IBM 3270 Green Screen

The great thing about green screens is that they are so easy and so quick to use. Basically, a screen appears, you enter some information, press tab, enter some more information, and press enter. It’s quick, it’s simple to use, what’s not to like? And that’s how so many mainframers feel. They’ve been using green screens since they were really green to get their work done accurately and efficiently. ISPF, SDSF, and SMP/E are just so straightforward to use with a 3270 display.

So, how did all this start? The IBM 3270 terminal first saw the light of day in 1971 as a way to communicate with the mainframe. At that time, display screens were very expensive, and therefore used a zinc sulphide coating, because it was the cheapest way to get a screen that was bright enough display to be useful. And the result was green characters on a dark background. The words (there were no pictures) that appeared arrived in large blocks of data known as data streams, and the screen was mapped so that it would only accept text in certain fields. Often, a screen’s worth of information would be 24 lines by 80 characters.

The later 3279 came with a colour screen – but it was still referred to as a green screen. IBM stopped making 3270 terminals, but the protocol continued to be used, allowing people to access the mainframe in terminal emulation mode. Back in the early 1990s, every connection used SNA, but people gradually switched to Telnet, which was a popular protocol for the Internet or local area networks because it provided a bidirectional interactive text-oriented communication facility using a virtual terminal connection. Nowadays, you don’t hear very much about Telnet because of security issues –  people now use SSH. Telnet 3270 (tn3270) describes both the process of sending and receiving 3270 data streams using the Telnet protocol and the software that emulates a 3270 class terminal communicating using that process. What made it so successful was that tn3270 allowed a 3270 terminal emulator to communicate over TCP/IP instead of SNA.

But things never stay the same for long in IT, and even though experienced mainframers were getting work done speedily and efficiently on their green screens, the rest of the world was using browsers and enjoying lots of colours and pictures – something that 3270 emulators couldn’t quite match. A whole generation of IT people grew up wanting to use a GUI to talk to the mainframe – they wanted the same flexibility as a browser screen. New users were surprised (horrified) when they saw the antiquated looking green screens being used – even though mainframers could get more work done in less time using them than using the pretty browser windows.

And that’s where mainframe environments are today and. How do you make your mainframe applications palatable for younger, GUI-loving people, while at the same time allowing your experienced (but older) staff to continue to quickly get work done using their familiar ‘green screens’?

One possible solution (although the odds are quite long at this stage) is to do away with systems programmers because they can be replaced by Artificial Intelligence (AI). The fact that Watson will now run on mainframes makes it possible that it will become such a powerful AI that people won’t be needed to do anything to keep z/OS running optimally. And it will even troubleshoot itself and install PTFs, etc.

Or, we can use some kind of emulation software that will convert the 3270 protocol to HTML (and perhaps JavaScript – it’s worth noting that Oracle deprecated the Java plug-in in early 2016 because of security exposures). And that’s what some sites have done over the past 10-plus years. And you can use the result on a browser on a laptop, phone or tablet. The interface certainly looks like the kind of thing that younger IT people are very familiar with. You can find software that serves up 3270 screens as standard HTML Web pages. It can then use an HTTPS connection for security and emulate a 3270 screen. That allows a browser on any device to run the emulation software.

Another option for development work is to use Eclipse. The reason for that suggestion is that younger people are probably familiar with it because they may well have used it for Java development already, and it’s Open Source, and it’s supported by IBM.

So, in conclusion, let me confirm that, like so many mainframers, I love green screens. I just know that moving forward, all-singing and dancing software is the way to attract younger people into the world of Big Iron.

Trevor Eddolls

Trevor Eddolls

CEO at iTech-Ed
Regular Planet Mainframe Blog Contributor
Trevor Eddolls is CEO at iTech-Ed Ltd, and an IBM Champion for the eight years running. He currently chairs the Virtual IMS and Virtual CICS user groups, and is features in many blogs. He is also editorial director for the Arcati Mainframe Yearbook.
Trevor Eddolls

Latest posts by Trevor Eddolls (see all)

Share this article: Share on Facebook1Share on Google+0Tweet about this on Twitter0Share on LinkedIn36Email this to someone

Leave a reply

Your email address will not be published. Required fields are marked *