A computer firm countersued its former president.

Commodore International Ltd. filed the $24-million countersuit against its former president and chief executive, Thomas J. Rattigan, who resigned in April and sued it for $9 million, alleging breach of contract. Rattigan contended that Commodore undercut his authority and forced him out of office. But Commodore contends that Rattigan behaved antagonistically and was not entitled to the benefits from the four years that were remaining under his contract. Commodore’s countersuit alleges that Rattigan disobeyed the chairman and the board and behaved with “gross disregard” of his duties on such issues as financial controls, advertising, production, management changes and bonuses.