Terminal emulation refers to a type of software that allows end users to access a host computer or mainframe. The original terminals of the 1960s and '70s were crude pieces of hardware that performed a single function: accessing their host. Because of these limited capabilities, terminals did not survive in the multi-functional modern computing environment. Instead, terminal emulation software was introduced to mimic the original terminal hardware on a modern PC.
But first we must understand mainframes...
To understand the history of terminal emulation, it's useful first to understand the history of mainframe computers. Back in the 1960s and '70s, there was no such thing as a personal computer; instead, there were large mainframes the size of small refrigerators which sat in a specially-designed room and could be accessed by users who shared its processing power, memory, software and so forth. This "centralized" form of computing stood in stark contrast to the distributed, personal computer based solutions of modern computing, where information is shared across a decentralized network.
In order to access these mainframes, users had to connect to them via a terminal. These terminals were cathode ray monitors with a separate keyboard that allowed the user to enter text-based commands which would be relayed to the mainframe before immediately displaying the mainframe's return output. These were commonly referred to as "green screens", a phrase which originated from the common practice of using green phosphor based cathode ray tubes in early terminal screens.
What happened to terminals?
As mentioned, terminals were crude, single-function devices that weren't particularly user-friendly -- at least, not when compared with modern operating systems. As a result, terminals fast became obsolete. The problem, however, was that mainframes didn't. Mainframes are still as relevant as ever today, with the vast majority of the world's Fortune 500 companies still utilising them to ensure maximum up-time and performance for their millions of customers. And in order to access a mainframe, you need a terminal.
An early solution to this problem was submitted by companies such as WYSE, which produced 'multiple personality' terminals that could emulate other terminals, as well as their own, at a hardware level. In the end, however, the technology was still too crude when compared with the arrival of the PC with its user-friendly interfaces and multi-function capacities. A solution needed to be created which incorporated the PC.
The arrival of terminal emulation
Enter terminal emulation which, as discussed earlier, refers to software that mimics the role of terminal hardware on a PC, allowing users to access mainframes as they wish. These days a wide variety of terminal emulation software is available, including 3270 emulation, 5250 emulation, Wyse terminal emulation and so forth. These emulators run on a variety of platforms, including Microsoft Windows desktop operating systems, embedded systems (devices such as, for example, barcode scanners, industrial computers and POS computers) and, increasingly, smartphones.
Many commentators have predicted the demise of the mainframe, but the mainframe remains as important to modern business as ever. And as long as the mainframe remains so, terminal emulation software will be required in order to access it.