README.md

30: Holman Dynamics (Sales System)

Instructions

Create a file in your host containing the contiguous 16-value sequence from the garbage file (file 199) that is a valid credit card number. There will be exactly one such sequence.

For more information see "How to Validate Credit Card Numbers" in the second issue of the zine.

Solution

XA (global)

LINK 800
LINK 802
LINK 799
GRAB 199

; FIX EDGE CASE VERY END
SEEK 9999
COPY -9999 F
SEEK -9999

; FIND 16 SEQ
MARK RESET
COPY 0 X
MARK LOOP
ADDI X 1 X
TEST F < 0
TJMP RESET

TEST X > 15
FJMP LOOP

; FOUND
SEEK -16
COPY 0 X
COPY 0 T

@REP 8
COPY F M
ADDI M T T
SEEK 1
@END

SEEK -15
@REP 8
ADDI T F T
SEEK 1
@END

SWIZ T 0001 T
FJMP VALID

; RESET COUNTER TO -1
SEEK -1
COPY 15 X
JUMP LOOP


MARK VALID
MODE
REPL DUPE
SEEK -17

@REP 16
COPY F M
@END

SEEK 9999
SEEK -1
VOID F

HALT

MARK DUPE
MAKE
@REP 16
COPY M F
@END

LINK -1
LINK -1
LINK -1
KILL

XB (global)

; TRANSFORM ODD #
JUMP LOOP

MARK GREATER
SUBI X 9 M

MARK LOOP
MULI M 2 X
TEST X > 9
TJMP GREATER

COPY X M
JUMP LOOP

Results

Cycles	Size	Activity
4459	119	7