# Packed types

A declaration of a packed type has the form:

        TYPE T = BITS n FOR Base

where `Base` is a type and `n` is an integer-valued constant expression. The values of type `T` are the same as the values of type `Base`, but variables of type `T` that occur in records, objects, or arrays will occupy exactly `n` bits and be packed adjacent to the preceding field or element. For example, a variable of type

        ARRAY [0..255] OF BITS 1 FOR BOOLEAN

is an array of 256 booleans, each of which occupies one bit of storage.

The values allowed for `n` are implementation-dependent. An illegal value for `n` is a static error. The legality of a packed type can depend on its context; for example, an implementation could prohibit packed integers from spanning word boundaries.

    Last modified on Wed Apr  3 09:39:01 PST 1996 by heydon
         modified on Mon Apr 18 14:05:35 PDT 1994 by kalsow