ISPRN() Detects printer ready (or not) on LPT1, 2 or 3

 Returns
 <lReady> => printer ready

 Syntax
 ISPRN(nPort)

 Description
 <nPort> is either 0, 1 or 2, corresponding to LPT1,
 LPT2 or LPT3

 Examples
  if ISPRN(0)
    MSG("LPT1 is ready")
  elseif ISPRN(1)
    MSG("LPT2 is ready")
  elseif ISPRN(2)
    MSG("LPT3 is ready")
  endif

 Warnings:
 Will not ALWAYS work reliably on a network
 (redirected) printer

 Source: ISPRN.ASM