The Series 30, often shortened as S30, software platform is an application user interface created by Nokia for its entry level mobile devices. S30 phones are capable of running Java apps.
Despite being similarly named, Series 30+ is an entirely unrelated platform, licensed from MediaTek and used on later Nokia-branded feature phones made by Microsoft; unlike S30, it does not support Java apps.
Microsoft no longer uses S30 for its Nokia-branded mobile devices. Microsoft uses S30+ solely for these devices.