+
Solution to Assemble Me
+
+
+Author: Robert L. Rucinski
+
+
+
The flavortext (as well as the included link to the emulator) hints that this is a program for the Commodore 64 (also confirmed by the BASIC program with the command SYS 49152, which is a common command for the C64 to execute a user-defined machine language program).
+
+
The DATA statements are told to be mixed up, thus requiring them to be "assembled" (jigsaw puzzle-like) correctly to form a working program.
+
+
To solve this part of the puzzle, you can reference any number of works on the internet such as: http://www.commodore.ca/manuals/c64_programmers_reference/c64-programmers_reference_guide-05-basic_to_machine_language.pdf
+
+
First, determine what instructions each line of DATA represents.
+The first line of DATA represents the instructions: ADC $C060,Y; STA $C100,Y; INY; CPY #$23; BNE (-16)
+The second line represents the instructions: BCC (+2); LDA #$2A; JSR $FFD2; INY
+Etc.
+
+
By understanding what the different pieces of code do, it is possible to reconstruct the program (shown below). Input the program, with the DATA lines in the correct order into a C64 emulator (see ASSEMBLE.D64 for a working copy of the final program: mount the disc image in the VICE emulator, then LOAD "ASSEMBLE",8 and RUN).
+
+
The correct order of the DATA statements to make a working program is as follows:
+
+
+100 DATA 162,0,185,64,192,32,210,255,200,192,32
+110 DATA 208,245,160,0,24,152,121,129,235
+120 DATA 121,96,192,153,0,193,200,192,35,208,240
+130 DATA 162,0,160,0,169,32,24,30,0,193
+140 DATA 144,2,169,42,32,210,255,200
+150 DATA 192,8,208,238,232,224,35
+160 DATA 208,231,169,13,32,210,255,96
+170 DATA 147,13,84,72,69,32,65,78,83,87,69,82,32,84,79,32
+180 DATA 84,72,69,32,80,85,90,90,76,69,32,73,83,58,13,13
+190 DATA 234,240,225,241,117,133,131,232,71,32,197,209,154
+200 DATA 34,45,0,203,155,38,179,185,181,150,19,179,158,175
+210 DATA 173,36,157,157,137,167,18,144
+220 DATA 256
+
+
+
+When the program is run, the program gives:
+
+THE ANSWER TO THE PUZZLE IS:
+
+******* ******* ***** *******
+ * * * * *
+ * * * * *
+ * * ******* ***** ******
+ * * * * *
+ * * * * *
+ * ******* ***** ******
+
+
+
+
C64 Program for ASSEMBLE ME
+
+
C64 disc image with program (mount in the VICE emulator)
+
+
+;main program
+ *= $C000 ;assemble at $C000
+
+;clear screen and print "THE ANSWER TO THE PUZZLE IS: "
+
+ LDY #$00
+prloop1 LDA $data1,Y
+ JSR $FFD2
+ INY
+ CPY #$20 ;print all 32 characters
+ BNE $prloop1
+
+;change the 35 bytes of data in lines 190-210 into the graphical output
+
+;Those 35 bytes are essentially a coded way to produce the graphical output.
+;This section essentially decodes it into the correct bytes needed to print
+;the graphic (see below for how that happens). The encoding uses the C64
+;keyboard table at $EB81. Essentially, add the byte position, the C64
+;keyboard table value, and the byte to decode it. This has all been done
+;so as to encode the solution to the puzzle in the DATA and make it
+;impossible to determine the solution from the DATA alone.
+
+ LDY #$00 ;initialize loop counter
+chgnxtbyte CLC
+ TYA ;.A = counter (ie. 0th byte, 1st byte, etc)
+ ADC $EB81,Y ;.A = .A + keyboard table value
+ ADC $offsets1,Y ;.A = .A + data byte
+ STA $C100,Y ;store decoded byte in $C100+.Y
+ INY
+ CPY #$23 ;there are 35 bytes of data
+ BNE $chgnxtbyte
+
+;print the graphical output
+
+;$C100-$C122 now has decoded data such that each bit tells this routine
+;which character to print. If the bit is 0, print a space; if the bit is 1,
+;print an asterisk.
+
+ LDX #$00 ;initialize loop counter X
+nextchar LDY #$00 ;initialize loop counter Y
+
+nextbit LDA #$20 ;prepare to print a space
+ CLC
+ ASL $inputs1,X ;check bit
+ BCC $prchar ;if 0, branch
+ LDA #$A2 ;if 1, prepare to print an asterisk
+prchar JSR $FFD2 ;print a space or the character
+ INY
+ CPY #$08 ;have we done all 8 bits?
+ BNE $nextbit ;if not, do the next bit
+
+ INX CPX #$23 ;correct graphic takes 35 characters
+ ;have we done all 35 characters?
+ BNE $nextchar ;if not, do the next character
+
+ LDA #$0D ;print a carriage return
+ JSR $FFD2
+ RTS ;end
+
+data1 .byte $93,$0D,$54,$48,$45,$20
+ .byte $41,$4E,$53,$57,$45,$52,$20
+ .byte $54,$4F,$20,$54,$48,$45,$20
+ .byte $50,$55,$5A,$5A,$4C,$45,$20
+ .byte $49,$53,$3A,$0D,$0D
+
+offsets1 .byte $EA,$F0,$E1,$F1,$75
+ .byte $85,$83,$E8,$47,$20
+ .byte $C5,$D1,$9A,$22,$2D
+ .byte $00,$CB,$9B,$26,$B3
+ .byte $B9,$B5,$96,$13,$B3
+ .byte $9E,$AF,$AD,$24,$9D
+ .byte $9D,$89,$A7,$12,$90
+
+
+