Compared to modern devices like the iPhone and iPad, early computers seem very archaic. They were large, often requiring huge, custom-built rooms to house them, they were delicate, needed large air conditioners and constant cooling to keep them running, and they were slow. Early systems could handle only one job at a time, and programs had to be entered directly into the system via punch cards, magnetic tape, or paper.
As computing systems evolved and became more capable, efforts were made to make more efficient use of available computing power. Operating systems and technologies were developed that allowed multiple users to access the host system from a convenient location both simultaneously and interactively. One such technology was the computer terminal.
Computer terminals were devices typically consisting of a cathode ray display tube and keyboard used to interface with a host system. Early terminals were called “green screens” thanks to the very common monochrome phosphor screens that most terminal displays sported. Another common nickname was ‘Dumb Terminal’ in reference to the fact that all processing was done by the host system and real terminals could do almost nothing themselves. In fact, the host computer needed to constantly check the connection to the terminal to determine if there had been any user input. This placed a heavy load on the main processing unit with a lot of valuable computing time devoted to terminal rounds; 40% of available computer time was not unheard of. The larger the installation, the more users and terminals, the more time was wasted.
To overcome this problem, ‘smart’ terminals were introduced along with dedicated IO (input/output) processing units. Smart terminals were named for their ability to handle relatively simple processing locally, such as validating user input fields and the ability to allow the user to move around a form by adding data. When the user completed the form, the terminal sent the results of the user’s input to the host as a data block. These smart terminals are also called ‘block mode’ terminals.
System manufacturers soon realized that they could be more profitable by making their products unique and attracting customers to their own product range. The net result was that each manufacturer had its own range of terminals that were largely incompatible with each other’s host system. The purchase of a particular host computer system required the purchase of compatible terminals from the same manufacturer. As a consequence of this, during the 1960s onwards, there existed a relatively large number of different computer companies, each with their own unique and incompatible terminals.
However, the end of the 1970s saw the reversal of this trend and the development of more standardized and general-purpose machines by some of the newer players in the computer industry, most notably Digital Equipment Corporation (DEC). These machines used a standard serial connection along with standardized character sets and ‘escape sequences’ (commands used to determine text formatting, layout, and other display options in a terminal). This made it much easier for other manufacturers to connect terminals and equipment to a host system.
Thanks largely to this openness and the size of the market that existed for terminals, a number of companies emerged whose sole business was to produce terminals for connection to host systems made by others. These companies created terminals that could connect to any number of the systems available on the market, and often had functionality that made them a cross between dumb and smart terminals without the costs of the latter. Terminals from manufacturers such as Televideo featured unique and highly desirable functionality that software developers took advantage of to enhance their own applications. In doing so, the software became dependent on the hardware again, though in this case the terminal rather than the host system. (The software could run on different host systems as long as the application could be ‘ported’).
Finally, in the modern era, the computer terminal has been almost completely replaced by the ubiquitous, multifunctional PC. In the early days of the PC, it was common to find a PC literally sitting next to a computer terminal on a user’s desk. However, it wasn’t long before this misuse of valuable desktop space and duplication of investment in the PC and Terminal became an issue. The solution to this problem came in the form of a program that ran on the PC and mimicked the function of the terminal, the Terminal Emulator.
Terminal Emulation software put an end to the expense of buying and maintaining terminals, with their limited and specialized functionality. Through a terminal emulator, users can access host systems directly from their PC. Terminal Emulator software replicates the functionality and behavior of multiple types of terminals and is available in versions that run a variety of devices found in the modern workplace, such as a handheld computer, mobile phone, or even a smartphone. through a web browser. In many cases, Terminal Emulation software integrates with word processors, spreadsheets, email, etc., dramatically lowering the cost of host access while improving capability and presenting the end user with a familiar and user-friendly interface. modern to older technology.