About pressing undo before taking the first step

[wsongah]

What should be the reaction of the program if the play pressed undo before the first step. Is it ok if the program run panel reports error?

[henryhchchc]

What should be the reaction of the program if the play pressed undo before the first step.

It should do nothing.

Is it ok if the program run panel reports error?

No, you should handle this case.