Attributes may be used to extract information about many different
items in VHDL. Attributes can return various types of information.
For example, an attribute can be used to determine the depth of an
array, or its range, or its leftmost index, etc. Additionally, the
user may define new attributes to cover specific situations. This
capability allows user-defined constructs and data types to use
attributes. Another example of the use of attributes is in assigning
information to a VHDL construct, such as board location, revision
number, etc.
A few examples of predefined VHDL attributes are shown above. Note
that the apostrophe marking the use of an attribute is pronounced tick
(i.e. 'EVENT is pronounced "tick EVENT").
