Data declarations

When a PL/I program is executed, it can manipulate many different data items of particular data types. Each data item, except an unnamed arithmetic or string constant, is referred to in the program by a name. Each data name is given attributes and a meaning by a declaration (explicit or implicit). This chapter discusses explicit and implicit declarations, scalar, array, structure, and union declarations, scope of names, data alignment, and default attributes.

Most attributes of data items are known at the time the program is compiled. For nonstatic items, attribute values (the bounds of the dimensions of arrays, the lengths of strings, area sizes, initial values) and some file attributes can be determined during execution of the program. See Block activation for more information.

Data items, types, and attributes are introduced in Data elements.