Wang OIS
From Just Solve the File Format Problem
The Wang OIS was a dedicated word processing machine released in 1977 and popular in the corporate world through the early 1980s, until general-purpose PCs became more popular for such functions. Unlike the earlier Wang 1200 which used cassettes for storage, the Wang OIS used disks. However, its file formats and other tech specs were closely-guarded proprietary secrets, as Wang didn't want third-party developers interoperating with their devices and possibly undercutting their own market.
