IBM 3270

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 possibility of dead keys, at first a simple RPQ (Request Price Quotation, tailored on request at extra cost) were only added in 3278 & 3279 models.

A version of the IBM PC called the 3270 PC, released in October 1983, includes 3270 terminal emulation. Later, the 3270 PC/G (graphics) and 3270 PC/GX (extended graphics) followed.

• 3277 model 1: 40×12 terminal
• 3277 model 2: 80×24 terminal, the biggest success of all
• 3277 GA: a 3277 with an RS232C I/O, often used to drive a Tektronix 4013 or 4015 graphic screen (monochrome)

• 3278 models 1–5: next-generation, with accented characters and dead keys in countries that needed them
  • model 1: 80x12
  • model 2: 80×24
  • model 2A: 80x24 (console) with 4 lines reserved
  • model 3: 80×32 or 80x24 (switchable)
  • model 4: 80×43 or 80x24 (switchable)
  • model 5: 132×27 or 80×24 (switchable)
• 3278 PS: programmable characters; able to display monochrome graphics

IBM 3279 Colour Display Terminal

An Informatics General computer programmer using an IBM 3279 terminal

The IBM 3279 was IBM's first colour[14] terminal. IBM initially announced four models, and later added a fifth model for use as a processor console.

• Models
  • model 2A: 80-24 base color
  • model 2B: 80-24 extended color
  • model 2C: 80-24 base color (console) with 4 lines reserved
  • model 3A: 80-32 base color
  • model 3B: 80-32 extended color
• Base color
  In base color mode the protection and intensity field attributes determine the color:

Base color mode

Protection	Intensity	Color
Unprotected	Normal	Green
Unprotected	Intensified	Red
Protected	Normal	Blue
Protected	Intensified	White

• Extended color
  In extended color mode the color field and character attributes determine the color as one of
  • Neutral (White)
  • Red
  • Blue
  • Green
  • Pink
  • Yellow
  • Turquoise

The 3279 was introduced in 1979.[15] 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 data stream.[16] from IBM. Terminals could be connected to a 3274 controller, either channel connected to an IBM mainframe or linked via an SDLC (Synchronous Data Link Control) link. In the Systems Network Architecture (SNA) protocol these terminals were logical unit type 2 (LU2). The basic model 2 used red, green for input fields, and blue and white for output fields. However, there were other models with seven colours and different screen sizes, and one kind had a loadable character set that could be used to show graphics.

The IBM 3279 with its graphics[lower-alpha 1] software support, Graphical Data Display Manager (GDDM), was designed at IBM's Hursley Development Laboratory, near Winchester, England.[17]

• 3290: a large, amber monochrome plasma display unit, capable of displaying in various modes, including four independent 3278 model 2 terminals, or a single 160×62 terminal; it also supported partitioning.[18][lower-alpha 2]

• 3178: lower cost terminal (1983)
• 3179: low cost colour terminal (1984)

The 3180 was a monochrome display, introduced on March 20, 1984, that the user could configure for several different basic and extended display modes; all of the basic modes have a primary screen size of 24x80. Modes 2 and 2+ have a secondary size of 24x80, 3 and 3+ have a secondary size of 32x80, 4 and 4+ have a secondary size of 43x80 and 5 and 5+ have a secondary size of 27x132. An application can override the primary and alternate screen sizes for the extended mode. The 3180 also supported a single explicit partition that could be reconfigured under application control.

The original 3192 was a monochrome display with the same characteristics as the 3180.

• 3104: low-cost R-loop connected terminal for the IBM 8100 system
• 3472 Infowindow

• 3275 remote display with controller function (no additional displays up to one printer)
• 3276 remote display with controller function (up to a limited number of displays or printers)

• 3284 matrix printer
• 3286 matrix printer
• 3287 printer, including a colour model
• 3288 line printer
• 3268-1 : R-loop connected stand-alone printer for the IBM 8100 system

• 3271 remote controller
• 3272 local controller
• 3274 cluster controller (different models could be channel-attached or remote via BSC or SDLC communication lines, and had between eight and 32 co-ax ports)
• 3174 cluster controller

By 1994 the "3174 Establishment Controller" supported features such as attachment to multiple hosts via token ring, Ethernet, or X.25 in addition to the standard channel attach or SDLC, and terminal attachment via twisted pair, token ring or Ethernet in addition to co-ax. They also support attachment of asynchronous ASCII terminals, printers, and plotters alongside 3270 devices.[19]

The IBM 3179G released in March 1984[21] is an IBM mainframe computer terminal providing 80×24 or 80×32 characters plus graphics.[22][23][24][25][26]

3179-G terminals combine text and graphics as separate layers on the screen. Although the text and graphics appear combined on the screen, the text layer actually sits over the graphics layer. The text layer contains the usual 3270-style cells which display characters (letters, numbers, symbols, or invisible control characters).[27] The graphics layer is an area of 720×384 pixels.[28] 'All Points Addressable' or 'vector graphics' is used to paint each pixel in one of sixteen colors. As well as being separate layers on the screen, the text and graphics layers are sent to the display in separate data streams, making them completely independent.

The G10 model is a standard 122-key typewriter keyboard, while the G20 model offers APL on the same layout. Compatible with IBM System/370, IBM 4300 series, 303x, 308x, IBM 3090, and IBM 9370.

The 3279g has a capability called "Extended Data Stream" (EDS). Documentation for the SAS software package says "The ability to do graphics on a 3270 terminal implies that it is an EDS device."[29]

The IBM 3472G has Native Vector Graphics capability.[27]

The following table shows the 3275/3277/3284/3286 character set for US English EBCDIC (optional characters were available for US ASCII, and UK, French, German, and Italian EBCDIC). The numbers are the equivalent Unicode code points.

On the 3275 and 3277 terminals without the a text feature, lower case characters display as uppercase. 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.[10]^:p.15

  Letter   Number   Punctuation   Symbol   Other   Undefined

Data sent to the 3270 consists of commands and orders. Commands instruct the 3270 control unit to perform some action on a specified device, such a read or write. Orders are sent as part of the data stream to control the format of the device buffer.

The following description applies to the 3271, 3272, and 3275 control units. Later models of 3270 have additional capabilities.

The data sent by Write or Erase/Write consists of the command code itself followed by a Write Control Character (WCC) optionally followed by a buffer containing orders or data (or both). The WCC controls the operation of the device. Bits may start printer operation and specify a print format. 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.

Orders consist of the order code byte followed by zero to three bytes of variable information.

The original 3277 and 3275 displays used an 8-bit field attribute byte of which five bits were used.[10]^:p.18

• Bits 0 and 1 are set so that the attribute will always be a valid EBCDIC (or ASCII) character.
• Bit 2 is zero to indicate that the associated field is unprotected (operator could enter data) or one for protected.
• Bit 3 is zero to indicate that this field, if unprotected, could accept alphanumeric input. One indicates that only numeric input is accepted, and automatically shifts to numeric for some keyboards.
• Bit 4 and 5 operate in tandem:
  • '00'B indicate that the field is displayed on the screen and is not selector-pen detectable.
  • '01'B indicates that the field is displayable and selector-pen detectable.
  • '10'B indicates that the field is intensified (bright), displayable, and selector-pen detectable.
  • '11'B indicates that the field is non-display, non-printable, and not pen detectable. This last can be used in conjunction with the modified data tag to imbed static data on the screen that will be read each time data was read from the device.
• Bit 7 is the "Modified Data Tag", where '0' indicates that the associated field has not been modified by the operator and '1' indicates that it has been modified. As noted above, this bit can be set programmatically to cause the field to be treated as modified.

Later models include base colour[33] "In base color mode, the protection and intensity bits are used in combination to select among four colors: normally white, red, blue, and green; the protection bits retain their protection functions as well as determining color."[34] Still later models used extended attributes to add support for seven colours, blinking, reverse video, underscoring, field outlining, field validation, and programmed symbols.[34] In addition, later models added character attributes, which could establish, e.g., color for individual characters without starting a new field or taking up a screen position.

3270 displays and printers have a buffer containing one byte for every screen position. For example, a 3277 model 2 featured a screen size of 24 rows of 80 columns for a buffer size of 1920 bytes. Bytes are addressed from zero to the screen size minus one, in this example 1919. "There is a fixed relationship between each ... buffer storage location and its position on the display screen."[10]^:p.13 Most orders start operation at the "current" buffer address, and executing an order or writing data will update this address. The buffer address can be set directly using the Set Buffer Address (SBA) order, often followed by Start Field. For a device with a 1920 character display a twelve bit address is sufficient. Later 3270s with larger screen sizes use fourteen or sixteen bits.

Addresses are encoded in orders in two bytes. For twelve bit addresses the high order two bits of each byte are normally set to form valid EBCDIC (or ASCII) characters. For example, address 0 is coded as X'4040', or space-space, address 1919 is coded as X'5D7F', or ')"'.[10]^:pp.75–90 Programmers hand coding panels usually keep the table of addresses from the 3270 Component Description or the 3270 Reference Card handy. For fourteen and sixteen bit address, the address uses contiguous bits in two bytes.

The following data stream writes an attribute in row 24, column 1, writes the (protected) characters '> ' in row 24, columns 2 and 3, and creates an unprotected field on row 24 from columns 5-79. Because the buffer wraps around an attribute is placed on row 24, column 80 to terminate the input field. This data stream would normally be written using an Erase/Write command which would set undefined positions on the screen to '00'x. Values are given in hexadecimal.

  Data        Description
  D3          WCC [reset device + restore (unlock) keyboard + reset MDT]
  11 5C F0    SBA Row 24 Column 1
  1D F0       SF/Attribute
              [protected, alphanumeric, display normal intensity, not pen-detectable, MDT off]
  6E 40       '> '
  1D 40       SF/Attribute
              [unprotected, alphanumeric, display normal intensity, not pen-detectable, MDT off]
              SBA is not required here since this is being written at the current buffer position 
  13          IC - cursor displays at current position: Row 24, column 5
  11 5D 7F    SBA Row 24 Column 80
  1D F0       SF/Attribute
              [protected, alphanumeric, display normal intensity, not pen-detectable, MDT off]