format: dd ww ff 00, e.g. F40.1 is 01 28 05 00
01 - double (01 58 format double)
-02 - instance of a numeric variable (02 58 format double "varname" "Variable Label")
+02 - instance of a numeric variable (02 58 format double "varname" "vallab")
03 - just a string (03 "Short Name" 58 "identifier" "Long Name")
04 - instance of a string variable (04 58 format "vallab" "varname" 02 "value"
05 - variable (05 58 "varname" "Variable Label")