README

8080_8086_XorShift For Pascal/MT+ Family of 8 and 16 bit compilers

A pre-compiled library for Pascal/MT+ with pure 8080 or 8088/6 asembler for use on CPM-80 and CPM-86

This code will produce with very little overhead and without the use of Floating point a Psudorandom number based off a seed of your choice. This is done useing the venerable XOR and Shift algorithm discovered by George Marsaglia.

You can read his paper here: http://www.jstatsoft.org/v08/i14/paper

Both of the versions were found to work on the V20-MBC2 in both 8080 and 8086 mode. There is nothing platform specific about any of the source and it should work well where the compiler can run and compile code (including but not limited to dos), while the system architecture is the same. Also note the pre-compiled relocatable files were generated under CP/M and CPM-86; you may need to recompile from source if you are having trouble linking them. the 8080 code was generated with M80.COM, and renaming the output extention to .ERL from .REL.

you can read about Fabios exellent V20-MBC Single board computer here:

https://hackaday.io/project/170924-v20-mbc-a-v20-8088-8080-cpu-homebrew-computer

UPDATE *** ADDED 8088/86 supprt for 16 bit Pascal/MT+ ***

thanks to Brad Forschingers helpfull blog post and example source:

http://b2d-f9r.blogspot.com/2010/08/16-bit-xorshift-rng.html

Usage and Notes:

To add to your program simply add {$I rand.def} after your declaration block and compile, then link RAND and XR86 or XR80. for 8080 the relocatable file is .erl and for 8086 it is .r86.

you can set the seed using various methods such as the system timer by calling the randomize procedure:

randomize([RANDOM SEED]);

note the seed must not be zero, you can asure this with a timer by simply adding 1.

and then retreve a random number by calling the function:

[some integer] := random([max number]);

this will return a random number from zero to (max number - 1).

Its important to note both the function and procedure use 16 bit 2's compliment integers for compatiblity, however the asm code uses a 16 bit word. This may slightly effect the distribution of the numbering (to a small or lage degree). in other words - this isn't sutable for research or cryptography; but most likely perfectly fine if you just need to seed a few random numbers for a game or whatnot.

NOTE: the asembler code automatically handles the entry points within the context of pascal/mt+ if you wish to use this with another compiled language that uses microsofts relocateable file format you will need to consult that compilers manual and update the code for working with your specific compiler.

MIT License

Copyright (c) 2021 Dave Collins

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

I can Be reached at Z80dad (at) gmail (dot) com.