Why does dynamic C ignore my keystrokes?

After I compile and run something, Dynamic C completely ignores my typing. It’s acting as if the text buffer has gotten write protected. I can move around, I can search, but anything I type has no effect. Hitting backspace has no effect. Cut-n-paste have no effect. Version 10.21 of Dynamic C.

You have to hit F4. I gather this is a protection to make sure that you really intend to modify the source code that has just been used to program the controller.

Wow. That’s not a choice I would have made. We had “undo” in editors back in 1982. In 28 years, nobody’s invented the concept of tagging “this is the source version you compiled last”? Oh well, now I don’t have to restart DC after every compile now, thanks!