They were originally introduced in 1971 and they were used to give users access to programs running on on IBM mainframes.

What is an IBM 3270 (TN3270) Terminal? The IBM 3270 is a series of block oriented computer terminals (sometimes called display devices) made by IBM. In the past true IBM 3270 terminals were often used for this purpose, but with the advent of personal computing the use of like (on a computer running Windows or macOS) became the norm for TN3270 mainframes access, because it is considerably more cost effective than using genuine IBM terminals or even IBM 3270 emulation software. They can be used by thousands of users at the same time, but they need to be accessed through so-called terminals. Mainframes are large servers which are mainly used by businesses for large scale data processing. Overview: TN3270 is a terminal emulation standard developed by IBM to access Mainframes. Is a professional and feature-rich TN3270 which lets you access IBM zSeries and iSeries mainframes via normal or secure (SSL) telnet connections from a Windows PC or Mac. Ericom Terminal Emulator software for Mac OS X supports TN3270, TN5250 among 35 types of emulators.

Major features of the emulation include color, extended. Tn3270 is a terminal emulation program for connecting to computers which use IBM 3270 terminals.

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