For more explicit instructions:
Step 1: Run this in slot 0:
@A B$="Hi":PRINT B$It runs fine. Step 2: Run this in slot 0:
@A@B$="Hi":PRINT B$It generates a Syntax Error. Step 3: Run this in direct mode:
GOTO @AThe 'direct mode' cursor stops blinking for a couple of seconds. The system shows "An error has occurred, forcing the software to close. The system will now restart. (Unsaved data may be lost.)". Not every syntax-error-causing code in step 2 will cause this. New 3DS, SmileBasic 3.3.2.