SCPI or "Standard Commands for Programmable Instruments"

is mainly used by "Keysight Technologies" instruments. The idea behind this standard is to create common commands for common tasks. SCPI promotes consistency, from the remote programming standpoint, between instruments of the same class and between instruments with the same functional capability. For a given measurement function such as frequency or voltage, SCPI defines the specific command set that is available for that function. Thus, two oscilloscopes made by different manufacturers could be used to make frequency measurements in the same way. It is also possible for a SCPI counter to make a frequency measurement using the same commands as an oscilloscope. SCPI commands are easy to learn, self-explanatory and account for both novice and expert programmer’s usage. Once familiar with the organization and structure of SCPI, considerable efficiency gains can be achieved during control program development, independent of the control program language selected.

SICL or "Standard Instrument Control Library"

is a standard library used to communicate with instruments. It's incorporated into Keysight's "IO Suite" and in National Instruments "Max". The library can be used by graphical and textual languages.
SICL is a modular instrument communications library that works with a variety of computer architectures, I/O interfaces, and operating systems. Applications written in C/C++/C# or Visual BASIC using this library can be ported at the source code level from one system to another with no (or very few) changes.
SICL uses standard, commonly used functions to communicate over a wide variety of interfaces. For example, a program written to communicate with a particular instrument on a given interface can also communicate with an equivalent instrument on a different type of interface.

IVI-COM actually consists of two standards.

• The IVI part represents the "Interchangeable Virtual Instruments".
• The COM part represents the "Component Object Model" defined by Microsoft.

Systems designed using IVI-COM drivers enjoy the benefits of standardized code that can be interchanged into other systems. This code also supports interchange of measurement devices -- helping to prevent hardware obsolescence. Interchangeability is supported on three levels :

1. The IVI architecture specifications allow architectural interchangeability -- that is a standard driver architecture that can be reused.
2. The class specifications provide syntactic interchangeability which supports instrument exchange with minimal code changes.
3. The highest level of interchangeability is achieved by using the IVI signal specifications.