Checks (selects) the corresponding symbolic definition field in the current app. The integer n must be between 0 and 9 for most apps. For Statistics 1-Var and Statistics 2-Var apps, n must be between 1 and 5.
CHECK(3) would check F3 if the current app is Function. Then a checkmark would appear next to F3 in Symbolic view, F3 would be plotted in Plot view, and evaluated in Numeric view
CHECK — Discussion