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MEMPTR, esoteric register of the ZiLOG Z80 CPU.
by Boo-boo (first and draft English translation by Vladimir Kladov)

  As it is known, after the instruction BIT n,(HL) execution, bits 3 and 5 of the flag register become containing values that is not documented in the official documentation at all. Actually these bits are copied from the bits 11 and 13 of the internal register pair of Z80 CPU, which is used for 16-bit operations, and in most cases to handle addresses. This is usual practice for processors having 8-bits data bus working with 16-bits data.
  It is not known why and how these bits of the internal buffer register are copied to the flags register though. At least Sean Young in the "Undocumented Z80 Documented" refers to that phenomenon (http://www.myquest.nl/z80undocumented/) and a bit more info can be found in the Z80 description of another "nocash" project (http://www.work.de/nocash/zxdocs.htm) where such register pair is called as MEMPTR. Unfortunately until now attemts to crack the algorithm se

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Git submodules best practices

Useful commands

— Clone repository with submodules automatically:

git clone --recursive git@github.com:name/repo.git

— Initialize submodules after regular cloning:

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Some possible implementations of the Bresenham Algorithms in C.

The Bresenham line algorithm is an algorithm which determines which points in an
n-dimensional raster should be plotted in order to form a close approximation
to a straight line between two given points.
It is commonly used to draw lines on a computer screen, as it uses only integer
addition, subtraction and bit shifting, all of which are very cheap operations
in standard computer architectures.
It is one of the earliest algorithms developed in the field of computer graphics.
A minor extension to the original algorithm also deals with drawing circles.