A fleeting History of Computer Terminals
Compared to modern devices like the iPhone and iPad the very first computers seem very ancient indeed. They were large, often requiring huge custom built rooms to house them, they were delicate, needing large air conditioners and continued cooling to keep operational, and they were slow. The earliest systems could manager only a single job at a time and programs needed to be fed directly into the system by punch cards, magnetic or paper tape.
As computer systems evolved and became more capable efforts were made to make more effective use of the obtainable computing strength. Operating systems and technologies were developed that allowed multiple users to access the great number system from a comfortable location both simultaneously and interactively. One of those technologies was the computer terminal.
Computer terminals were devices typically consisting of a cathode ray characterize tube and a keyboard that was used to interact with a great number system. Early terminals were referred to as ‘Green Screens’ thanks to the very shared monochrome phosphor characterize screens sported by the majority of terminal screens. Another shared nickname was ‘Dumb Terminal’ in reference to the fact that all processing was handled by the great number system and the actual terminals could do almost nothing for themselves. In fact, the great number computer needed to regularly check the connection to the terminal to determine whether there had been any input from the user. This placed a large load on the main processing unit with much valuable computing time spent doing the rounds of the terminals; 40% of obtainable computer time was not unheard of. The larger the installation, the more users and terminals, the more time was wasted.
To conquer this problem ‘Smart’ terminals were introduced along with dedicated IO (input/output) processing units. Smart terminal were so named for their ability to manager some comparatively simple processing locally such as validation of user input fields and the ability to allow the user to move around a form adding data. When the user had completed the form the terminal would send back the results of the user input to the great number as a block of data. These smart terminals are also called ‘block mode’ terminals.
System manufacturers soon realized that they could be more profitable by making their products rare and locking customers into their own product range. The net consequence was that each manufacturer had its own range of terminals which were largely incompatible with anyone else’s great number system. The buy of a particular mainframe computer system required the buy of compatible terminals from the same manufacturer. As a consequence of this during the 1960s and onwards there existed a comparatively large number of different computer companies each with their own rare and incompatible terminals.
However the end of the 1970s saw the reversal of this trend and the development of more uniform and general purpose machines from some of the computer industry’s newer players, most notably Digital Equipment Corporation (DEC). These machines used a standard serial connection along with uniform sets of characters and ‘escape sequences’, (commands were used to determine the text formatting, layout, and other characterize options on a terminal). This made it much simpler for other manufacturers to connect terminals and equipment to a great number system.
Thanks largely to this openness and the size of the market that existed for terminals a number of companies emerged whose only business was to produce terminals for connection to great number systems manufactured by others. These companies produced terminals that could connect to any number of the obtainable systems 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 sported highly desirable and rare functionality that software developers took advantage of to enhance their own applications. In doing so software became dependent on hardware again, although in this case the terminal instead of the the great number system. (Software could be run on different great number systems so long as the application was able to be ‘ported’).
Finally, in the modern era the computer terminal has now almost thoroughly been replaced by the ubiquitous and multi functional PC. In the early days of the PC it was shared to find a PC literally sitting alongside a computer terminal on the desk of the user. However it did not take long for this very poor use of valuable desk space and the duplication of investment in the PC and the Terminal to become 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 purchasing and maintaining terminals, with their thin and specialized functionality. by a Terminal Emulator users are able to access great number systems directly from their PC. Terminal Emulator software replicates the functionality and behavior of multiple terminal types and is obtainable in versions which run a variety of devices found in the modern workplace, for example a hand held computer, a mobile phone or already by a web browser. In many situations Terminal Emulation software integrates with information processors, spreadsheets, email and so on, dramatically reducing the cost of great number access while enhancing capability and presenting the end user with a familiar and modern interface to older technology.