legacy system
Computing term for an old, often outdated system still in use, typically difficult to maintain or integrate.
その銀行はまだレガシーシステムを使っている。
That bank is still using a legacy system.
レガシーシステムの移行には多大なコストがかかる。
Migrating from a legacy system incurs enormous costs.
Variant with interpunct; less common in running text.
Borrowed from English 'legacy system', a compound of 'legacy' and 'system'.