xBase ?

Found entire article on wikipedia.

xBase is the generic term for all programming languages that derive from the original dBase (Ashton-Tate) programming language. There are indicators that there was a non-commercial predecessor.

The 'x' means the various flavors, such as dBase, (dBXL/Arago) QuickSilver, Clipper, FoxPro, xBase++, and xHarbour. As of this writing (April 2006), the following are commercially available: Visual FoxPro is available from Microsoft, Recital from Recital Corp., xBase++ from Alaska Software, Clipper from GrafxSoft, Flagship from multisoft GmbH, dBase from dBASE Inc., xHarbour Builder from xHarbour.com Inc.. Some free versions are also available, like: Clip, the Harbour Project and xHarbour.

A developer community support for xBase that is focused mainly on Clipper, FoxPro, [x]Harbour, and xBase++.