You can use VA Smalltalk to build a workstation-based, graphical user interface that can access host applications designed for 3270 terminals. Rather than requiring users to enter data in a 3270 terminal emulator session, a VA Smalltalk application can interact directly with the host application. From the host application's perspective, the VA Smalltalk application appears as a user at a 3270 terminal.

To communicate with host applications, VA Smalltalk uses the Emulator High-Level Language Application Programming Interface (EHLLAPI), a feature provided by 3270 terminal emulators such as IBM's eNetwork Personal Communications product.

To communicate with 3270-based applications, VA Smalltalk uses the 3270 Screen part, located in the 3270 Hllapi category on the parts palette. Each 3270 Screen part represents a specific host menu, panel, or other screen. To interact with multiple panels of a host application, you simply use multiple 3270 Screen parts, each set up for a different host panel.