When you hear somebody use the term 'Big Iron', they're probably referring to the IBM mainframes that rose to prominence in the 1960s. These computers are large, expensive and powerful, often taking up entire rooms with their own cooling systems. In the '60s, large corporations in key industries such as banking, telecommunications and airlines began using the large scale computer system architectures commonly referred to as Big Iron, and these architectures continue to play an important role today. In this article we'll look at the history of Big Iron, as well as how the traditional "green screen" terminals used to access them became obsolete, being replaced with user-friendly terminal emulation software.

IBM System/360

In the 1960s, IBM reinvented business computing when it introduced System/360, a mainframe computer system that introduced scalability into the mainframe platform. Up until this point, business computing was still very much in its infancy. While the "Big Iron" of the day was still extremely powerful, it could not be upgraded without purchasing a new system entirely. IBM had the idea of introducing a compatible family of computer systems that would suit any business purpose; businesses could purchase a smaller system knowing that, if their business requirements grew, they could always upgrade to a larger system without having to reprogram the application software entirely.

It was System/360 that provided the platform for NASA to put a man on the moon, and it also introduced the concept of "real-time transaction processing" that today enables credit card authorizations, airline reservations and basically any online system that returns information immediately. We take these technologies for granted today, but without Big Iron these technological developments would never have been possible in the first place. IBM would then go on to introduce System/370 and System/390.

IBM System Z

Modern Big Iron comes in the form of IBM System Z, a rebranding of the existing System/390. It introduced IBM's newly-designed z/Architecture into the 64-bit mainframe world, enabling twice the performance of previous instalments -- something which big business was quick to take advantage of. The 'z' in z/Architecture stands for "zero downtime".

The Role of Terminal Emulation

Originally, Big Iron was accessed with the use of specially-designed terminals. These terminals were often referred to as "green screen" terminals because of their cathode ray tube (CRT) monitors with separate keyboards that had users entering nothing more than big, green characters onto the screen. These text-based commands simply sent instructions to the mainframe, and then displayed the mainframe's return output. They were much different from the types of interfaces we're used to seeing on our PCs today in the form of Windows and Mac operating systems.

We now access computers through user-friendly graphical interfaces, but the role of the mainframe is still important. Therefore, despite the fact that terminals have become obsolete, the role that the terminals play is still crucial as well. As a result, there has been a big need for terminal emulation software such as 3270 emulation in order to access Big Iron in the modern computing environment. The use of terminal emulation software enables businesses to harness the power of host systems, and allows Big Iron to remain relevant in the modern business environment