(1) is a grammatical error. A semicolon cannot be used between abc's in a statement. It usually indicates the end of the statement.

② Grammatical errors. If you enter 5, you must enter X. When the program is running, you can manually enter 5 after the cursor.

③s=8 is the logical judgment in the algorithm. If you want to output s=8, it can only be used as a string, that is, double quotation marks should be added.