The Apple-1 Software Library ^Beta

Also referred to as MicroChess, Micro-Chess or Micro Chess.

History

Initially this game was developed for the KIM-1, a single-board computer launched in 1976. In this same year, and being the result of six months of programming, Peter R. Jennings created a program that enabled a human to play chess against this machine.

At the end of 1976, the KIM-1 User Notes announced this chess-playing program running within 1K of memory. Peter Jennings writes on his website:

It was a program to bring the KIM-1 to life. Something to show friends and relatives that it was not just a toy, or a useless pile of wires and blinking LEDs, but a powerful computer, capable of playing chess.

A couple of months later Peter founded Micro-Ware Ltd and the game was ported to other micros like the Altair 8800, IMSAI 8080, TRS-80, Commodore PET, Sol 20 and the Apple ][. Eventually, several million copies were sold.

Porting

Home computer owners, like Larry Nelson, were marvelled at the game. He adapted the original KIM-1 version to make it work on his Apple-1. He stated in an interview:

A fellow named Peter Jennings wrote a chess-playing program for the KIM-1 computer, another 6502-based microcomputer. I sent off for a listing of his program and successfully adapted it to the Apple I.

At the time, Larry created a battle between two instances of Microchess, as mentioned here:

... on his Apple-1, and then used that computer to challenge the Micro-Chess program on his Radio Shack TRS-80. (As he recalls, the contest was a draw.)

In a recent e-mail conversation with Peter Jennings, he looks back at those days:

Although Micro-Ware did the porting to the TRS-80, Apple ][ etc, the Apple I port would have been done by an interested user based on the source code from the KIM-1 version. Instructions there were sufficient to make it run on any 6502 computer in its KIM-1 style. There were lots of home brew 6502 computers and some little known commercial ones. Owners of those computers would do their own ports and sometimes tell us about it or write it up in newsletters. Mostly they just did it and kept it to themselves.

Instructions

For beginners, learn how to play chess using this tutorial or read more about it here.

The chess board of Microchess uses a coordinate system, see the table below.

                  COMPUTER                        PIECE EXAMPLES
   ---------------------------------------
y | 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 |      
  |----+----+----+----+----+----+----+----+     WK = White King
A | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 |     WQ = White Queen
x |----+----+----+----+----+----+----+----+     WB = White Bishop
i | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 |
s |----+----+----+----+----+----+----+----+
  | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 |
  |----+----+----+----+----+----+----+----+
  | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 |
  |----+----+----+----+----+----+----+----+
  | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 |     BN = Black Knight
  |----+----+----+----+----+----+----+----+     BR = Black Rook
  | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 |     BP = Black Pawn
  |----+----+----+----+----+----+----+----+
  | 70 | 71 | 72 | 73 | 74 | 75 | 76 | 77 |
   --------------------------------------- 
                   PLAYER           x Axis

To make a move, a from and to coordinate has to be entered. The Computer plays at the top side. The pieces on the chess board are indicated by two letters: the first letter meaning Black or White, the second stands for its type. See above for examples.

Quick start

• Press 0 for normal level of play.
• Press RETURN for random opening and to not use default chess openings.
• Press G to start a new game, the chess board is being drawn with all pieces in their regular starting positions.
• Move a piece by using the coordinates (see table above) from yx and to yx followed by M.
  • For example, typing 6747M moves the right most Black Pawn two places forward.
  • The Computer acknowledges the move by printing it, like BP 67 47.
  • Press RETURN to tell the Computer to make a move.
• After some thinking, the board is redrawn and shows the moves of both the Player and the Computer. The move of the Computer is printed below the board, like WP 13 33.
• Player's turn, type in the move command again.

Options and commands

After the game starts, the level of play can be selected. Press 0 for Normal, 1 for Blitz or 2 for SuperBlitz. The higher the number, the lower the quality of the Computer's play and the quicker it will make a move.

Optionally, one of the chess openings can be selected by number 0-9. A chess opening consists of a fixed set of moves by the Black and White. Selecting an opening does not have effect on the initial setup of the pieces, these always have the normal starting position.

Note that when selecting the Computer to play Black, R has to be used to reverse sides before starting to play. Skip the use of a default opening by pressing RETURN, the Computer then plays a random opening.

Notice these commands are different from the ones listed in the original manual for the KIM-1 version of this game.

References

• History of Microchess by game author Peter Jennings on his website.
• KIM-1/6502 User Notes (November 1976, vol. 1, issue 2, p. 15) announces the first version of this game for the KIM-1.
• Original manual that came with the Microchess program for the KIM-1 computer. Its usage differs from the Apple-1 version.
• Publication of the game (ported to the Apple-1) by Larry Nelson on Applefritter.
• Interview with Larry Nelson (in Apple I Replica Creation, Back to the Garage by Tom Owad, chapter 1, p. 12), who ported the KIM-1 game to the Apple-1.
• Early Apple-1 user experiences, where Larry Nelson is mentioned.
• YouTube video showing an Apple-1 with Microchess 2 playing against ChatGPT.
• Microchess, Peter R. Jennings and the KIM-1 on Wikipedia.
• Chess and chess opening explained on Wikipedia.