Modernization Introduction

Welcome to the new set of posts about screen and spool modernization.

In this series we will guide you how to modernize old black and green terminals into modern Web UI. We will also describe screen maping definition formats and screen extraction formats, integration with various web frameworks from Bootstrap, Vue.JS, ExtJS and many more.

We already wrote about spool modernization in our tips&tricks tutorials. Here we will go one step further and show many tricks and cool stuff to create modern browser based reports.


In cloud and Internet era, we are witnessing that many big ERP systems are trying to find and applying various solutions for newer technologies including integrations with online services, modern web based applications, mail and office integration etc. Modernization and transition is expensive and long process which take years, often more than 10 years to complete the process.

We in Green Screens believe that the best approach is integration mix of manual development from scratch segment by segment and simplified web based manual screen templating. This enables partial transition step by step, screen by screen, program by program to new systems, but also extend life of legacy systems by enabling latest web technologies directly inside 5250 terminals.

Screen templating is our approach to screen scraping in a modern and simplified way allowing great flexibility and integrations options. Our advantage is usage of simple HTML based web templates for UI screen design without server-side programming. Process is simple, does not require extensive knowledge, young inexperienced developers can do it, time needed for education is 2-3hr.

Except screen templating Green Screens Terminal Service product support modern spool file (report) drivers allowing printing spools directly to browser as PDF, HTML, various image formats or even web standard JSON programable object.

We go one step further and enabled our modernization engine on mobile devices also. Develop templates in standard web forms and get great visual layer inside our mobile application.

While developing new system, existing can be easily adapted to new environment with just simple HTML templates. If both environment are web based on latest web standards, they can cooperate very well and from user point of view, they operate as a single entity. Integrated together it is hard to distinguish that this are two separate systems. They work as one.

Green Screens Web Terminal use extensive browser based API that can be used for integration with other products, to programmatically manipulate web terminal in all imaginable ways. There is no any other terminal based product with such level of flexibility.

There are three types of modernization techniques for legacy software: transpilation, screen scraping, and manual coding from scratch. Each of them have pros and cons and neither are universal solution. But, all of them are time consuming with different levels of cost. Keeping old is also not a solution because of lack of developers with know-how and integration problems with new technologies emerging every day.

Transpilation is fast approach with great results regarding visual appearance. However, migrated code usually is machine generated and extremely hard to maintain. Screen scraping is fastest approach but it creates only UI layer on top of old terminal screens, while programs remains intact and not migrated to newer technologies.

Manual programming is slowest, the most expensive but with the best results. While manual transition finish, software itself will become technologically obsolete.

Whichever approach is used, problem lays in long time needed to migrate or not sufficient integration features with existing web environment.

Existing transpilation and screen scraping solutions requires a great technical knowledge, are too complicated to install, to use, and generally tides a customer to a solution provider.

Existing screen scraping solutions in most cases create single non integratable environment – standalone product.

Transpilation and screen scraping solutions are desktop based and usually not online / cloud ready or very hard to implement. Often, they are limited to specific environments.

Neither of existing solutions support report – spool files modernizations.

All of existing solutions are based on techniques developed in a time when those products entered to the market – 10-15 years ago. That means, in most cases actual web technologies and standards are not used. Those products use obsolete technologies in many cases which have a reflection on security also.


Because of all mentioned above including our advanced web terminal, we introduced ETL engine responsible for web terminal screen to web standardized and technology independent JSON format conversion.

When we have screen data and screen fields in web standard format new horizon opens - new approach to modernization. Without need for server side code, for RPG or COBOL refactoring or transpilation which saves time and money.

We hope that you will find this series very interesting and helpful to your organization.

For more technical details, please refer to links below :
Web Terminal Modernization
Mobile Terminal Modernization