question about Bill William's fractal indicator codes for pro real time

Hi, I'm new to this site, and have a question about Bill William's fractal indicator codes for pro real time. I found this code for fractals and can't seem to get it to work, could you please help? What would [PC] be? Thank you.
code:
// CP=variables -default=2
if high[PC]>= highest [2*CP+1](high)then
LH=1
else
LH=0
endif
if low[PC]<=lowest [2*CP+1](low) then
LL=-1
else
LL=0
endif
if LH=1 then
HiL=high[CP]
endif
if LL=-1 then
LoL=low[CP]
endif
LoL coloured return (255,0,0)as "low" coloured HiL(0,255,0)as "high"
/////////////end