Terminal Emulator

The Origin of Terminal Emulators

These terminals enabled the users to enter and view data, whereas the actual processing was done by the central computer. The terminals (thin clients) were devices which consisted of a screen, a keyboard, and the technology that allowed them to transmit keystrokes to and receive output from the server, but had no noteworthy computing power of their own.

With the success of Linux, the client/server concept and central computing has undergone something of a renaissance. As a direct result of this the necessity of using a terminal to access a computer located in a remote location (be it somewhere across the globe or server vault in the basement of the same building) is yet again receiving a lot of attention again.

Instead of using dedicated hardware terminals, today a terminal emulation software running on a modern computer provides the user with the means to access these servers.

However, to allow the server programs some flexibility, the terminals had some limited computing power that enabled them to perform tasks beyond merely printing all received text. Instead, they could receive specific codes which were embedded in the text, and use these to format the output of the text, rather than just printing text left-to-right and top-to-bottom like a teletype.

However, each manufacturer (e.g. IBM, Digital Equipment, Wyse Corp.) used different codes to perform the formatting of text, so the terminals to access a certain type of server needed to be bought from the manufacturer of the server. In other words, different manufacturers used different codes that the servers sent to the terminals in order to move the cursor, change the color, clear the screen and so on.

Among the best-known terminal manufacturers were DEC (who created the line very popular of VT-Terminals, including vt100, vt220 etc.) and IBM (using 3270 and 5250 terminals).

For example, on a VT220 or ANSI terminal, to send the text "this is an error!" to the user's screen with the word "error" in red, the host would actually send  This is an ^[31m error ^[0m!  to the terminal emulator. Rather than displaying all the text, the VT220 terminal will strip the cryptic code parts ^[1m  and ^[0m  as commands and will print the text between them in a different color.

As the use of computers has increased, data processing has once again become very demanding. Nowadays, it is not uncommon to need to access gigabytes of data in databases or to process extreme amounts of information. Because of this, the idea of server computing has been resurrected. Personal computers with memory and processors are still used for simple computing tasks such as word processing, but for more complex work users may need to access remote systems. Returning to the use of dumb terminals would be impractical - few people would have room for another keyboard and screen on their desk. Instead, software now plays the role of a dumb terminal. This software is called a terminal emulator, as it emulates a dumb terminal or thin client on a PC.

As noted above, many manufacturers used to develop their own terminals with their own type of ommunication between the server and the terminal. The good thing about modern terminal emulators is (compared to hardware terminals) that they can understand most of the codes that were used in the past. A single terminal emulation program like ZOC can actually play the role of both an IBM and a DEC terminal, depending on which server a user needs to access (e.g. an IBM mainframe or a Unix server).

As well as the basic terminal functions, ZOC offers a wealth of additional, useful features. This terminal emulator takes advantage of the computing power of a PC to allow you to automate tasks (such as logging on or retrieving data automatically), log sessions on screen or file (for documentation or later review), copy data between a text processor and the remote server, and much more.