In version ATEasy 7, a VISA driver (visa.drv) is provided in the Drivers folder under ATEasy.

Virtual Instrument Software Architecture, commonly known as VISA, is a widely used I/O API in the Test & Measurement industry for communicating with instruments from a PC. VISA is an industry standard implemented by the VXIplug&play Systems Alliance (T&M companies), including Agilent Technologies and National Instruments.

The VISA standard includes specifications for communication with resources (usually, but not always, instruments) over T&M(Test and Measurement)-specific I/O interfaces such as GPIB and VXI. There are also some specifications for T&M-specific protocols over PC-standard I/O, VXI, USB, Ethernet (over TCP/IP), Serial(RS232), and PXI.

The VISA library has standardized the presentation of its operations over several software reuse mechanisms, including through a C API (Application Programming Interface) exposed from Windows DLL, visa32.dll and over the Microsoft COM technology.

VISA Specifications are found in IVI Foundation: http://www.ivifoundation.org.
 

If you want to use VISA APIs, you can insert visa.drv into your project system as :

The driver contains Visa 32 dll library with its procedures, types, and its constants.  To access APIs and its resources, in your code, type "Visa32." as shown here :