LabWindows/CVI (CVI is short for C for Virtual Instrumentation) is an ANSI C programming environment for test and measurement developed by National Instruments. The program was originally released as LabWindows for DOS in 1987, but was soon revisioned (and renamed) for the Microsoft Windows platform. The current version of LabWindows/CVI (commonly referred to as CVI) is 2015.
LabWindows/CVI uses the same libraries and data acquisition modules as the better known National Instrument product LabVIEW, and is thus highly compatible with it. LabVIEW is targeted more at domain experts and scientists and CVI more towards software engineers that are more comfortable with text-based linear languages such as C.