>What is the limit of CASE in a DO CASE ?

I don't think there is one.

But for practical reasons, please consider the following example:

do case
case x = 1
  ...
case x = 2
  ...
case x = 3
  ...
...
case x = 500
  ...
endcase

If "x" happens to be equal to 500, Visual FoxPro must analize all 500 cases, before carrying out the desired action. If this happens often, i.e., in a tight loop, performance will be bad. It might be much more efficient to split it, for example, as follows:

do case
case x <= 100
  do case
  case x <= 10
    case x = 1
      ...
    case x = 2
      ...
  case x <= 20
    case x = 11
      ...
    case x = 12
      ...
case x <= 200
...

Or something similar. Much less CASEs to be analyzed, for any given number.