Welcome to the Datatron 205 and 220 Blog

This blog is a companion to T J Sawyer's Web Page that outlines the history of the Burroughs Datatron 205 and Paul Kimpel's incredible 205 and 220 emulators. Please visit those sites and return here to post any comments.

Monday, January 26, 2015

Prime Number Programs for the B205 Emulator

I put together two small prime number programs to exercise Paul's 205 emulator.  They utilize identical code to test the candidate numbers.  Prime numbers are those integers not evenly divisible by any smaller integer except 1.  These programs take the simple approach of attempting division by 3, 5, 7, 9, etc to see if the candidate is prime.  The program code for these can be found at the links under the heading, PROGRAMS FOR PAUL KIMPEL'S B205 EMULATOR just below the link to Paul's Emulator at the top right of this blog.

To run one of the programs, download and save to your computer the text file at the link.  Then,
  1. Start Paul's emulator
  2. Make sure the settings on the Supervisory Panel are set to "Normal" and "Step"
  3. Go to the Control Console.  Make sure that the Input switch is set to "Optical Reader"
  4. Press "CLEAR" and "CONT" -- the Paper Tape Reader will pop up on your screen
  5. Click Browse and navigate to the text file you saved.  Open it and the program will load and begin running.
  6. Click on the Flexowriter window to see the output
The  List of Prime Numbers program will immediately begin printing numbers on the Flexowriter. 

The Test a Number for Prime program will immediately stop after loading.  The Flexowriter has instructions for what to do next.  To keep the program as simple as possible, it lacks tests for 0, 1 and even numbers.  You may want to improve upon this, yourself.

You may also want to compare the speed of this program to one running at modern speed in your browser.  Try the one at this link.  It uses the same algorithm.

Perhaps some reader has saved an old paper tape or card deck with a copy of Tic-Tac-Toe or Three Pile Nim for the B205.  Please share it with us if you have!

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