A type is a pattern containing all the characteristics of the data description unit and its subordinate data items. A type is defined by specifying the TYPEDEF clause. The principal characteristics of a type which is identified by its type name are the relative positions and lengths of its elementary items which are defined in the type declaration, plus the BLANK WHEN ZERO clause, JUSTIFIED clause, PICTURE clause, SIGN clause, SYNCHRO-NIZED clause and USAGE clause which are specified for these elementary data items (for details on the clauses see the section "Data description entry").
The following data types exist:
weakly typed elementary items
weakly typed group items
strongly typed group items
Note: Elementary items cannot be strongly typed.
A type - whether weak or strong - defines a particular data structure which has a precisely specified name which is used precisely with this structure. This prevents the structure being affected, for example, by a different alignment or a change in the data representation through the USAGE phrase on higher-ranking group levels.