TN3270 Plus Windows HLLAPI (WinHLLAPI)

Important Notice!

Dear SDI Customers,

We regret to inform you that as of 9/26/2025, SDI USA has ceased all operations. Due to the lack of sufficient management structure and an aging workforce, we are no longer able to meet the high standard of support and service our customers deserve. As such, we have made the difficult decision to terminate our company's operation.

Licensed customers are authorized to continue using their licensed software products without further License or Maintenance and Technical Support fees. However, no Technical Support services will be available. The software products affected by this change include TN3270 Plus, SDI LPD, and any other software licensed by SDI USA in the past. There will be no future product updates, no new releases, and no new licenses. The products should continue to perform their intended function until changes to the operating environment make it incompatible with our products. Feel free to continue using the products for no cost until you decide to move to another supplier.

We intend to keep the sdisw.com website available, but unmonitored until 12/31/2026. We recommend that you download the installation files, user guides and sample files and keep them in a safe place for your future use before the web site closes down.

We have witnessed monumental changes in the computer software industry during the past fifty plus years and have enjoyed working with so many outstanding companies and wonderful people over those years. We wish you all a prosperous future.

SDI USA

Windows HLLAPI (WinHLLAPI)

Definitions

WinHLLAPI	Windows High Level Language Application Programming Interface. Windows HLLAPI (WinHLLAPI) is based on IBM's EHLLAPI specification. WinHLLAPI includes the EHLLAPI facilities and also includes Windows-specific extensions that allow the programmer to take advantage of the message-driven nature of Windows. WinHLLAPI is part of Microsoft's Windows Open Systems Architecture (WOSA). The current WinHLLAPI specification is version 1.1. This specification was developed in 1993 by Microsoft Corporation, Digital Communications Associates, Inc., Attachmate Corporation, Wall Data Incorporated, Synapse Communications, and NetSoft.
EHLLAPI	Extended High Level Language Application Programming Interface. An extension to HLLAPI.
HLLAPI	High Level Language Application Programming Interface. Was the original terminal emulator interface developed by IBM in the 1980's. This interface was designed to allow user-written applications to send data to and receive data from a terminal emulator. The term "screen-scraping" was often used to describe reading data from the terminal screen using HLLAPI.

Overview

The purpose of WinHLLAPI is to allow applications to communicate with a host computer much like a user at a 3270, 5250 or VT100 terminal. TN3270 Plus provides the connection and communication with the host computer. Your application can send commands to the host computer and receive data back from the host computer all via WinHLLAPI. Here are some applications for WinHLLAPI.

Automate connection and logon procedures.
Allow unattended file transfer or data processing during off hours.
Combine data from multiple hosts.
Develop customized user interfaces for zSeries (mainframe) applications.

TN3270 Plus WinHLLAPI supports most of the functions in the Windows HLLAPI Version 1.1 specification. See WinHLLAPI Unsupported Functions in the TN3270 Plus Help file for a list of functions that TN3270 Plus does not support.

How WinHLLAPI Works

Your application needs to load the Whllapi.dll distributed with TN3270 Plus. Once this is done, your application may call the Whllapi.dll functions to send data to, or receive data from, the host computer. Whllapi.dll is an extension of TN3270 Plus and it uses TN3270 Plus to send data to, or receive data from, the host computer.

Sample Programs