IBM 3270
Encyclopedia
Block-oriented terminal
A block-oriented terminal is a type of computer terminal that communicates with its host in blocks of data, usually chunks of text, as opposed to a character-oriented terminal that communicates with its host one character at a time...
terminals
Computer terminal
A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system...
made by IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
since 1972 (known as "display devices") normally used to communicate with IBM mainframe
IBM mainframe
IBM mainframes are large computer systems produced by IBM from 1952 to the present. During the 1960s and 1970s, the term mainframe computer was almost synonymous with IBM products due to their marketshare...
s. As such, it was the successor to the IBM 2260
IBM 2260
The text-only 960-character monochrome IBM 2260 cathode ray tube video display terminal plus computer keyboard was a 1964 predecessor to the more-powerful color text-and-graphics IBM 3270. The 2260 screen image was normally configured with 12 lines of 80 characters each, which corresponded to IBM...
display terminal. Due to the text colour on the original models, these terminals are informally known as green screen
Monochrome monitor
A monochrome monitor is a type of CRT computer display which was very common in the early days of computing, from the 1960s through the 1980s, before color monitors became popular. They are still widely used in applications such as computerized cash register systems...
terminals. Unlike common serial ASCII terminals
Computer terminal
A computer terminal is an electronic or electromechanical hardware device that is used for entering data into, and displaying data from, a computer or a computing system...
, the 3270 minimizes the number of I/O
Input/output
In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...
interrupts required by accepting large blocks of data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
known as datastreams
Data stream
In telecommunications and computing, a data stream is a sequence of digitally encoded coherent signals used to transmit or receive information that is in the process of being transmitted....
, and uses a high speed proprietary communications interface, using coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
.
IBM stopped manufacturing terminals many years ago, but the IBM 3270 protocol is still commonly used via terminal emulation
Terminal emulator
A terminal emulator, terminal application, term, or tty for short, is a program that emulates a video terminal within some other display architecture....
to access some mainframe-based applications. Accordingly, such applications are sometimes referred to as green screen applications. Use of 3270 is slowly diminishing over time as more and more mainframe applications acquire Web
World Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...
interfaces, but some web applications use the technique of "screen scraping" to capture old screens and transfer the data to modern front-ends.
Principles
The 3270 series was designed to connect with mainframe computers, often at a remote distance, using early 1970s technology. Two of the major design goals of 3270's are related to this: minimizing the amount of data transmitted, and minimizing the frequency of interrupts to the mainframe.In a datastream, both text and control (or formatting functions) are interspersed allowing an entire screen to be "painted" as a single output operation. The concept of "formatting" in these devices allows the screen to be divided into clusters of contiguous character cells for which numerous "attributes" (colour, highlighting, character set, protection from modification) can be set. An attribute occupied a physical location on the screen which also determined the beginning and end of a "field" (separately addressable sub section of the screen).
Further, using a technique known as "read modified," a single transmission back to the mainframe can contain the changes from any number of formatted fields that have been modified, but without sending any unmodified fields or static data. This technique enhances the terminal throughput of the CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
, and minimizes the data transmitted. Some users familiar with character interrupt-driven terminal interfaces (such as Microsoft Windows) find this technique unusual. There was also a "read buffer" capability which transferred the entire content of the 3270-screen buffer
Screen buffer
In computing, screen buffer is a part of computer memory used by a computer application for the representation of the content to be shown on the computer display....
including field attributes. This was mainly used for debugging purposes to preserve the application program screen contents while replacing it, temporarily, with debugging information.
The first 3270s had no function keys. Later 3270s had twelve, and later twenty-four, special programmed function key
Function key
A function key is a key on a computer or terminal keyboard which can be programmed so as to cause an operating system command interpreter or application program to perform certain actions...
s, or PF keys, and three PA (or "program attention") keys placed in one or two rows at the top of the keyboard. When one of these keys is pressed, it will cause its control unit (historically, usually, an IBM 3274 or 3174, but nowadays the onboard mainframe equivalent) to generate an I/O interrupt and present a special code identifying which key was pressed. 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.
In this way, the CPU is not interrupted at every keystroke, a scheme which allowed an early 3033 mainframe with only 16 MB to support up to 17,500 3270 terminals under CICS
CICS
Customer Information Control System is a transaction server that runs primarily on IBM mainframe systems under z/OS and z/VSE.CICS is a transaction manager designed for rapid, high-volume online processing. This processing is mostly interactive , but background transactions are possible...
. On the other hand, vi
Vi
vi is a screen-oriented text editor originally created for the Unix operating system. The portable subset of the behavior of vi and programs based on it, and the ex editor language supported within these programs, is described by the Single Unix Specification and POSIX.The original code for vi...
-like behaviour was not possible. (But end-user responsiveness was arguably more predictable with 3270, something users appreciated.) For the same reason, a porting of Lotus 1-2-3
Lotus 1-2-3
Lotus 1-2-3 is a spreadsheet program from Lotus Software . It was the IBM PC's first "killer application"; its huge popularity in the mid-1980s contributed significantly to the success of the IBM PC in the corporate environment.-Beginnings:...
to mainframes with 3279 screens did not meet success because its programmers were not able to properly adapt the spreadsheet's user interface to a "screen at a time" rather than "character at a time" device.
In contrast, IBM's OfficeVision
OfficeVision
OfficeVision is an IBM proprietary office support application that primarily runs on IBM's VM operating system and its user interface CMS. Other platform versions are available, notably OV/MVS and OV/400...
office productivity software enjoyed great success with 3270 interaction because of its design understanding. And for many years the PROFS calendar was the most commonly displayed screen on office terminals around the world.
In contrast also, ICI
Imperial Chemical Industries
Imperial Chemical Industries was a British chemical company, taken over by AkzoNobel, a Dutch conglomerate, one of the largest chemical producers in the world. In its heyday, ICI was the largest manufacturing company in the British Empire, and commonly regarded as a "bellwether of the British...
Mond Division's Works Records System
Works Records System
The Works Records System , was an IBM mainframe based spreadsheet designed by Dr. Robert Mais, then an employee of ICI Mond Division in the UK and developed for the company to monitor chemical plant operations at Runcorn and elsewhere in the group...
, the first known shared public spreadsheet used the 3270 successfully for what was, in effect, a high powered version of today's spreadsheets with additional functions. It remained in continual use for 27 years up until 2001 and, despite its lack of a GUI
Gui
Gui or guee is a generic term to refer to grilled dishes in Korean cuisine. These most commonly have meat or fish as their primary ingredient, but may in some cases also comprise grilled vegetables or other vegetarian ingredients. The term derives from the verb, "gupda" in Korean, which literally...
, cells could be defined anywhere on the screen (not necessarily in rows or columns) and could be instantly re-configured for length, content and formulas as required. It is interesting to note that ICI's online, fully interactive system pre-dated PC spreadsheets by quite a few years and allowed multiple users to use the spreadsheets at the same time, similar to today's Web based shared spreadsheets.
As mentioned above, the Web (and HTTP
Hypertext Transfer Protocol
The Hypertext Transfer Protocol is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web....
) is similar to 3270 interaction because the terminal (browser) is given more responsibility for managing presentation and user input, minimizing host interaction while still facilitating server-based information retrieval and processing.
Applications development has in many ways returned to the 3270 approach. In the 3270 era, all application functionality was provided centrally. With the advent of the PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
, the idea was to invoke central systems only when absolutely unavoidable, and to do all application processing with local software on the personal computer. Now in the Web era (and with wikis in particular), the application again is strongly centrally controlled, with only technical functionality distributed to the PC.
In the early 1990s a popular solution to link PCs with the mainframes was the Irma board
Irma board
Irma board, originally spelled IRMA board, refers to a brand of coaxial interface cards for PCs and Macintosh computers used to enable 3270 emulator programs to connect to IBM mainframe computers....
. It was a piece of hardware that plugged into a PC and connected to a coaxial cable towards the mainframe. IRMA also allowed file transfers between the PC and the mainframe.
Third parties
Many manufacturers, such as Hewlett Packard, created 3270 compatible terminals, or adapted ASCII terminals such as the HP 2640HP 2640
The HP 2640A and other HP 264X models were block-mode "smart" and intelligent ASCII standard serial terminals produced by Hewlett Packard using the Intel 8008 and 8080 microprocessors.-History:...
series to have a similar block-mode capability which would transmit a screen at a time, with some form validation capability. Modern applications are sometimes built upon legacy 3270 applications, using software utilities to capture (screen scraping) screens and transfer the data to web pages or GUI interfaces.
Models
The IBM 3270 display terminal subsystem consisted of displays, printers and controllers.Displays
- 3277 model 1 : 40×12 terminal
- 3277 model 2 : 80×24 terminal, the biggest success of all
- 3277 model 3 : 80×32 terminal
- 3277 GA : a 3277 with an RS232C I/O, often used to drive a TektronixTektronixTektronix, Inc. is an American company best known for its test and measurement equipment such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. In November 2007, Tektronix became a subsidiary of Danaher Corporation....
4013 or 4015 graphic screen (monochrome) - 3278 models 3,4,5 : next-generation, with accented characters and dead keys in countries that needed them
- model 2 : 80×24
- model 3 : 80×32
- model 4 : 80×43
- model 5 : 132×27 or 80×24 (switchable)
- 3278 PS : programmable characters; able to display monochrome graphics
- 3279IBM 3279The IBM 3279 was IBM's first colour Terminal. It was introduced in 1979. The 3279 was widely used as an IBM mainframe terminal before PCs became commonly used for the purpose. It was part of the 3270 series, using the 3270 datastream...
: colour terminal, 4-colour (text) or 7-colour (graphics) version - 3290 : a large, monochrome plasma displayPlasma displayA plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...
unit, capable of displaying in various modes, including four independent 3278 model 2 terminals, or a single 160×62 terminal; it also supported partitioning.
- 3178 : lower cost terminal (1983)
- 3179 : low cost colour terminal (1984)
- 3104 : low-cost R-loop connected terminal for the IBM 8100IBM 8100See also: IBM 8000 series, canceled in 1961The IBM 8100 was at one time IBM’s principal distributed processing engine, providing local processing capability under two incompatible operating systems and was follow-on to IBM 3790....
system
(Generally, 3277 models were upper-case only, except for the mixed EBCDIC/APL which had lower case; lower-case capability and possibility of dead key
Dead key
A dead key is a special kind of a modifier key on a typewriter or computer keyboard that is typically used to attach a specific diacritic to a base letter. The dead key does not generate a character by itself but modifies the character generated by the key struck immediately after...
s, at first a simple RPQ (Request Price Quotation, tailored on request at extra cost) was only added in 3278 & 3279 models.)
A version of the IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
called the 3270 PC
IBM 3270 PC
The IBM 3270 PC , released in October 1983, was an IBM PC XT containing additional hardware which could emulate the behaviour of an IBM 3270 terminal...
, released in October 1983, included 3270 terminal emulation
Terminal emulator
A terminal emulator, terminal application, term, or tty for short, is a program that emulates a video terminal within some other display architecture....
. Later, the 3270 PC/G (graphics) and 3270 PC/GX (extended graphics) followed.
Display-Controller
- 3275 remote display with controller function (no additional displays and/or printers)
- 3276 remote display with controller function (up to a limited number of displays and/or printers)
Printers
- 3284 matrix printer
- 3286 matrix printer
- 3287 printer, including a color model
- 3288 line printer
- 3268-1 : R-loop connected stand-alone printer for the IBM 8100IBM 8100See also: IBM 8000 series, canceled in 1961The IBM 8100 was at one time IBM’s principal distributed processing engine, providing local processing capability under two incompatible operating systems and was follow-on to IBM 3790....
system
Controllers
- 3271 remote controller
- 3272 local controller
- 3274 cluster controller (different models could be channel-attached, BSC attached or SDLC attached, and had between eight and 32 co-ax ports)
- 3174 cluster controller
Manufacture
The IBM 3270 display terminal subsystem was architected and developed by IBM's KingstonKingston, New York
Kingston is a city in and the county seat of Ulster County, New York, USA. It is north of New York City and south of Albany. It became New York's first capital in 1777, and was burned by the British Oct. 16, 1777, after the Battles of Saratoga...
, NY, laboratory (which was later closed during IBM's difficult time in the mid-1990s). The printers were developed by the Endicott, NY, laboratory. As the subsystem expanded, the 3276 display-controller was developed by the Fujisawa
Fujisawa, Kanagawa
is a city located in Kanagawa, Japan. As of 2010, the city had an estimated population of 407,731 and a population density of 5,870 people per km². The total area is 69.51 km²-Geography:...
, Japan, laboratory, and later the Yamato
Yamato, Kanagawa
is a city located in central Kanagawa Prefecture, Japan. As of 2010, the city had an estimated population of 225,866 and a density of 8,320 persons per km². The total area was 27.06 km².-Surrounding municipalities:*Zama*Fujisawa*Ebina*Sagamihara*Ayase...
laboratory; and the 3279 color display and 3287 color printer by the Hursley
Hursley
Hursley is a village and civil parish in Hampshire, England with a population of around 800 in 2005. It is located roughly mid-way between Romsey and Winchester on the A3090...
, UK, laboratory. The subsystem products were manufactured in Kingston (displays and controllers), Endicott (printers), and Greenock
Greenock
Greenock is a town and administrative centre in the Inverclyde council area in United Kingdom, and a former burgh within the historic county of Renfrewshire, located in the west central Lowlands of Scotland...
, Scotland, UK, (most products) and shipped to users in U.S. and worldwide. 3278 terminals continued to be manufactured in Hortolandia, near Campinas
Campinas
Campinas is a city and municipality located in the coastal interior of the state of São Paulo, Brazil. is the administrative center of the meso-region of the same name, with 3,783,597 inhabitants as of the 2010 Census, consisting of 49 cities....
, 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.
Telnet 3270
Telnet 3270, or TN3270 describes either the process of sending and receiving 3270 data streams using the TelnetTELNET
Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communications facility using a virtual terminal connection...
protocol or the software that emulates a 3270 class terminal which communicates using that process. TN3270 allows a 3270 terminal emulator
Terminal emulator
A terminal emulator, terminal application, term, or tty for short, is a program that emulates a video terminal within some other display architecture....
to communicate over a TCP/IP
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
network instead of an SNA network. Standard telnet
TELNET
Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communications facility using a virtual terminal connection...
clients cannot be used as a substitute for TN3270 clients, as they use fundamentally different techniques for exchanging data.
See also
- 3270 emulator3270 emulatorA 3270 Emulator is a computer program that duplicates the functions of an IBM 3270 mainframe computer terminal on a PC or similar microcomputer....
- List of IBM products
- IBM 5250IBM 5250IBM 5250 was originally a family of terminal devices sold with the IBM System/34 minicomputer systems. One model was the IBM 5251-11. It also connected to the later System/36, System/38 and AS/400 systems.- Historical origins :...
display terminal subsystem for IBM AS/400
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