STARTVAL, STEPVAL, DURVAL, BIASVAL

Current values for START, STEP, DUR, and BIAS respectively.  Use these
values in expressions when you do not know their current values; for
example, whenever a procedure such as FFT, BINCNT, or READ
automatically resets these values to something calculated from the data
just processed.  (See the CAR.ALG algorithm for an example of how these
special constants can be usefull.) 
