Thanks very much for the explanation. To confirm one more point, does the phrase “has not been typed previously” mean that there is no explicit type declaration nor implicit statement (that determines the type of a) above the data statement? If so, my code above is invalid in the proposed new standard (if no compiler extension is available), while valid in the current standard? If it is invalid in the new standard, I guess the sentence in the above document (Sec.8.6.7) should be modified as
A variable that appears in a DATA statement and has not been typed previously
shall cause an error.
or similar, because the default is now implicit none and no type information is available for a when the processor meets this DATA statement. Does this understanding seem correct…? (Or, does the semantic of DATA statement itself need reconsideration…?)