Classification is used to indicate which program component the tag can be used in. Depending on the label settings, the editor can select different categories. The categories that can be selected in the FB tab settings (FB screen) are as follows. Classified content variables are labels of internal variables that can be used in FB programs. VAR_CONSTANT is the label of a constant that can be used in FB programs. VAR_RETAIN* 1 is a latch tag that can be used in FB programs. VAR_INPUT is an input label, which is used for the input of FB program. You can't change the value in the FB program. VAR_OUTPUT is a label (output label) used in the output of FB program. VAR_IN_OUT is a label (input-output label) whose input and output can use the same name. This value can be changed in FB program. *1:not supported by FX CPU.