VISA is an industry standard implemented by several T&M companies, such as, Anritsu, Bustec, Keysight Technologies, Kikusui, National Instruments, Rigol, Rohde & Schwarz, and Tektronix.
The VISA standard[1] includes specifications for communication with resources (usually, but not always, instruments) over T&M-specific I/O interfaces such as GPIB and VXI.
There are also some specifications for T&M-specific protocols over PC-standard I/O, such as HiSLIP[2] or VXI-11[3] (over TCP/IP) and USBTMC[4] (over USB).
Implementations from specific vendors [specify] are also available for less common programming languages [specify] and software reuse technologies.
The current standard, "VISA Specification 5.0", is maintained by the IVI Foundation.