Before you start using NI-VISA, it is helpful to learn some of the terminology commonly used throughout the development process.
A VISA resource is any instrument in your system. If you have multiple instruments connected to one host, each instrument is considered a VISA resource. The resource is a complete description of the set of capabilities for the instrument.
The VISA resource type will depend on your instrument. There are several types: INSTR, SOCKET, RAW, etc.
VISA Resource Name (Instrument Descriptor)
The VISA Resource Name is the exact name of the VISA resource. It specifies the instrument interface type, the instrument address, and the VISA Session type. The VISA resource name control is used to communicate with the instrument in your development environment. Use this information to see if your instrument is recognized and addressed properly in your program.
A VISA session is a path of communication to a VISA Resource. A session is opened using the operation viOpen(). You must open a VISA Session any time you want to perform VISA communication to an instrument.
A VISA alias is the nickname for a VISA Resource. The alias provides a friendly name to easily identify an instrument.