<snip>

>Hi Ed, Of course, for C or Assembler, these type of error always occur.
>But as these part of code cannot be handled by programmer. The 4GL progr try all
>possible case to trace what these error may occur?! much seriously!
>
>Besides, I wonder no need other function call! That is, it will cause error
>even:
>

>= NVL(.NULL., _screen)
>

I ran this code, as well as:

  FOR i = 1 to 100
      =NVL(.NULL.,_SCREEN)
  ENDFOR

with no problems under VFP 5.0a, with no porblem to report.

>
>Maybe it is a weapon for fired progr to make a deadTime of program.

>If Date() >= {2000/1/1}
>  = NVL(.NULL., _screen)
>Endif
>

>and hide it in any superclass Init procedure!

Why?