IBM 3270
The 3270 series was designed to connect with mainframe computers, often at a remote location, using the technology then available in the early 1970s.
By ensuring the CPU is not interrupted at every keystroke, a 1970s-era IBM 3033 mainframe fitted with only 16 MB of main memory was able to support up to 17,500 3270 terminals under CICS.
In a data stream, both text and control (or formatting functions) are interspersed allowing an entire screen to be painted as a single output operation.
Some users familiar with character interrupt-driven terminal interfaces find this technique unusual.
Application program functions such as termination, page-up, page-down, or help can be invoked by a single key press, thereby reducing the load on very busy processors.
[15] IBM and third-party software that included an interactive component took for granted the presence of 3270 terminals and provided a set of ISPF panels and supporting programs.
The modified data tag is well suited to converting formatted, structured punched card input onto the 3270 display device.
IBM's OfficeVision office productivity software enjoyed great success with 3270 interaction because of its design understanding.
[citation needed] A version of the WordPerfect word processor ported to System/370 was designed for the 3270 architecture.
Many manufacturers, such as GTE, Hewlett-Packard, Honeywell/Incoterm Div, Memorex, ITT Courier, McData, Harris, Alfaskop and Teletype/AT&T created 3270 compatible[f] terminals, or adapted ASCII terminals such as the HP 2640 series to have a similar block-mode capability that would transmit a screen at a time, with some form validation capability.
In the early 1990s a popular solution to link PCs with the mainframes was the Irma board, an expansion card that plugged into a PC and connected to the controller through a coaxial cable.
Optional features for the 3275 and 3277 are the selector-pen,[g] ASCII rather than EBCDIC character set, an audible alarm, and a keylock for the keyboard.
Generally, 3277 models allow only upper-case input, except for the mixed EBCDIC/APL or text keyboards, which have lower case.
Lower-case capability and dead keys were available as an RPQ (Request Price Quotation); these were added to the later 3278 & 3279 models.
The 3290 is a Distributed Function Terminal (DFT) and requires that the controller do a downstream load (DSL) of microcode from floppy or hard disk.
Image data compression is a technique to save transmission time and reduce storage requirements.
The IBM 3194 is a Display Station that features a 1.44 MB 3.5" floppy drive and IND$FILE transfer.
Both implementations are supported by IBM GDDM — Graphical Data Display Manager first released in 1979, and by SAS with their SAS/GRAPH software.
The application i.e. GDDM sends the vector definitions to the 3179-G, and the work of activating the pixels that represent the picture (the vector-to-raster conversion) is done in the terminal itself.
The IBM 3482 terminal, announced in 1992, offered a printer port, which could be used for host addressable printing as well as local screen copy.
The 3274-1A was an SNA physical Unit type 2.0 (PU2.0), required only a single address on the channel for all 32 devices and was not compatible with the 3272.
During its life span, the 3274 supported several features including: IBM introduced the 3174[46] Subsystem Control Unit in 1986, replacing the 3274 product line.
It supported all the hardware modules present at the time, almost all the microcode features found in 3274 and introduced a number of new features including: Intelligent Printer Data Stream (IPDS), Multiple Logical Terminals, Country Extended Code Page (CECP), Response Time Monitor, and Token Ring configured as host interface.
In 1994, IBM incorporated the functions of RPQ 8Q0935 into Configuration Support-C release 3, including the TN3270 client.
[48][49][50][51] It's a combination of an Arduino shield with a BNC connector and a Python program that runs on a POSIX system.
3278 terminals continued to be manufactured in Hortolândia, near Campinas, Brazil as far as late 1980s, having its internals redesigned by a local engineering team using modern CMOS technology, while retaining its external look and feel.
NL, EM, DUP, and FM control characters display and print as 5, 9, *, and ; characters, respectively, except by the printer when WCC or CCC bits 2 and 3 = '00'b, in which case NL and EM serve their control function and do not print.
Other bit settings will sound the audible alarm if installed, unlock the keyboard to allow operator entry, or reset all the Modified Data Tags in the device buffer.
[14]: pp.75–90 Programmers hand-coding panels usually keep the table of addresses from the 3270 Component Description or the 3270 Reference Card handy.
Most 3270 terminals newer than the 3275, 3277, 3284 and 3286 support an extended data stream (EDS) that allows many new capabilities, including:
