Casio fx-8000G Chess

Written by dr. Samir Ribić, Sarajevo, Bosnia and Herzegovina, 25. Aug 2014

In 1990 I typed in my first Chess program for Casio fx-8000G. However, I was aware of the limitations that the machine had. The language (let's call it FGL, shortcut of Wikipedia's First Generation Language) was very slow, so it could not go in depth. The algorithm was: look all available moves (except castling and e.p.) and take the best capture or closest field to the center, then (only on level 2) look all the opponent counter moves, and if you lose more than you gain try the next move. It took about 5 minutes thinking per move and about 1 minute to draw the board, because there was no Unplot command. I called this chess Stupido chess, but I promised to myself, one day I will make better chess program. I knew it was possible, ZX-81 had 1K chess, but it was written in then unavailable for casio fx-8000G machine code.

This day is here. H.G.Muller wrote the smallest chess program in C (about 1800 bytes), called Micro-Max, which still knows all the rules (including castling, en passant and pawn promotion), uses alpha-beta search with move ordering heuristics and evaluates material, position and pawn structure. Piotr Piatek discovered machine code programming. So, I manually translated Micro-Max chess to upd1007 assembly language, added graphical presentation, modified some parameters to fit into Casio low memory and processing power, removed transposition tables, converted program to maximal usage of registers. So this chess typically processes about 100-5000 positions in 3-100 seconds per move, and depending on position it can think up to 8 half moves in depth.

How to play? Use the arrow keys to select the piece and press Range. Now move the cursor to the destination field and press Range again. When you want that the calculator makes a move, press Graph. Press AC for leave the program. This simple approach allows you to play Man vs. Computer, Computer vs. Human, Human vs. Human, Computer vs. Computer or matches where Computer temporary replaces Human player.

The program takes about 1870 bytes. Together with startup code, it fills up the complete file editor, and uses graphic printer buffer for recursion, leaving Program editor area intact.

CHESS screen shot

To enter CHESS follow the procedure:

Entering unprotected mode

Press the reset button.
Mode 2
Should give 1446 bytes free
Mode 1

Press Range

    Xmin -10
      max 10
     scl 1
     Ymin -10
      max 10
     scl 1

Press G↔T

Press Range

    Xmin -10
      max 10
     scl 0
     Ymin -10
      max 10
     scl 0

Press G↔T
Now press AC, then Shift and Alpha and type
SAVE "A"G
There should be a space between SAVE and the quote sign, but not between the second quote sign and G.
Press EXE
You will get SYS error
Press left arrow and EXE to repeat the last command
Now the message will be Save executing I/O error
Again left arrow and EXE to repeat the last command
Now the message will be again SYS error
Now press AC and go to mode 3 (PCL). You will see two occupied programs (4 and 5). Delete the program 4 using AC. Now all programs are occupied. Press SHIFT DEL to delete all the programs.
Free memory is now 1654 bytes. The array indexes are no longer controlled.

Entering hex loader

The easiest way to enter machine code is to plot it in video memory
Switch to Comp mode (Mode +)
Switch to WRT mode (Mode 2)
Select Prog 0

Enter the following program

  Ans→B
  S<2⇒Goto 0
  0→M
  0.3594→A[42]
  1.00419048E41→A[43]~A[44]
  1.00419848E41→A[45]
  1.0007705E41→A[46]
  Lbl 0
  S=0⇒Goto 1
  Range 1,95,0,1,63,0
  Cls
  8→C
  Lbl 3
  " "
  Dsz C
  Goto 3
  11→A
  Lbl 1
  53→C
  32→D
  B<0⇒B+2xy32→B
  Lbl 2
  Frac .5B=0⇒Plot A,C
  Frac .5B≠0⇒Isz M
  Int .5B→B
  Isz C
  C=57⇒49→C
  Frac ((D-1)÷8)=0⇒Dsz A
  Dsz D
  Goto 2
  A+8→A
  0→S
  Plot 0,0

Exit from editor switching to WRT mode (Mode 2)
Select Prog 2

Enter the following program

        (˗5÷9)×(1E˗44)→Z[356]~Z[358]

Exit from editor switching to RUN mode (Mode 1)

Entering the program itself

Video memory is only temporary place for the program, due to limited size and screen garble.
The program is normally executed from address &h4000. We need to split it to multiple chunks stored to video memory together with routines that will transfer them to their final place in file editor.
Switch to Base-N (Mode -)
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 1

2→S
Hex
423FFF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
FF4046AA:Prog 0
41472B42:Prog 0
CC006000:Prog 0
0841C800:Prog 0
56920856:Prog 0
83805789:Prog 0
4060452A:Prog 0
5C8041FB:Prog 0
815E82E0:Prog 0
FB835E84:Prog 0
205D85C0:Prog 0
5C87605E:Prog 0
90085E91:Prog 0
02604510:Prog 0
60405060:Prog 0
451D5695:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 228 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 1 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 2

2→S
Hex
42403F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
0960459A:Prog 0
23912074:Prog 0
40160792:Prog 0
18704016:Prog 0
40CC0142:Prog 0
472C9900:Prog 0
E0991020:Prog 0
4D0A1B89:Prog 0
41FBB5FB:Prog 0
B1FBB2FB:Prog 0
925E93E0:Prog 0
FBB754B5:Prog 0
030AB501:Prog 0
2311037F:Prog 0
40805EB7:Prog 0
017040B3:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 247 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 2 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 3

2→S
Hex
42407F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
2B900874:Prog 0
40B32396:Prog 0
FE7440B3:Prog 0
5EB70123:Prog 0
82047F40:Prog 0
9B2BB504:Prog 0
7740B354:Prog 0
B1C154B2:Prog 0
E1049777:Prog 0
5EB5022B:Prog 0
93E07440:Prog 0
B35EC10A:Prog 0
88C1442B:Prog 0
B7007C44:Prog 0
F754B103:Prog 0
5CB4035C:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 263 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 3 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 4

2→S
Hex
4240BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
A70354B2:Prog 0
0304B080:Prog 0
5CB70356:Prog 0
B0012335:Prog 0
037F40DC:Prog 0
FB925E93:Prog 0
E07040E8:Prog 0
5485035C:Prog 0
92035486:Prog 0
035C9303:Prog 0
128941A0:Prog 0
A7035CA5:Prog 0
03040003:Prog 0
7C44A454:Prog 0
A50304B0:Prog 0
075CA603:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 233 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 4 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 5

2→S
Hex
4240FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
5CA00302:Prog 0
B0105CC0:Prog 0
03A2C003:Prog 0
03B0015C:Prog 0
A30356B0:Prog 0
02232603:Prog 0
7F41262C:Prog 0
A0807C41:Prog 0
26E82070:Prog 0
41310AA3:Prog 0
01A2A303:Prog 0
E0305CA0:Prog 0
032BA000:Prog 0
7C44A454:Prog 0
A7035CB0:Prog 0
035EA280:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 215 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 5 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 6

2→S
Hex
42413F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
5EA1802B:Prog 0
B7007C41:Prog 0
5554B203:Prog 0
0737035C:Prog 0
B0037041:Prog 0
5B54A003:Prog 0
0A300354:Prog 0
B0035CB3:Prog 0
032CB088:Prog 0
7444A12B:Prog 0
87807C41:Prog 0
99A08703:Prog 0
23B0007C:Prog 0
419954B0:Prog 0
03030703:Prog 0
03B00224:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 225 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 6 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 7

2→S
Hex
42417F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
B0807C41:Prog 0
99548703:Prog 0
03300303:Prog 0
B00224B0:Prog 0
807C4199:Prog 0
FB925E93:Prog 0
202BA603:Prog 0
7F41AB54:Prog 0
B0032307:Prog 0
037441AB:Prog 0
0FB310A0:Prog 0
B3035CA4:Prog 0
03F3B154:Prog 0
B0030327:Prog 0
0304B007:Prog 0
7C41C256:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 240 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 7 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 8

2→S
Hex
4241BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
B101FBC0:Prog 0
2BA4007C:Prog 0
41CD5EC0:Prog 0
01034023:Prog 0
FBC02BA6:Prog 0
037F41DB:Prog 0
5EC0010C:Prog 0
402354A4:Prog 0
03040003:Prog 0
0E400374:Prog 0
44A154A4:Prog 0
0304B007:Prog 0
5CC00342:Prog 0
4744A2C0:Prog 0
035C9603:Prog 0
42474CA2:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 222 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 8 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 9

2→S
Hex
4241FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
C0035C97:Prog 0
0342472C:Prog 0
2C97807C:Prog 0
4213FB92:Prog 0
5E932054:Prog 0
92635493:Prog 0
83130383:Prog 0
24B4807C:Prog 0
44B354B5:Prog 0
035CB603:Prog 0
54B00323:Prog 0
10037C42:Prog 0
340BB601:Prog 0
2BB6007C:Prog 0
44045F9C:Prog 0
A0F3B52B:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 250 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 9 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 10

2→S
Hex
42423F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
A6067F42:Prog 0
6354A703:Prog 0
02B0085C:Prog 0
C003A0C0:Prog 0
831A14A3:Prog 0
54B00302:Prog 0
B0085CC0:Prog 0
03A0C083:Prog 0
1B14A3F3:Prog 0
B080A103:Prog 0
80B30380:Prog 0
A70354A5:Prog 0
0306B020:Prog 0
80B00354:Prog 0
A10304B0:Prog 0
8874428C:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 211 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 10 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 11

2→S
Hex
42427F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
54800302:Prog 0
B00680A2:Prog 0
031A9CBE:Prog 0
2BA6037F:Prog 0
42F156B4:Prog 0
0AF3B554:Prog 0
A70303B0:Prog 0
025CC003:Prog 0
04B08874:Prog 0
42AFA0C0:Prog 0
03032503:Prog 0
7C42B21B:Prog 0
14A354A7:Prog 0
0302B002:Prog 0
5CC00304:Prog 0
B0887442:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 228 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 11 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 12

2→S
Hex
4242BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
CAA0C003:Prog 0
0325037C:Prog 0
42CD1B14:Prog 0
A31A14A3:Prog 0
54B00302:Prog 0
200302B0:Prog 0
0104B080:Prog 0
7C42F1A0:Prog 0
B00306B0:Prog 0
0780B003:Prog 0
56B68456:Prog 0
B7031A16:Prog 0
E3549223:Prog 0
54934313:Prog 0
01437C43:Prog 0
1224B280:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 221 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 12 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 13

2→S
Hex
4242FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
74431255:Prog 0
9263E102:Prog 0
635CC043:Prog 0
5CC16370:Prog 0
431E5581:Prog 0
43E10143:Prog 0
5CC0235C:Prog 0
C1436045:Prog 0
100F8018:Prog 0
558383E1:Prog 0
03835C81:Prog 0
635C8283:Prog 0
54C0035C:Prog 0
830354C1:Prog 0
035C8403:Prog 0
5494A354:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 233 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 13 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 14

2→S
Hex
42433F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
95C31A05:Prog 0
C35496A3:Prog 0
5497C31A:Prog 0
05C3E905:Prog 0
C054A203:Prog 0
5C870354:Prog 0
B0035C90:Prog 0
0354B603:Prog 0
5C910360:Prog 0
40506045:Prog 0
1D5C9401:Prog 0
5C9521E9:Prog 0
14A02396:Prog 0
FE7C43B2:Prog 0
2B95E07C:Prog 0
43AC2B27:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 250 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 14 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 15

2→S
Hex
42437F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
C17443AC:Prog 0
2B30E174:Prog 0
43AC2B90:Prog 0
087443AC:Prog 0
5485C354:Prog 0
86E31216:Prog 0
E3E106E3:Prog 0
9737C0B3:Prog 0
05C054A2:Prog 0
60548301:Prog 0
54842158:Prog 0
9F1340BB:Prog 0
14A05480:Prog 0
0302B006:Prog 0
80A103F3:Prog 0
B080A203:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 236 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 15 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 16

2→S
Hex
4243BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
80B00354:Prog 0
A50380A7:Prog 0
0354A403:Prog 0
80B30354:Prog 0
94435495:Prog 0
63131263:Prog 0
7C43F924:Prog 0
B3807443:Prog 0
F99F1580:Prog 0
BB126054:Prog 0
A7035CB1:Prog 0
0356B080:Prog 0
04220306:Prog 0
30035CB2:Prog 0
032BB700:Prog 0
7C4404FB:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 239 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 16 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 17

2→S
Hex
4243FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
B7704137:Prog 0
56B00223:Prog 0
26037F44:Prog 0
6C54A323:Prog 0
03B10754:Prog 0
A64303B2:Prog 0
035CC023:Prog 0
0E40432B:Prog 0
C0007444:Prog 0
6E54A703:Prog 0
02B00354:Prog 0
A023F631:Prog 0
04B1075C:Prog 0
A1030F21:Prog 0
23A0A103:Prog 0
03000303:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 230 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 17 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 18

2→S
Hex
42443F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
B0065CC0:Prog 0
032BC000:Prog 0
74446E54:Prog 0
A10307B0:Prog 0
015CC103:Prog 0
A0C12354:Prog 0
A10307B0:Prog 0
025CC103:Prog 0
A0C1435C:Prog 0
C0230E40:Prog 0
4370446E:Prog 0
FBC054A5:Prog 0
0304B020:Prog 0
06400354:Prog 0
A7230220:Prog 0
23033023:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 211 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 18 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 19

2→S
Hex
42447F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
5CC0030E:Prog 0
40237C44:Prog 0
952BA605:Prog 0
7F449B0A:Prog 0
A4017044:Prog 0
9B54B003:Prog 0
5CA2032B:Prog 0
A4007C41:Prog 0
43704112:Prog 0
0AA7090C:Prog 0
A77754A7:Prog 0
03033403:Prog 0
7440EB2B:Prog 0
931F7744:Prog 0
C22B93E2:Prog 0
7F44C25E:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 251 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 19 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 20

2→S
Hex
4244BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
B5622B93:Prog 0
E07444F4:Prog 0
6045100F:Prog 0
8018FB81:Prog 0
5E82E0FB:Prog 0
835E8420:Prog 0
FB85FB86:Prog 0
5E87805E:Prog 0
90805E91:Prog 0
01604050:Prog 0
60451D5C:Prog 0
92015C93:Prog 0
21E91260:Prog 0
70406C54:Prog 0
92A35493:Prog 0
C31305C3:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 247 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 20 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 21

2→S
Hex
4244FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
24B6807C:Prog 0
45091A9A:Prog 0
61549201:Prog 0
54932158:Prog 0
9900E099:Prog 0
10E09920:Prog 0
E09930E0:Prog 0
58BD3700:Prog 0
BD2700BD:Prog 0
1700BD07:Prog 0
0058579E:Prog 0
E9569544:Prog 0
FB870495:Prog 0
7760459A:Prog 0
F8075EB3:Prog 0
021BBA61:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 254 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 21 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 22

2→S
Hex
42453F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
7C453259:Prog 0
C0FE4077:Prog 0
0000FE40:Prog 0
774583FE:Prog 0
40774587:Prog 0
FE407745:Prog 0
77FE4077:Prog 0
457DFE40:Prog 0
77456BFE:Prog 0
40774571:Prog 0
70453D03:Prog 0
95107045:Prog 0
32029510:Prog 0
70453203:Prog 0
95017045:Prog 0
32029501:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 266 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 22 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 23

2→S
Hex
42457F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
70453256:Prog 0
96FE585C:Prog 0
B1A12396:Prog 0
09744596:Prog 0
54B1C170:Prog 0
453254B1:Prog 0
E1589772:Prog 0
009F7200:Prog 0
405A8041:Prog 0
5D80600F:Prog 0
9940CC01:Prog 0
415A905E:Prog 0
8108F394:Prog 0
FB86C900:Prog 0
5E8208A8:Prog 0
032B06A1:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 243 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 23 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 24

2→S
Hex
4245BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
7445CC2B:Prog 0
87007445:Prog 0
CC5E8308:Prog 0
0C830F74:Prog 0
45D50A03:Prog 0
81EC83EC:Prog 0
83EC8342:Prog 0
462B0794:Prog 0
015E8408:Prog 0
A2836123:Prog 0
06C17445:Prog 0
F5239509:Prog 0
7C45F5F0:Prog 0
1381134A:Prog 0
010B8401:Prog 0
7445E40A:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 244 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 24 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 25

2→S
Hex
4245FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
86010B82:Prog 0
017445BB:Prog 0
07940148:Prog 0
08491F0A:Prog 0
86080B81:Prog 0
017445B6:Prog 0
0CD23F97:Prog 0
07006006:Prog 0
20B300E0:Prog 0
BB7040B3:Prog 0
704058EF:Prog 0
EFEFEFEF:Prog 0
EFEF0000:Prog 0
00000000:Prog 0
000000EF:Prog 0
AFAC28AC:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 235 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 25 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 26

2→S
Hex
42463F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
AFEF00EF:Prog 0
2E2A202A:Prog 0
2EEF00EC:Prog 0
A8A12020:Prog 0
28EF00EF:Prog 0
AC2A2028:Prog 0
ACEF00EF:Prog 0
A92C282C:Prog 0
A9EF00EB:Prog 0
282E282E:Prog 0
28EB0018:Prog 0
18181818:Prog 0
181818EF:Prog 0
AFAC2AAC:Prog 0
AFEF0000:Prog 0
E72400E7:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 256 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 26 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 27

2→S
Hex
42467F40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
02E700EF:Prog 0
2EAAA0AA:Prog 0
2EEF00EC:Prog 0
AAA524A7:Prog 0
28EF00EF:Prog 0
AC2B272B:Prog 0
ACEF00EF:Prog 0
A92CA92C:Prog 0
A9EF00EB:Prog 0
28AEA8AE:Prog 0
28EB0016:Prog 0
14151713:Prog 0
1514161C:Prog 0
15100D0C:Prog 0
0D101512:Prog 0
12121212:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 257 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 27 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 28

2→S
Hex
4246BF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
12121216:Prog 0
0F0A0908:Prog 0
070A0F00:Prog 0
00000000:Prog 0
00000012:Prog 0
0B060302:Prog 0
03060B00:Prog 0
00000000:Prog 0
00000010:Prog 0
09040100:Prog 0
01040900:Prog 0
00000000:Prog 0
00000010:Prog 0
09040100:Prog 0
01040900:Prog 0
00000000:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 104 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 28 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 29

2→S
Hex
4246FF40:Prog 0
5AF7415B:Prog 0
37600008:Prog 0
70000000:Prog 0
00000012:Prog 0
0B060302:Prog 0
03060B09:Prog 0
09090909:Prog 0
09090916:Prog 0
0F0A0908:Prog 0
070A0F0E:Prog 0
0C0D0F0B:Prog 0
0D0C0E1C:Prog 0
15100D0C:Prog 0
0D101500:Prog 0
F0F1EF00:Prog 0
01100001:Prog 0
100F1100:Prog 0
0E121F21:Prog 0
00080007:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 181 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 29 into the file editor.
Switch to WRT mode (Mode 2)
Select Prog 1

Enter the following program, part 30

2→S
Hex
42473F40:Prog 0
5AF7415B:Prog 0
34600008:Prog 0
70000000:Prog 0
0C090407:Prog 0
006464FE:Prog 0
2C2CF484:Prog 0
000000FE:Prog 0
01010103:Prog 0
00704001:Prog 0
47554755:Prog 0
47554755:Prog 0
47203A30:Prog 0
EC3A5D38:Prog 0
35335B5A:Prog 0
0E5D3033:Prog 0
34875B5A:Prog 0
01434D00:Prog 0
53534548:Prog 0
43000000:Prog 0
Dec
M◿

Exit from editor switching to RUN mode (Mode 1)
Start Prog 1 and wait until plotting stops
If displayed number is not 222 edit again Prog 1 and check the hex codes carefully, repair the error, and start it again.
Start Prog 2 to transfer chunk no 30 into the file editor.
Testing the game and cleaning up unnecessary programs
Go to File editor (Mode 0). You should notice a new password protected program CHESS there.
Go to RUN mode (Mode 1)
Execute Prog "CHESS"
If the program is started, congratulations!
If the program is not started, it seems that you skipped some chunk, or that some entry errror was undetected by checksum. Enter the programs again
Go to Mode PCL (Mode 3)
Press Shift Del to clear program editor area, because hex loader is no longer required.

Source-object listing

This is commented assembly listing along with instruction opcodes that are entered into Prog 1

0000:            ORG    &h4000  
4000: FF         DB &hFF    ; This byte is not excuted, it is file editor EOF marker (backwards)
4001:           
4001:           CHESSSTART:
4001: 4046AA            LDW IX,BOARD-1     ; Initialized board will be relocated to printer screen buffer
4004: 41472B            LDW IY,STEPVECS-1
4007: 42CC00            LDW IZ,&hCC01-1    ; Here will be the board
400A: 600008            CAL &h0008         ; Relocate routine
400D: 41C800     LDW IY,&hC800  ; StackPos=0 in memory for large screen buffer
4010: 569208     LD R74,8  ; GameSide=8 for White, 16 for Black
4013:           ; LDM R64..R71,0  ; Initialise some global variables
4013: 568380     ld R67,128
4016:           ; R72..R73,0  ; FunctionValue=0
4016:           ; R69..R70 ; RootEval=0
4016:           ; LDM R69..R70,0
4016:           ; R65..R66,0  ; N=0
4016:           ; R67   ; RootEp
4016:           LEVEL EQU 4
4016:            
4016:           LP:         ; do {                 Main game loop
4016: 578940     LDM R65..R66,0  ; N=0
4019:           
4019: 60452A     CAL ENTERMOVE      ; Display board and return variables InputFrom and InputTo after Graph is pressed or Range twice
401C:            ; Now prepare parameters to call main search routine
401C: 5C8041     LD R0,R74    ;                      Side=GameSide;
401F: FB81       BYD R1            ;           Alpha=-INF;
4021: 5E82E0     LD R2,&hE0              
4024: FB83       BYD R3             ;                    Beta=INF;
4026: 5E8420     LD R4,&h20     
4029: 5D85C0     LDM R5..R6,R69..R70 ;               Eval=RootEval;
402C: 5C8760     LD R7,R67 ;                         epSqr=RootEp;
402F: 5E9008     LD R8,8  ;                          LastTo=8; 8 is illegal square, this value indicates root of search tree
4032: 5E9102     LD R9,2 ;                          Depth=2;
4035:            
4035: 604510     CAL SAVEALL     ;                   SaveAll();
4038:           
4038: 604050     CAL SEARCH  ;                           Search();
403B:           
403B: 60451D     CAL RESTALL ;                           RestoreAll(); 
403E:           
403E: 569509     LD R77,9  ;Cursor out of board
4041: 60459A     CAL DISP
4044:              ; For the move entered on keyboard, we will return Beta, it will remain INF (&h2000) if we are not in check, and the move is valid
4044:              
4044:               ;            if (FunctionValue==INF) GameSide ^= 24;     Move is legal, flip GameSide between 8 and 16
4044: 239120     TSB R73,&h20
4047: 744016     JMP NZ,LP   ; Invalid move
404A: 079218     XR R74,&h18
404D: 704016     JMP LP  ; } while (1);
4050:           ; db 0 ; accidentally one jump has FF in it
4050:           SEARCH:
4050: 40CC01     LDW IX,&hCC01        ;  IX points to Board
4053: 42472C     LDW IZ,STEPVECS      ;  IZ points to StepVecs
4056: 9900E0     STM +(IY),R0..R7     ; Store parameter in  registers to memory , IY is stack for local variables
4059: 991020     STM +(IY),R8..R9
405C: 4D0A       SBW IY,10            
405E:           ;    Alpha--;
405E: 1B8941     SBM R1..R2,1
4061:           ;    IterDepth = BestFrom = BestTo = 0;
4061: FBB5       BYD R29
4063: FBB1       BYD R25
4065: FBB2       BYD R26
4067:            
4067:           ;    BestScore=-INF;
4067: FB92       BYD R10
4069: 5E93E0     LD R11,&hE0     ;        
406C:           ; Completely stupid full-width search in principle tries anything, even the most idiotic moves like taking a defended Pawn with a Queen. 
406C:           ;  Going into the search 'depth first', on the other hand, tends to dive deep into idiotic variations before realizing they were idiotic, 
406C:           ; when accidentally hitting upon the proper refutation. 
406C:           ;while( 1) {          Iterative deeping loop
406C:           ITDLOOP:
406C:           ;       h=0;   Variable h will be zero if we need to exit iterative deeping loop
406C: FBB7       BYD R31
406E:           ;       if (IterDepth++ < Depth)           Depth below 2 half moves     
406E: 54B503     LD R88,R29
4071: 0AB501     AD R29,1
4074: 231103     TSB R88,R9
4077: 7F4080     JMP NC,ITDDELSE
407A:           ;         h=1;
407A: 5EB701     LD R31,1
407D: 7040B3     JMP ITDENDIF
4080:           ITDDELSE:
4080:           ;       else
4080:           ;       if   (LastTo==8 & InputFrom==0xFE) {         We are at thinked move, root of search
4080: 2B9008     TSB R8,8
4083: 7440B3     JMP NZ,ITDENDIF
4086: 2396FE     TSB R78,&hFE
4089: 7440B3     JMP NZ,ITDENDIF
408C:           
408C:           ;        h=1;      
408C: 5EB701     LD R31,1
408F:           ;        if (!(N<2048 & IterDepth<4)) {  // Increasing these constants will make the game smarter, but much slower. Do not increase IterDepth above 12, due to allocated stack space   
408F: 238204     TSB R66,LEVEL  ; 4 * 256 positions to check
4092: 7F409B     JMP NC,SETIT
4095: 2BB504     TSB R29,LEVEL  ; 4 half moves depth
4098: 7740B3     JMP C,ITDENDIF
409B:           SETIT: 
409B:           ;          InputFrom=BestFrom;    // So, we are at root, thinked move and exhausted limit of moves or iteration depth. Set up the best move as it was entered
409B: 54B1C1     LD R78,R25
409E:           ;          InputTo=BestTo&~M;
409E: 54B2E1     LD R79,R26
40A1: 049777     AN R79,&h77
40A4:           ;          IterDepth=2;
40A4: 5EB502     LD R29,2
40A7:           ;          if (BestScore==-INF)   
40A7:           ;            printf ("Check mate\n");
40A7: 2B93E0     TSB R11,&hE0   ; Write by putting Sprite CM
40AA: 7440B3     JMP NZ,ITDENDIF
40AD: 5EC10A     LD R33,10
40B0: 88C144     ST (IX+&h44),R33
40B3:           ;        }
40B3:           ;       }
40B3:           ITDENDIF: 
40B3:           ;       if (! h) 
40B3:           ;          break;        Exit the iterative deeping root
40B3: 2BB700      TSB R31,0
40B6: 7C44F7      JMP Z,ENDITDLOOP   
40B9:           ;/* Each iteration consist of a move-generation run, immediately searching      */
40B9:           ;    /* all moves as they are generated. The best move from the previous iter-      */
40B9:           ;    /* ation (still contained in BestFrom, BestTo) is slipped in front, though.    */
40B9:           ;    /* To make this easier, move generation starts at StartSqr = BestFrom.         */
40B9:           ;    /* The highest -bit of BestTo indicates if there is a valid best move to try.         */  
40B9:           ;        FromSqr = StartSqr = BestFrom;    Start from previous best move
40B9: 54B103      LD R88,R25
40BC: 5CB403      LD R28,R88
40BF: 5CA703      LD R23,R88
40C2:           ;        h = BestTo & S;   
40C2: 54B203      LD R88,R26
40C5: 04B080      AN R88,128
40C8: 5CB703      LD R31,R88
40CB:           ;        if (IterDepth > 1)   /* unconsidered:static eval */
40CB: 56B001      LD R88,1
40CE: 233503      TSB R88,R29
40D1: 7F40DC      JMP NC,IFITELSE
40D4:           ;            BestScore = -INF;
40D4: FB92        BYD R10
40D6: 5E93E0      LD R11,&hE0  
40D9: 7040E8      JMP ENDIFIT
40DC:           ;        else
40DC:           IFITELSE:
40DC:           ;            BestScore = Eval;
40DC: 548503      LD R88,R5
40DF: 5C9203      LD R10,R88
40E2: 548603      LD R88,R6
40E5: 5C9303      LD R11,R88
40E8:           
40E8:           ENDIFIT:
40E8:           ;        N=N+1;    /* node count (for timing)  */
40E8: 128941      ADM R65..R66,1
40EB:           ;        do {
40EB:           MAINDO:
40EB:           ;            Piece = Board[FromSqr];   /* scan board looking for  piece */
40EB: A0A703      LD R88,(IX+R23)
40EE: 5CA503      LD R21,R88
40F1:           ;            if (Piece & Side) {  /*  This players piece */
40F1: 040003      AN R88,R0
40F4: 7C44A4      JMP Z,ENDPCSIDE
40F7:           ;                StepVec = PieceType = Piece & 7;   /* set StepVec > 0          */
40F7: 54A503      LD R88,R21
40FA: 04B007      AN R88,7
40FD: 5CA603      LD R22,R88
4100: 5CA003      LD R16,R88
4103:           ;                j = StepVecs[PieceType + 16];  /* first step vector Piece  */ -1 to avoid FF in file editor
4103: 02B010      AD R88,16
4106: 5CC003      LD R32,R88
4109: A2C003      LD R88,(IZ+R32)
410C: 03B001      SB R88,1
410F: 5CA303      LD R19,R88
4112:           ;                while (1) {
4112:           DIRLOOP:
4112:           
4112:           ;                    if (PieceType > 2 & StepVec < 0)    /* loop over directions o[] */
4112: 56B002      LD R88,2
4115: 232603      TSB R88,R22
4118: 7F4126      JMP NC,BIDIRECT
411B: 2CA080      TAN R16,128
411E: 7C4126      JMP Z,BIDIRECT
4121:           
4121:           ;                      StepVec = -StepVec;
4121: E820        CMP R16
4123: 704131      JMP ENDBIDIR
4126:           ;                    else 
4126:           BIDIRECT:
4126:           ;                      StepVec = -StepVecs[++j]; 
4126: 0AA301      AD R19,1
4129: A2A303      LD R88,(IZ+R19)
412C: E030        CMP R88
412E: 5CA003      LD R16,R88
4131:           ENDBIDIR:
4131:           ;                    if (StepVec == 0)
4131:           ;                      break;
4131: 2BA000      TSB R16,0
4134: 7C44A4      JMP Z,ENDDIRLOOP
4137:           ;                    A:   /* resume normal after best */
4137:           RESUMENORMAL:
4137:           ;                     ToSqr = FromSqr;
4137:           ;           /* For each direction we scan ToSqr along the ray startig at FromSqr.    */
4137:           
4137: 54A703      LD R88,R23
413A: 5CB003      LD R24,R88
413D:           ;                    SkipSqr = RookSqr = S;   /* S = 0x80 = dummy square  */
413D: 5EA280      LD r18,128
4140: 5EA180      ld r17,128
4143:           ;                    do {
4143:           ;            /* FromSqr, ToSqr here scan through all tentative moves. If there      */
4143:           ;            /* is an old best move to try first, this is indicated in the 8-bit    */
4143:           ;            /* of BestTo (which was copied from the S-bit), and we overrule the    */
4143:           ;            /* generated ToSqr (which might ly at other distance or in direction)  */
4143:           ;            /* We then test if ToSqr is on the board, if we have an e.p. capture,  */
4143:           ;            /* are blocked by an own piece, and if Pawn moves are valid.           */
4143:           
4143:           DOCAPT:
4143:           ;                        if (h != 0)
4143: 2BB700      TSB R31,0
4146: 7C4155      JMP Z,SETNEWTO
4149:           ;                            ToSqr = BestTo ^ h;    /* sneak-in prev. best move */
4149: 54B203      LD R88,R26
414C: 073703      XR R88,R31
414F: 5CB003      LD R24,R88
4152: 70415B      JMP SETCAPTSQR
4155:           ;                        else
4155:           SETNEWTO:
4155:           ;                            ToSqr += StepVec;
4155: 54A003      LD R88,R16
4158: 0A3003      AD R24,R88
415B:           SETCAPTSQR:
415B:           ;                        CaptSqr = ToSqr;
415B: 54B003      LD R88,R24
415E: 5CB303      LD R27,R88
4161:           ;                        if (ToSqr & M) break;  /* board edge hit (M=0x88)  */
4161: 2CB088      TAN R24,&h88
4164: 7444A1      JMP NZ,ENDDOCAPT
4167:           ; We can not castle if in check, or fields that we pass with king are attacked
4167:           ;                        if ((epSqr - S && Board[epSqr] && ToSqr - epSqr < 2 & epSqr - ToSqr < 2))
4167: 2B8780      TSB R7,128
416A: 7C4199      JMP Z,CHECKENPAS
416D: A08703      LD R88,(IX+R7)
4170: 23B000      TSB R88,0
4173: 7C4199      JMP Z,CHECKENPAS
4176: 54B003      LD R88,R24
4179: 030703      SB R88,R7
417C: 03B002      SB R88,2
417F: 24B080      TAN R88,128
4182: 7C4199      JMP Z,CHECKENPAS
4185: 548703      LD R88,R7
4188: 033003      SB R88,R24
418B: 03B002      SB R88,2
418E: 24B080      TAN R88,128
4191: 7C4199      JMP Z,CHECKENPAS
4194:           ;                            BestScore = INF; /* castling-on-Pawn-check bug fixed */
4194: FB92        BYD R10
4196: 5E9320      LD R11,&h20
4199:           CHECKENPAS:
4199:           ;                        if (PieceType < 3 & ToSqr == epSqr)  /* shift CaptSqr if e.p.    */
4199: 2BA603      TSB R22,3
419C: 7F41AB      JMP NC,SETVICTIM
419F: 54B003      LD R88,R24
41A2: 230703      TSB R88,R7
41A5: 7441AB      JMP NZ,SETVICTIM
41A8:           ;                            CaptSqr ^= 16;
41A8: 0FB310      XR R27,16
41AB:           SETVICTIM:
41AB:           ;                        Victim = Board[CaptSqr];  Take piece we capture
41AB: A0B303      LD R88,(IX+R27)
41AE: 5CA403      LD R20,R88
41B1:           ;                        if (Victim & Side                                                    /* capture own              */
41B1:           ;                                  | PieceType < 3 & !(ToSqr - FromSqr & 7) - !Victim)      /* bad pawn move              */
41B1: F3B1        BYD R89
41B3: 54B003      LD R88,R24   ; ToSqr
41B6: 032703      SB R88,R23   ; From Sqr
41B9: 04B007      AN R88,7
41BC: 7C41C2      JMP Z,SV1
41BF: 56B101      LD R89,1
41C2:           SV1:
41C2: FBC0        BYD R32
41C4: 2BA400      TSB R20,0
41C7: 7C41CD      JMP Z,SV2
41CA: 5EC001      LD R32,1
41CD:           SV2:
41CD: 034023      SB R89,R32
41D0: FBC0        BYD R32
41D2: 2BA603      TSB R22,3
41D5: 7F41DB      JMP NC,SV3
41D8: 5EC001      LD R32,1
41DB:           SV3:
41DB: 0C4023      AN R32,R89
41DE: 54A403      LD R88,R20
41E1: 040003      AN R88,R0
41E4: 0E4003      OR R32,R88  
41E7:           ;                            break;
41E7: 7444A1      JMP NZ,ENDDOCAPT
41EA:           ;                        i = PieceVal[Victim & 7];    /* value of victim piece.16 bit    */
41EA: 54A403     LD R88,R20
41ED: 04B007     AN R88,7
41F0: 5CC003     LD R32,R88
41F3: 424744     LDW IZ,PIECEVAL
41F6: A2C003     LD R88,(IZ+R32)
41F9: 5C9603     LD R14,R88
41FC: 42474C     LDW IZ,PIECEVALHI
41FF: A2C003     LD R88,(IZ+R32)
4202: 5C9703     LD R15,R88
4205: 42472C     LDW IZ,STEPVECS
4208:           ;                        if (i < 0)     /* King capture gives maximal score   */
4208: 2C9780     TAN R15,128
420B: 7C4213     JMP Z,TESTCUT
420E:           ;                        BestScore = INF          ; /* castling-on-Pawn-check bug fixed */
420E: FB92       BYD R10
4210: 5E9320     LD R11,&h20     ;        
4213:           
4213:           TESTCUT:
4213:           ;                        if (BestScore >= Beta)    /* abort on fail high       */
4213: 549263     LD R91,R10
4216: 549383     LD R92,R11
4219: 130383     SBM R91..R92,R3..R4
421C: 24B480     TAN R92,128
421F:            
421F:           ;                            goto CutOff;
421F: 7C44B3     JMP Z,CUTOFF  
4222:           ;            /* We now have a move to search. If there is depth left, we different- */
4222:           ;            /* ially update the evaluation, Make the move, Search it recursively   */
4222:           ;            /* UnMake it, and update the best score & move. If not, we ignore it.  */
4222:           
4222:           TEST:
4222:           ;                        if (s = IterDepth - (ToSqr != LastTo)) {    /* remaining depth(-recapt.)*/
4222: 54B503     LD R88,R29
4225: 5CB603     LD R30,R88
4228: 54B003     LD  R88,R24
422B: 231003     TSB R88,R8
422E: 7C4234     JMP Z,SETITDEP
4231: 0BB601     SB R30,1
4234:           
4234:           SETITDEP:
4234: 2BB600     TSB R30,0
4237: 7C4404     JMP Z,ENDSCOREIF
423A:           ;                            if (PieceType < 6)     /* center positional pts.   */
423A: 5F9CA0     LDM R12..R13,0
423D: F3B5       BYD R93
423F: 2BA606     TSB R22,6
4242: 7F4263     JMP NC,STARTMOVE
4245:           ;                                Score = Board[FromSqr + 8] - Board[ToSqr + 8];
4245: 54A703     LD R88,R23
4248: 02B008     AD R88,8
424B: 5CC003     LD R32,R88
424E: A0C083     LD R92,(IX+R32)
4251: 1A14A3     ADM R12..R13,R92..R93
4254: 54B003     LD R88,R24
4257: 02B008     AD R88,8
425A: 5CC003     LD R32,R88
425D: A0C083     LD R92,(IX+R32)
4260: 1B14A3     SBM R12..R13,R92..R93
4263:           
4263:           ;                            else
4263:           ;                                Score = 0;
4263:           
4263:           STARTMOVE
4263:           ;              /* Make move & evaluate                                              */
4263:           
4263:           ;                            Board[RookSqr] = Board[CaptSqr] = Board[FromSqr] = 0;
4263: F3B0       BYD R88
4265: 80A103     ST (IX+R17),R88
4268: 80B303     ST (IX+R27),R88
426B: 80A703     ST (IX+R23),R88
426E:           
426E:           ;                            Board[ToSqr] = Piece | 32;  /* do move, set non-virgin bit (Piece moved)*/
426E: 54A503     LD R88,R21
4271: 06B020     OR R88,32
4274: 80B003     ST (IX+R24),R88
4277:           ;                            if (!(RookSqr & M))  /* castling */
4277: 54A103     LD R88,R17
427A: 04B088     AN R88,&h88
427D: 74428C     JMP NZ,TESTPAWN
4280:           ;                                Board[SkipSqr] = Side + 6, Score += 30;   Put Rook and Score
4280:           
4280: 548003     LD R88,R0
4283: 02B006     AD R88,6
4286: 80A203     ST (IX+R18),R88
4289: 1A9CBE     ADM R12..R13,30
428C:           TESTPAWN:
428C:           ;                            if (PieceType < 3) {   /* pawns:                   */
428C: 2BA603     TSB R22,3
428F: 7F42F1     JMP NC,SETNEWBETA
4292:           ;                                Score -= 9 * ((FromSqr - 2 & M || Board[FromSqr - 2] - Piece) +  /* structure, undefended    */
4292:           ;                                    (FromSqr + 2 & M || Board[FromSqr + 2] - Piece) - 1); /* squares plus bias */
4292: 56B40A     LD R92,10
4295: F3B5       BYD R93
4297: 54A703     LD R88,R23
429A: 03B002     SB R88,2
429D: 5CC003     LD R32,R88
42A0: 04B088     AN R88,&h88
42A3: 7442AF     JMP NZ,PAWNPUNIS1
42A6: A0C003     LD R88,(IX+R32)
42A9: 032503     SB R88,R21
42AC: 7C42B2     JMP Z,PAWNCHECK2
42AF:           PAWNPUNIS1:
42AF: 1B14A3     SBM R12..R13,R92..R93
42B2:           PAWNCHECK2
42B2: 54A703     LD R88,R23
42B5: 02B002     AD R88,2
42B8: 5CC003     LD R32,R88
42BB: 04B088     AN R88,&h88
42BE: 7442CA     JMP NZ,PAWNPUNIS2
42C1: A0C003     LD R88,(IX+R32)
42C4: 032503     SB R88,R21
42C7: 7C42CD     JMP Z,PAWNAWARD
42CA:           PAWNPUNIS2:
42CA: 1B14A3     SBM R12..R13,R92..R93
42CD:           PAWNAWARD:
42CD: 1A14A3     ADM R12..R13,R92..R93
42D0:           
42D0:           ;                                if (ToSqr + StepVec + 1 & S)   /* promote Pawn  */
42D0: 54B003     LD R88,R24
42D3: 022003     AD R88,R16
42D6: 02B001     AD R88,1
42D9: 04B080     AN R88,128
42DC: 7C42F1     JMP Z,SETNEWBETA
42DF:           ;                                    Board[ToSqr] |= 7, i += 800;   /* promote Pawn to Queen,  update score */
42DF: A0B003     LD R88,(IX+R24)
42E2: 06B007     OR R88,7
42E5: 80B003     ST (IX+R24),R88
42E8: 56B684     LD R94,&h84
42EB: 56B703     LD R95,3
42EE: 1A16E3     ADM R14..R15,R94..R95
42F1:           
42F1:           ;                            }
42F1:           ; Now recursive call of Eval function to calculate value of reply
42F1:           ; Set new Beta value to -MAX(BestScore,Alpha)
42F1:           SETNEWBETA:
42F1:           ;                            if (BestScore > Alpha)
42F1: 549223     LD R89,R10
42F4: 549343     LD R90,R11
42F7: 130143     SBM R89..R90,R1..R2
42FA: 7C4312     JMP Z,NEWALP1
42FD: 24B280     TAN R90,128
4300: 744312     JMP NZ,NEWALP1
4303:           ;                                NewBeta = -BestScore;
4303: 559263     LDM R90..R91,R10..R11
4306: E10263     CMPM R90..R91
4309: 5CC043     LD R32,R90
430C: 5CC163     LD R33,R91
430F: 70431E     JMP REPLYEVAL
4312:           
4312:           ;                            else NewBeta = -Alpha;
4312:           NEWALP1:
4312: 558143     LDM R89..R90,R1..R2
4315: E10143     CMPM R89..R90
4318: 5CC023     LD R32,R89
431B: 5CC143     LD R33,R90
431E:           
431E:           ; //                           Score = -Search(24 - Side, -Beta, NewBeta, -Eval - Score - i, SkipSqr, ToSqr, s);
431E:           REPLYEVAL:
431E:           ;                       if (StackPos < 24*32) {
431E:           ; TSB r121,&hCB             IY Stack checking
431E:           ; JMP NC,REPLYFINISH
431E:           ;                            SaveAll();   All local variables to IY stack
431E: 604510       CAL SAVEALL
4321:           ;                            Side=24-Side;  Flip side
4321: 0F8018       XR R0,24
4324:           ;                            Alpha=-Beta;
4324:           
4324: 558383     LDM R91..R92,R3..R4
4327: E10383     CMPM R91..R92 
432A: 5C8163     LD R1,R91
432D: 5C8283     LD R2,R92
4330:           ;                            Beta=NewBeta;
4330: 54C003     LD R88,R32
4333: 5C8303     LD R3,R88
4336: 54C103     LD R88,R33
4339: 5C8403     LD R4,R88
433C:           ;                            Eval=(-Eval-Score-i);  /* New Eval                 */
433C: 5494A3     LD R93,R12
433F: 5495C3     LD R94,R13
4342: 1A05C3     ADM R5..R6,R93..R94
4345: 5496A3     LD R93,R14
4348: 5497C3     LD R94,R15
434B: 1A05C3     ADM R5..R6,R93..R94
434E: E905C0     CMPM R5..R6
4351:            
4351:           ;                            epSqr=SkipSqr;  /* New en passant square */
4351: 54A203     LD R88,R18
4354: 5C8703     LD R7,R88
4357:           ;                            LastTo=ToSqr;
4357: 54B003     LD R88,R24
435A: 5C9003     LD R8,R88
435D:           ;                            Depth=s;
435D: 54B603     LD R88,R30
4360: 5C9103     LD R9,R88
4363:           
4363:           ;                            Search();  Recursion
4363: 604050     CAL SEARCH
4366:           ;                            RestoreAll();  Back from IY stack
4366: 60451D     CAL RESTALL
4369:           ;                            Score= -FunctionValue;   Oponent reply is negative
4369: 5C9401     LD R12,R72
436C: 5C9521     LD R13,R73
436F: E914A0     CMPM R12..R13
4372:           ;                        }
4372:           REPLYFINISH:
4372:           ;              /* If the Search routine was called as move-legality checker, we     */
4372:           ;              /* now return before unmaking the move if it was the input move.     */
4372:           
4372:           ;                            if (InputFrom != 0xFE)    Here we are if we entered the move, recursion was used for legality check
4372: 2396FE     TSB R78,&hFE
4375: 7C43B2     JMP Z,TAKEBACK
4378:           ;                                if (Score + INF && FromSqr == InputFrom & ToSqr == InputTo & LastTo == 8) {  // Move found
4378: 2B95E0     TSB R13,&hE0
437B: 7C43AC     JMP Z,ALTENTERSC
437E: 2B27C1     TSB R23,R78
4381: 7443AC     JMP NZ,ALTENTERSC
4384: 2B30E1     TSB R24,R79
4387: 7443AC     JMP NZ,ALTENTERSC
438A: 2B9008     TSB R8,8
438D: 7443AC     JMP NZ,ALTENTERSC
4390:           
4390:            
4390:           ;                                    RootEval = -Eval - i;   /* update eval, material    */
4390: 5485C3     LD R94,R5
4393: 5486E3     LD R95,R6
4396: 1216E3     ADM R94..R95,R14..R15
4399: E106E3     CMPM R94..R95
439C: 9737C0     STM -(SP),R95..R94
439F: B305C0     LDM R69..R70,(SP)+
43A2:           ;                                    RootEp = SkipSqr;
43A2: 54A260     LD R67,R18
43A5:           ;                                    if (Board[ToSqr] - Piece & 7 && P - InBuf > 5)
43A5:           ;                                        Board[ToSqr] -= InBuf[4] & 3; /* under-promotions */
43A5:           ; NOT IMPLEMENTED
43A5:           ;                                    FunctionValue=Beta;  /* Not in check signal    */
43A5: 548301     LD R72,R3
43A8: 548421     LD R73,R4
43AB:           ;                                    return;
43AB: 58         RTN
43AC:           ;                                }
43AC:           ALTENTERSC:
43AC:           ;                                Score = BestScore;   /* (prevent fail-lows on    K-capt. replies)       */
43AC: 9F1340      STM -(SP),R11..R10
43AF: BB14A0      LDM R12..R13,(SP)+
43B2:           
43B2:           ;                            }
43B2:           TAKEBACK:
43B2:           ;  undo move,RookSqr can be dummy
43B2:           ;                            Board[RookSqr] = Side + 6;
43B2: 548003     LD R88,R0
43B5: 02B006     AD R88,6
43B8: 80A103     ST (IX+R17),R88
43BB:           ;                            Board[SkipSqr] = Board[ToSqr] = 0;
43BB: F3B0       BYD R88
43BD: 80A203     ST (IX+R18),R88
43C0: 80B003     ST (IX+R24),R88
43C3:           ;                            Board[FromSqr] = Piece;
43C3: 54A503     LD R88,R21
43C6: 80A703     ST (IX+R23),R88
43C9:           
43C9:           ;                            Board[CaptSqr] = Victim;
43C9: 54A403     LD R88,R20
43CC: 80B303     ST (IX+R27),R88
43CF:           
43CF:            ;             /* Process score. If the move just searched was a previous best      */
43CF:           ;              /* move that was tried first, we take its Score and redo the first   */
43CF:           ;              /* ray of this piece. Otherwise update best score and move.          */
43CF:           
43CF:            
43CF:           ;                            if (Score > BestScore)
43CF: 549443     LD R90,R12
43D2: 549563     LD R91,R13
43D5: 131263     SBM R90..R91,R10..R11
43D8: 7C43F9     JMP Z,TESTH
43DB: 24B380     TAN R91,128
43DE: 7443F9     JMP NZ,TESTH
43E1:           
43E1:           ;                                BestScore = Score, BestFrom = FromSqr, BestTo = ToSqr | S & SkipSqr;   /* Update and mark non-castling with S  */
43E1: 9F1580      STM -(SP),R13..R12
43E4: BB1260      LDM R10..R11,(SP)+
43E7: 54A703      LD R88,R23
43EA: 5CB103      LD R25,R88
43ED: 56B080      LD R88,128
43F0: 042203      AN R88,R18
43F3: 063003      OR R88,R24
43F6: 5CB203      LD R26,R88
43F9:           
43F9:           
43F9:           TESTH:
43F9:           ;                            if (h) {
43F9: 2BB700     TSB R31,0
43FC: 7C4404     JMP Z,ENDSCOREIF
43FF:            
43FF:           ;                                h = 0;
43FF: FBB7       BYD R31
4401:           ;                                goto A;    Best is first done, now normal search
4401: 704137     JMP RESUMENORMAL
4404:           ;                            }
4404:           ;                        }
4404:           ENDSCOREIF:
4404:           ;            /* Determine if we have to continue scanning this ray. We must stop    */
4404:           ;            /* on a capture, or if the piece is a non-slider, with the exceptions  */
4404:           ;            /* of double moves for Pawns and King (castlings!). Such double moves  */
4404:           ;            /* cause setting of the SkipSqr, that otherwise is equal to the dummy S*/
4404:           ;                        if(PieceType>2) {
4404: 56B002     LD R88,2
4407: 232603     TSB R88,R22
440A: 7F446C     JMP NC,NOPCM
440D:           ;                          PieceMask=PieceType-3|j-7 ;  /* King moving sideways,          */
440D: 54A323     LD R89,R19
4410: 03B107     SB R89,7
4413: 54A643     LD R90,R22
4416: 03B203     SB R90,3
4419: 5CC023     LD R32,R89
441C: 0E4043     OR R32,R90
441F:           ;                          if (! PieceMask) {
441F: 2BC000     TSB R32,0
4422: 74446E     JMP NZ,RAYDECIDE
4425:           ;                            RookSqr=FromSqr+3^StepVec>>1&7; /* virgin Rook in corner     */
4425: 54A703     LD R88,R23
4428: 02B003     AD R88,3
442B: 54A023     LD R89,R16
442E:            ;LD R90,r16
442E:            ;BIU R90
442E: F631       ROD R89
4430: 04B107     AN R89,7
4433: 5CA103     LD r17,R88
4436: 0F2123     XR R17,R89
4439:           ;                            PieceMask=Board[RookSqr]-Side-6;  /* virgin Rook in corner     */
4439: A0A103     LD R88,(IX+R17)
443C: 030003     SB R88,R0
443F: 03B006     SB R88,6
4442: 5CC003     LD R32,R88
4445:           ;                            if (! PieceMask)
4445: 2BC000     TSB R32,0
4448: 74446E     JMP NZ,RAYDECIDE
444B:           ;                              PieceMask= Board[RookSqr^1]|Board[RookSqr^2];  /* 2 empty sqrs. next to R */
444B: 54A103     LD R88,R17
444E: 07B001     XR R88,1
4451: 5CC103     LD R33,R88
4454: A0C123     LD R89,(IX+R33)
4457: 54A103     LD R88,R17
445A: 07B002     XR R88,2
445D: 5CC103     LD R33,R88
4460: A0C143     LD R90,(IX+R33)
4463: 5CC023     LD R32,R89
4466: 0E4043     OR R32,R90
4469: 70446E     JMP RAYDECIDE
446C:           ;                          }
446C:           ;                         }
446C:           ;                         else
446C:           NOPCM: 
446C:           ;                           PieceMask=0;
446C: FBC0       BYD R32
446E:           
446E:           RAYDECIDE
446E:           ;                          if(FromSqr+StepVec-ToSqr|Piece&32|PieceMask ) 
446E: 54A503     LD R88,R21
4471: 04B020     AN R88,32
4474: 064003     OR R88,R32
4477: 54A723     LD R89,R23
447A: 022023     AD R89,R16
447D: 033023     SB R89,R24
4480: 5CC003     LD R32,R88
4483: 0E4023     OR R32,R89
4486: 7C4495     JMP Z,SETSKIP
4489:           ;                           Victim+=PieceType<5;  /* fake capt. for nonsliding pieces */  
4489: 2BA605     TSB R22,5
448C: 7F449B     JMP NC,ENDSETSKIP
448F: 0AA401     AD R20,1
4492: 70449B     JMP ENDSETSKIP
4495:           ;                        else  
4495:           SETSKIP:
4495:           ;                           SkipSqr=ToSqr;       /* enable e.p. */
4495: 54B003     LD R88,R24
4498: 5CA203     LD R18,R88
449B:           ENDSETSKIP:
449B:           ;                       }while(!Victim);   /* if not capt. continue ray */ 
449B: 2BA400     TSB R20,0
449E: 7C4143     JMP Z,DOCAPT
44A1:           ENDDOCAPT:
44A1:           ;                    
44A1:           ;                }
44A1: 704112     JMP DIRLOOP
44A4:           ENDDIRLOOP:
44A4:           ;            }
44A4:           ENDPCSIDE:
44A4:           ;        } while ((FromSqr = FromSqr + 9 & ~M) - StartSqr); /* next sqr. of board, wrap  */
44A4: 0AA709     AD R23,9
44A7: 0CA777     AN R23,&h77
44AA: 54A703     LD R88,R23
44AD: 033403     SB R88,R28
44B0: 7440EB     JMP NZ,MAINDO
44B3:           ; /* All moves have been searched; wrap up iteration by testing for check- or    */
44B3:           ;    /* stalemate, which leave Score at -INF. Call Search with Depth=1 after null   */
44B3:           ;    /* move to determine if we are in check. Finally store result in hash.         */
44B3:            
44B3:           ;        CutOff:
44B3:           CUTOFF:
44B3:           ;            if (BestScore > INF - M | BestScore < M - INF)
44B3: 2B931F     TSB R11,&h1F
44B6: 7744C2     JMP C,VERLEGAL
44B9: 2B93E2     TSB R11,&hE2
44BC: 7F44C2     JMP NC,VERLEGAL
44BF:           
44BF:           FORCEITEREND:
44BF:           ;                IterDepth = 98;
44BF: 5EB562     LD R29,98
44C2:           VERLEGAL
44C2:           ;        if (BestScore == -INF) {
44C2: 2B93E0     TSB R11,&hE0
44C5: 7444F4     JMP NZ,FINISHED
44C8:           
44C8:           ;//            BestScore = -Search(24 - Side, -INF, INF, 0, S, S, 1);
44C8:           
44C8:           
44C8:           ;                            SaveAll();
44C8: 604510     CAL SAVEALL
44CB:           ;                            Side=24-Side;
44CB: 0F8018     XR R0,24
44CE:           ;                            Alpha=-INF;
44CE: FB81       BYD R1
44D0: 5E82E0     LD R2,&hE0
44D3:           ;                            Beta=INF;
44D3: FB83       BYD R3
44D5: 5E8420     LD R4,&h20
44D8:           ;                            Eval=0;
44D8: FB85       BYD R5
44DA: FB86       BYD R6
44DC:           ;                            epSqr=S;
44DC: 5E8780     LD R7,128
44DF:           ;                            LastTo=S;
44DF: 5E9080     LD R8,128
44E2:           ;                            Depth=1;
44E2: 5E9101     LD R9,1
44E5:           ;                            Search();
44E5: 604050     CAL SEARCH
44E8:           ;                            RestoreAll();
44E8: 60451D     CAL RESTALL
44EB:           ;                            BestScore= -FunctionValue;
44EB: 5C9201     LD R10,R72
44EE: 5C9321     LD R11,R73
44F1: E91260     CMPM R10..R11
44F4:           
44F4:           ;        }
44F4:           FINISHED:
44F4:           ;        if (LastTo == 8) printf("%2d ply, %9d searched, %6d by (%2x,%2x)\n",
44F4:           ;            IterDepth - 1, N, BestScore, BestFrom, BestTo & 0x77);
44F4:           ;    }
44F4: 70406C     JMP ITDLOOP
44F7:           ENDITDLOOP:
44F7:           ;    BestScore += BestScore < Eval;   /* faster-gain award     */
44F7: 5492A3     LD R93,R10
44FA: 5493C3     LD R94,R11
44FD: 1305C3     SBM R93..R94,R5..R6
4500: 24B680     TAN R94,128
4503: 7C4509     JMP Z,SETFVAL
4506:           
4506: 1A9A61     ADM R10..R11,1
4509:           ;    FunctionValue=BestScore;
4509:           SETFVAL:
4509: 549201      LD R72,R10
450C: 549321      LD R73,R11
450F:           ENDSEARCH:
450F:           ;    return;
450F: 58         RTN
4510:            
4510:           ; THESE TWO SUBROUTINES SAVE AND RESTORE LOCAL VARIABLES 
4510:            
4510:            
4510:           SAVEALL:                      ; Save all registers representing local variables
4510: 9900E0     STM +(IY),R0..R7
4513: 9910E0     STM +(IY),R8..R15
4516: 9920E0     STM +(IY),R16..R23
4519: 9930E0     STM +(IY),R24..R31
451C: 58         RTN
451D:           RESTALL:                     ; Restore all registers representing local variables 
451D: BD3700     LDM R31..R24,(IY)-
4520: BD2700     LDM R23..R16,(IY)-
4523: BD1700     LDM R15..R8,(IY)-
4526: BD0700     LDM R7..R0,(IY)-
4529: 58         RTN
452A:            
452A:           ; USER INTERFACE, CHECK KEYBOARD AND DISPLAY BOARD 
452A:            
452A:           ENTERMOVE
452A: 579EE9     LDM R78..R79,&h9    ; Initially no move selected
452D: 569544     LD R77,&h44 ; Cursor to center
4530: FB87       BYD R7  ; Flash flag for cursor
4532:           DRAWBOARD:
4532: 049577     AN R77,&h77  ; Wrap cursor if out of board
4535: 60459A     CAL DISP   ; Display the board
4538: F807       INV R7    ; Flip the cursor flag
453A: 5EB302     LD R27,2   ; Small loop of 512 passes
453D:           DELAY1:
453D: 1BBA61      SBM R26..R27,1
4540: 7C4532      JMP Z,DRAWBOARD
4543:           
4543: 59C0       GST R32,KI   ; READ KEYBOARD and shift bits to determine keys
4545: FE40       ROD R32
4547: 770000     JMP C,0
454A: FE40       ROD R32
454C: 774583     JMP C,COMPMOVE
454F: FE40       ROD R32
4551: 774587     JMP C,SETFROMTO
4554: FE40       ROD R32
4556: 774577     JMP C,LEFTKEY
4559: FE40       ROD R32
455B: 77457D     JMP C,RIGHTKEY
455E: FE40       ROD R32
4560: 77456B     JMP C,UPKEY
4563: FE40       ROD R32
4565: 774571     JMP C,DOWNKEY
4568: 70453D     JMP DELAY1
456B:           ; Update cursor for each case  
456B:             
456B:           UPKEY:
456B: 039510      SB R77,16
456E: 704532      JMP DRAWBOARD
4571:           DOWNKEY:
4571: 029510      AD R77,16
4574: 704532      JMP DRAWBOARD
4577:           LEFTKEY:
4577: 039501      SB R77,1
457A: 704532      JMP DRAWBOARD
457D:           RIGHTKEY:
457D: 029501      AD R77,1
4580: 704532      JMP DRAWBOARD
4583:           COMPMOVE:  ; Graph key, computer moves
4583: 5696FE      LD R78,&hFE  
4586: 58          RTN
4587:           SETFROMTO:  ; Disp key human moves
4587: 5CB1A1      LD R25,R77
458A: 239609      TSB R78,9   ; From field selected
458D: 744596      JMP NZ,SETTO
4590: 54B1C1      LD R78,R25  
4593: 704532      JMP DRAWBOARD
4596:           SETTO:
4596: 54B1E1      LD R79,R25  ; To field selected
4599: 58          RTN
459A:           DISP:
459A: 977200      stm   -(sp),r122..r120  ; Save index registers
459D: 9F7200      stm   -(sp),r58..r56
45A0:             
45A0:           
45A0: 405A80     LDW IX,&h5A80 ; Start of video memory, clear screen routine
45A3: 415D80     LDW IY,&h5A80+768
45A6: 600F99     cal    &h0F99
45A9: 40CC01     LDW IX,&hCC01  ; IX points to Board
45AC: 415A90     LDW IY,&h5A80+16  ; IY points to video memory, centered board
45AF:           ; LD R5,&hEF
45AF: 5E8108     LD R1,8  ; Row loop counter
45B2: F394       BYD R76
45B4: FB86       BYD R6  ; tested position
45B6:           BRDLP:
45B6: C900       ST +(IY),0  ; First vertical column
45B8: 5E8208     LD R2,8  ; Piece loop counter
45BB:           BRDPIELP:
45BB: A803       LD R3,(IX)+  ; Take piece from board
45BD: 2B06A1     TSB R6,R77  ; Check if position is cursor
45C0: 7445CC     JMP NZ,IGNOREFLAGS  ; if not do not flash
45C3: 2B8700     TSB R7,0             ; Test flash phase on/off
45C6: 7445CC     JMP NZ,IGNOREFLAGS  ; if not do not flash
45C9:           
45C9: 5E8308     LD R3,8  ; This field will be black square
45CC:           IGNOREFLAGS:
45CC: 0C830F     AN R3,&h0F  ; We ignore upper nibble of piece
45CF: 7445D5     JMP NZ,FNDPSPRITE
45D2: 0A0381     AD R3,R76  ; Blank field will be interchanged as black/white
45D5:           FNDPSPRITE:  ; Piece value will be multiplied by 8
45D5: EC83       BIU R3
45D7: EC83       BIU R3
45D9: EC83       BIU R3
45DB: 42462B     LDW IZ,EMPTYFIELD  ; Set address of piece sprites
45DE: 079401     XR R76,1       ;  Black/White field
45E1:           ; Sprite loop
45E1: 5E8408     LD R4,8
45E4:           PCLOOP:
45E4: A28361     LD R75,(IZ+R3) ; Take column of piece of field sprite
45E7: 2306C1     TSB R78,R6     ; If the field was previously selected, invert
45EA: 7445F5     JMP NZ,COPYPIECE
45ED: 239509     TSB R77,9
45F0: 7C45F5     JMP Z,COPYPIECE
45F3:           
45F3:           
45F3: F013       INV R75   ; Invert
45F5:           COPYPIECE:
45F5: 8113       ST +(IY),R75  ; Put the sprite column
45F7: 4A01       ADW IZ,1   ; move pointer to sprites
45F9: 0B8401     SB R4,1
45FC: 7445E4     JMP NZ,PCLOOP  ;  repeat sprite loop
45FF: 0A8601     AD R6,1    ; increase current postiion
4602:           ; XR R5,&hEF
4602: 0B8201     SB R2,1
4605: 7445BB     JMP NZ,BRDPIELP  ; End piece loop
4608:           ; XR R5,&hEF
4608: 079401     XR R76,1  ; Next row starts with oposite field color
460B: 4808       ADW IX,8  ; Next row in board
460D: 491F       ADW IY,31 ; Next row in video memory
460F: 0A8608     AD R6,8   ; increase current position to next row
4612: 0B8101     SB R1,1
4615: 7445B6     JMP NZ,BRDLP
4618: 0CD23F     AN R42,&h3F  ; PARAMETER DO REFRESH
461B:           
461B: 970700     stm -(sp),r71..r64    ; Save global variables
461E: 600620     CAL &h0620   ; SYSTEM CALL REFRESH
4621: B300E0     ldm r64..r71,(sp)+   ; Restore global variables
4624:           
4624: BB7040     ldm    r56..r58,(sp)+   ; Restore index registers
4627: B37040     ldm    r120..r122,(sp)+
462A:           
462A: 58         RTN
462B:            
462B:           ; Here are Piece screen definitions  
462B:            
462B: EFEFEFEFEFEFEF00
                EMPTYFIELD: DB &hEF,&hEF,&hEF,&hEF,&hEF,&hEF,&hEF,&h00
4633: 0000000000000000
                BLACKFIELD: DB &h00,&h00,&h00,&h00,&h00,&h00,&h00,&h00
463B: EFAFAC28ACAFEF00
                BLKPAWN:    DB &hEF,&hAF,&hAC,&h28,&hAC,&hAF,&hEF,&h00
4643: EF2E2A202A2EEF00
                BLKKING:    DB &hEF,&h2E,&h2A,&h20,&h2A,&h2E,&hEF,&h00
464B: ECA8A1202028EF00
                BLKKNIGHT:  DB &hEC,&hA8,&hA1,&h20,&h20,&h28,&hEF,&h00
4653: EFAC2A2028ACEF00
                BLKBISHOP:  DB &hEF,&hAC,&h2A,&h20,&h28,&hAC,&hEF,&h00
465B: EFA92C282CA9EF00
                BLKROOK:    DB &hEF,&hA9,&h2C,&h28,&h2C,&hA9,&hEF,&h00
4663: EB282E282E28EB00
                BLKQUEEN:   DB &hEB,&h28,&h2E,&h28,&h2E,&h28,&hEB,&h00
466B: 1818181818181818
                CURSOR:     DB &h18,&h18,&h18,&h18,&h18,&h18,&h18,&h18
4673: EFAFAC2AACAFEF00
                WHTPAWN:    DB &hEF,&hAF,&hAC,&h2A,&hAC,&hAF,&hEF,&h00
467B: 00E72400E702E700
                UNKNOWN3:   DB &h00,&hE7,&h24,&h00,&hE7,&h02,&he7,&h00
4683: EF2EAAA0AA2EEF00
                WHTKING:    DB &hEF,&h2E,&hAA,&hA0,&hAA,&h2E,&hEF,&h00
468B: ECAAA524A728EF00
                WHTKNIGHT:  DB &hEC,&hAA,&hA5,&h24,&hA7,&h28,&hEF,&h00
4693: EFAC2B272BACEF00
                WHTBISHOP:  DB &hEF,&hAC,&h2B,&h27,&h2B,&hAC,&hEF,&h00
469B: EFA92CA92CA9EF00
                WHTROOK:    DB &hEF,&hA9,&h2C,&hA9,&h2C,&hA9,&hEF,&h00
46A3: EB28AEA8AE28EB00
                WHTQUEEN:   DB &hEB,&h28,&hAE,&hA8,&hAE,&h28,&hEB,&h00
46AB:           ; BOARD left half is actual board, right half is field value. To check field legality binary AND the value with &h88
46AB: 16141517131514161C15100D0C0D1015
                BOARD:     DB 22 ,20,21,23,19,21,20,22,  28,21,16,13,12,13,16,21
46BB: 1212121212121212160F0A0908070A0F
                           DB 18 ,18,18,18,18,18,18,18,  22,15,10, 9, 8, 7,10,15
46CB: 0000000000000000120B06030203060B
                           DB  0, 0, 0, 0, 0, 0, 0, 0,   18,11, 6, 3, 2, 3, 6,11
46DB: 00000000000000001009040100010409
                           DB  0, 0, 0, 0, 0, 0, 0, 0,   16, 9, 4, 1, 0, 1, 4, 9
46EB: 00000000000000001009040100010409
                           DB  0, 0, 0, 0, 0, 0, 0, 0,   16, 9, 4, 1, 0, 1, 4, 9
46FB: 0000000000000000120B06030203060B
                           DB  0, 0, 0, 0, 0, 0, 0, 0,   18,11, 6, 3, 2, 3, 6,11
470B: 0909090909090909160F0A0908070A0F
                           DB  9, 9, 9, 9, 9, 9, 9, 9,   22,15,10, 9, 8, 7,10,15
471B: 0E0C0D0F0B0D0C0E1C15100D0C0D101500
                           DB 14,12,13,15,11,13,12,14,   28,21,16,13,12,13,16,21,0
472C:           
472C: F0F1EF0001100001100F11000E121F2100
                STEPVECS   DB  -16, -15, -17, 0, 1, 16, 0, 1, 16, 15, 17, 0, 14, 18, 31, 33, 0 ; /* step-vector lists */
473D: 0800070C090407
                           DB 7+1, -1+1, 6+1, 11+1, 8+1, 3+1, 6+1  ; /* 1st dir. in StepVecs[] per piece*/
4744: 006464FE2C2CF484
                PIECEVAL   DB 0, 100, 100, -2,  44,  44, 244, 132 ; Absolute piece values low bytw   */
474C: 000000FE01010103
                PIECEVALHI DB 0,   0,   0, -2,   1,   1,   1, 3   ; High byte
4754:                              
4754:           
4754:             ORG &h4755
4755: 704001      JMP CHESSSTART
4758: 4755475547554755
                  db 'GUGUGUGU' ; This sequence is also 4755475547554755
4760: 47203A30EC3A5D3835335B5A0E5D303334875B5A01
                  DB 'G :0',&hEC,':]853[Z',&h0E,']034',&h87,'[Z',01
4775: 434D00      DB 'CM',00  ; PASSWORD 2 LETTERS
4778: 5353454843
                  DB 'SSEHC'  ; Name 5 letters
477D:           
477D:           
477D:           
477D:

Source listing of relocators

This is commented assembly listing of the routines executed inside video memory which transfer programs from video memory to the file editor memory.

5AE8: 423FFF LDW IZ,&H3FFF ; destination address-1
5AEB: 405AF7 LDW IX,&H5AF7 ; source address in video memory-1
5AEE: 415B37 LDW IY,&H5B37 ; end of source in video memory
5AF1: 600008 CAL 8 ; transfer block
5AF4: 700000 JMP 0 ; home screen
5AF7: 00 DB 0 ; address needs to be divisible by 4
5AF8: FF4046 db &hFF,&h40,&h46 ; chess program part
...

Files to download

chess.zip

List of files in the archive:

chess.asm - source text
chess.bin - assembled binary file
ssehc.bin - the above file backwards, to be transferred to the calculator through a serial interface
ram.bin - RAM image for the emulator

Casio fx-8000G Chess

Entering unprotected mode

Entering hex loader

Entering the program itself

Testing the game and cleaning up unnecessary programs

Source-object listing

Source listing of relocators

Files to download