPMI4B.ZIP) from a
simtelnet mirror site at src.docs.ic.ac.uk. The system seems to work
fine for very small (well 87K isn't so much really) binaries which do
not use any exotic features. To test I run on a 4Mb ramdrive although a
24-32Mb virtual disk will be no problem with modern day out of the box
multi-media systems.

    "config.sys"
    device=a:\himem.sys
    device=a:\ramdrive.sys 4096 512 256 /e

    "autoexec.bat"
    rem protect root directory of d: in case of second hd
    mkdir d:\d4
    d:
    cd \d4
    copy a:command.com
    set comspec=d:\d4\command.com
    copy a:cwsdpmi
    copy a:hello.exe
    hello

    "hello.c"
    main()
    {
       printf("Hello World!\n");
    }

    All of this works really fine. Hello.exe finds cwsdpmi in the
current directory and prints out the greeting message. I also tested
with a slightly more complicated program, pi.c which was taken from
the maths.faq.

   "pi.c"
   int a=10000,b,c=2800,d,e,f[2801],g;main(){for(;b-c;)f[b++]=a/5;
   for(;d=0,g=c*2;c-=14,printf("%.4d",e+d/a),e=d%a)for(b=c;d+=f[b]*a,
   f[b]=d%--g,d/=g--,--b;d*=b);}

   This one goes on and prints out 800 digits of pi in a blink.

   Now let's try my own maths program: d4x.exe which can compute
Bernouilli numbers, solve Pell's equation, generate RSA encryption keys
and read and write tar archives inter alia. This program is about 200K
after being stripped and it would be nice to get it running on the
ram disk. It's got bit mapped graphics so the equations can be
presented in a weird fonts if rquired. The command line is something
like

    d4x test.afn x=ada#tab_b50

    and it should print a sequence of lines like

1/1,-1/2,1/6,,-1/30,,1/42,,-1/30,,5/66,,-691/2730 etc. going on for
hundreds and hundreds of digits. But what do I get ? Just a very
cryptic message.

    D:\D4>d4x test.afn x=ada#tab_b50

    OMPT=: cannot open       cryptic error message.

    Because the binaries hello.exe and pi.exe work happily enough
there must be something wrong with my program. The same code works
well enough on windows and hard disk based DOS, and the same script
with slightly modified C works on the Linux console and also on
several of the Linux X-windows terminal emulators.

    The next thing is to try and find out just how well some other
programs like the ramdisk. Could I superzip the DJGPP onto a
single floppy, decompress to ramdrive and compile an application
such as a multi-tasking windows manager ? That would be great !
The FAQ says there is a little program called go32-v2.exe which
will report dpmi resources. I tried running this.

    D:\D4>go32-v2

    OMPT=: cannot open

    Yes. It's the same error message. Luckily I got the CSDPMI
source so at least I could grep all of the source files for bits of
the message. Nothing to do with the dpmi server.


               Tony Goddard
               http://www.d4maths.co.uk