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From: kirchner@informatik.uni-kl.de (Reinhard Kirchner)
Newsgroups: comp.lang.misc,comp.sys.ibm.pc.misc,comp.sources.wanted
Subject: Re: Multiple-Precision Binary to ASCII Decimal Machine Languae Routine
Message-ID: <7565@uklirb.informatik.uni-kl.de>
Date: 19 Feb 91 11:39:07 GMT
References: <1991Feb18.155207.24378@ux1.cso.uiuc.edu>
Sender: news@uklirb.informatik.uni-kl.de
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From article <1991Feb18.155207.24378@ux1.cso.uiuc.edu>, by gwang@ncsa.uiuc.edu (George Wang):
> Does anyone know of a 8088 Machine Language routine that will
> convert a multiple-byte array containing a VERY large (64 bit, 8 bytes)
> number to ASCII? I know how to write a routine for 16 bit signed

There is a very simple algorithm to convert binaries of arbitrary length
to decimal WITHOUT division. I post it here since it may be of general
interest.

You need to arrays in storage, one for the decimal ( bcd ) number and one
for the binary.

    |---------------------------|-------------|
          bcd                       binary

Then you simply shift this whole thing to the left bitwise. So the bits
from the binary cross the border to the bcd-part. And now the conversion-trick:

if the rightmost digit in the bcd-part, the one where the binary bits go in,
is >= 5, then add 3 to this digit. On the next shift this will result in a
higher next digit.

So you shift and perhaps add 64 times in the above case.

To convert not to bcd but ASCII should be possible by adding not 3 but another
constant, or by crossing the not needed 4 bits in every byte during the
shift with additional operations.

I once did this bin -> bcd cinversion on a Z80 and it was very effective.

Reinhard Kirchner
Univ. Kaiserslautern, Germany
kirchner@uklirb.informatik.uni-kl.de