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| From | D Finnigan <dog_cow@macgui.com> |
| Newsgroups | comp.sys.apple2.programmer |
| Subject | Re: Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz |
| Date | Mon, 12 Jan 2015 18:39:23 +0000 (UTC) |
| Organization | Mac GUI |
| Lines | 40 |
| Message-ID | <dog_cow-1421087988@macgui.com> (permalink) |
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wssimms wrote: > Am Montag, 12. Januar 2015 13:03:06 UTC-5 schrieb D Finnigan: >> This routine came up in a discussion in comp.sys.apple2 in November. >> >> It was published on pages 52 and 53 of the the Winter 1980 edition of The >> Apple Orchard Magazine. Following is my summary of the article and the >> source listing. >> >> >> Binary-to-Decimal Shortcut >> (Small is Beautiful) >> >> by Steve Wozniak >> > > This seems like the most obvious way to do a binary to decimal conversion > on the 6502, but I like the Woz-optimization (Woztimization?) of doing a > ROL in the high byte of the result instead of another round of ADC/STA. > Furthermore, in this article, Woz goes on to say: The algorithm works as follows. The first bit shifted out of the binary argument carries a weight of 2 to the 15th. It is added to the result which is subsequently doubled 15 times (in decimal), restoring the proper weight component. Each bit is treated in this manner. The high-order result byte, DEC2, can be shifted left at step (3) instead of added to itself in decimal since it will not exceed 9 ($FFFF = 06 55 35). If this is done, DEC2 need not be initialized to zero, since the original contents will be shifted out during execution. This optimization is implemented in the following 6502 subroutine [listed in my initial article - DF]. -- ]DF$ Apple II Book: http://macgui.com/newa2guide/ Usenet: http://macgui.com/usenet/ <-- get posts by email! Apple II Web & Blog hosting: http://a2hq.com/
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Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz D Finnigan <dog_cow@macgui.com> - 2015-01-12 18:02 +0000
Re: Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz wssimms@gmail.com - 2015-01-12 10:22 -0800
Re: Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz D Finnigan <dog_cow@macgui.com> - 2015-01-12 18:39 +0000
Re: Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz jbrooks@blueshiftinc.com - 2015-09-25 21:12 -0700
Re: Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz qkumba <peter.ferrie@gmail.com> - 2015-10-02 08:27 -0700
Re: Binary-to-Decimal Conversion Subroutine 27-Apr-80 Woz John Brooks <jbrooks@blueshiftinc.com> - 2015-10-03 08:31 -0700
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