Re: LZ: manipulations

Subject: Re: LZ: manipulations
From: barrym <barrym@neosoft.com>
Date: Fri, 9 Aug 1996 07:48:15 -0500 (CDT)
In-Reply-To: <Pine.SOL.3.95.960808235519.10106A-100000@vertex.ucls.uchicago.edu>

On Thu, 8 Aug 1996, Will Stokes (3D Diamond productions) wrote:

> 
> 
> 				   wstokes@vertex.ucls.uchicago.edu
> 				   http://www.uic.edu/~hhstokes/index.html
> 				   Will Stokes
> 
> 
> quick and to the point, this is a dumb question I should already know the
> answer to but for some reason I don't.
> 
> other then adding registers can you:
> 
> multiply registers and values? how?

You need a routine for this on the Z80.  6 * 8 is 8 added 6 times.
6 * 8 is also 6 shifted left 3 times.  6 * 10 is 6 shifted left
3 times and then added to 6 shifted left once.  These are some
of the things you can use to write a routine to multiply.

> given register a=5 subtract a from 50 or some other number (50-a)? how?

  ld b,a
  ld a,50
  sub b

> any other manipulations (division) (a = -a) that i can do? How?

Division is the reverse of multiplication with the additional
complication of the remainder.  a = -a can be done with neg or
by subtracting from 0.

Barry

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