The vast majority of programmable bench instruments, whether GP-IB or LXI, use a command language known as SCPI, Standard Commands for Programmable Instrumentation.  

SCPI is widely deployed in the industry today by dozens of vendors.  It offers interoperability and ease of use.  Instruments may be programmed from any operating system, since the interpretation of the ASCII commands is performed by the instruments, not instrument drivers.

That also is its weakness.  Perhaps it is unfair to say that SCPI also means Slow but Compatible Programmable Instruments, but the speed improvements demonstrated by memory-mapped modular systems have been repeated time and time again by multiple vendors. 

In this article I will review a little history, and articulate the strengths and weaknesses of the SCPI standard.  Read the whole thing here.