COMMENT Decide wether the content of Register 1 is even.
COMMENT The output is 0 if it is even and 1 otherwise

COMMENT initialization
ZERO 2

COMMENT main loop
LABEL loop
COMMENT invariant: R2 is even
EQ? 1 2 even
INC 2
COMMENT invariant: R2 is odd
EQ? 1 2 odd
INC 2
GOTO loop

COMMENT R1 holds an even number
LABEL even
ZERO 1
QUIT

COMMENT R1 holds an odd number
LABEL odd
ZERO 1
INC 1