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

VOID M

MARK INIT1
SEEK -15
MARK INIT2
COPY 0 X

MARK LOOP
TEST F = -9999
TJMP INIT2
ADDI X 1 X
TEST X = 16
FJMP LOOP

SEEK -16

COPY 16 T
MARK LOOP2
COPY F M
SUBI T 1 T
TJMP LOOP2

TEST M = -1
TJMP INIT1
SEEK -16
COPY 16 T
MARK LOOP3
COPY F M
SUBI T 1 T
TJMP LOOP3

XB (global)

MAKE

MARK START
WIPE
MAKE
COPY -1 M
COPY 16 T

MARK LOOP
COPY M F
SUBI T 1 T
TJMP LOOP

SEEK -9999

MARK LOOP2
MULI F 2 X
TEST X > 9
TJMP SUBT
MARK BACK
SEEK -1
COPY X F
SEEK 1
TEST EOF
FJMP LOOP2

COPY 0 X
SEEK -9999

MARK LOOP3
ADDI X F X
TEST EOF
FJMP LOOP3

SWIZ X 1 X
TEST X = 0
FJMP START
COPY 1 M
COPY 16 T
WIPE
MAKE
MARK LOOP4
COPY M F
SUBI T 1 T
TJMP LOOP4
HALT

MARK SUBT
SUBI X 9 X
JUMP BACK

Results

Cycles	Size	Activity
12837	71	3