lingo：subscript out of range on attribute Q

为什么下面程序用lingo运行时出现subscript out of range on attribute 求解释? subscript out of range 什么意思? “subscript out of Run-time error'9':subscript out of out of range out of range是什么 out of range 啥意思 显示器提示 OUT OF RANGE string index out of range String index out of range:-1 scan line index out of range String index out of range:0