Different versions of the import utility is upwards compatible. This
means that one can take an export file created from an old export
version, and import it using a later version of the import utility. This is
quite an effective way of upgrading a database from one release of
Oracle to the next.
Oracle also ships some previous catexpX.sql scripts that can be
executed as user SYS enabling older imp/exp versions to work (for
backwards compatibility). For example, one can run
$ORACLE_HOME/rdbms/admin/catexp7.sql on an Oracle 8 database to
allow the Oracle 7.3 exp/imp utilities to run against an Oracle 8
database.