IBM 5250

IBM 5250

Company type	Terminal series
Industry	Computer hardware
Founded	1977
Headquarters	Armonk , United States
Products	Block-oriented terminals (5251 Display Station, 5252 Dual Display Station, 5256 Printer)

IBM 5250 denotes a series of block-oriented terminals that debuted alongside the IBM System/34 midrange computer platforms in 1977. These terminals also interface with subsequent systems such as the System/36, System/38, IBM AS/400, and IBM Power Systems running IBM i, in addition to the Series/1 minicomputer.

Components

5250 terminals can connect directly to the host system or communicate remotely through Synchronous Data Link Control (SDLC) at speeds reaching 9600bit/s. These devices support clustering and can be linked in a daisy-chain configuration. By 1980, the 5250 product line encompassed:

• 5251 Display Station: A monochrome text terminal offering either 12 lines of 80 characters (totaling 960 characters) or 24 lines of 80 characters (1920 characters). It supports both uppercase and lowercase letters, along with text attributes such as blinking, high intensity, reverse video, underline, and a distinctive column separator designed to enhance data entry efficiency.
• 5252 Dual Display Station: Equipped with two back-to-back 12-line CRT screens each paired with its own keyboard; this model was released following the original.
• 5256 Printer: A desktop serial dot matrix printer available in variants capable of printing at rates of 40, 60, or 120 characters per second, featuring a print line width of 132 characters.

5251/5252 format control

Field attributes govern data input types and behavior:

• Fields may be restricted to alphabetic characters, numeric only, or allow alphanumeric entries.
• Auto enter automatically triggers an ENTER key press upon field completion.
• Bypass causes the cursor to skip over designated fields without user input.
• Duplicate enable permits users to replicate the previous field’s content by pressing the DUP key.
• Field exit required enforces manual exit from the field before proceeding.
• Mandatory entry obligates users to provide input without skipping the field.
• Monocase converts any lowercase input into uppercase automatically.
• Mandatory fill requires that if any data is entered, the entire field must be completed.
• Right adjust aligns entered data to the right side of the field upon exit.
• Signed numeric reserves the last character position for indicating sign—blank for positive values and '-' for negative numbers.

Terminal status lights

The front panel of the 5251 terminal includes five indicator lights:

• System Available light: Illuminates when connected to the host system and data is being received.

• Message Waiting light: Alerts users to unread messages sent by others or system notifications; these appear after program termination or user login.

• Insert light: Signals that Insert Mode is active, causing newly typed characters to shift existing text rightward.

• Caps Lock light: Turns on when Caps Lock is engaged.

• Keyboard Shift light: Lights up while the Shift key is pressed.

Historical origins

The 5250 terminal represents a block-oriented design similar in concept but incompatible with the IBM 3270. Known for its sturdy construction, a typical 5251 unit weighs approximately , producing audible clicks reminiscent of electronic typewriters from its era.

Over time, enhancements to the 5250 data stream incorporated graphical user interface elements such as pop-up windows, checkboxes, option boxes, mouse interaction, and drop-down menus. The IBM 3180 model introduced support for seven colors—pink, red, blue, yellow, green, white, and turquoise—achieved through field attributes like blinking, high intensity, reverse image, and underlining. For instance, standard text appeared green; high intensity rendered white; blinking text showed red; underlined text was blue; column separators displayed yellow or turquoise with high intensity.

Currently, "5250" mainly refers to the underlying data stream protocol. The original hardware terminals with their bulky twinax cables have become obsolete but were once used as dedicated backup connections. Modern usage depends on PC or web-based terminal emulators that interpret and display 5250 data streams.

Telnet 5250

Telnet 5250 (TN5250) refers to both the encapsulation of 5250 data streams within the telnet protocol and software that emulates 5250 terminal interactions over TCP/IP networks, replacing traditional SNA connections. Unlike conventional telnet clients, TN5250 applications are designed to interpret the unique 5250 data stream format required for IBM iSeries communication.

Connecting 5250 terminals to standard hardware

A specialized interface was created to link directly to the Twinax port on a 5250 terminal, facilitating communication comparable to that of an AS/400 host system. This interface currently supports VT52 terminal emulation and grants shell access on the connected machine.

IBM 3179

Manufactured as both 3270 and 5250 terminal models.

IBM 3180

Produced in versions supporting both 3270 and 5250 terminals.

IBM 3196

Features an 80x24 character display. Available models:

• Model A10: Green monochrome screen
• Model B10: Amber-gold monochrome screen

IBM 3197

Offered in several variants:

• C10 and C20 with a capacity of 1920 characters
• D10 and D20 supporting 3564 characters
• D40 featuring a 15-inch green phosphor display

IBM 3477

Models include:

• HAX: 14-inch amber-gold monochrome display
• HGX: 14-inch green monochrome display
• HCX: 14-inch color display
• HDX: 15-inch green monitor

IBM 3486

Available models:

• BAX: 14-inch amber-gold screen
• BGX: 14-inch green screen

IBM 3487

Variants consist of:

• HAX: 15-inch amber-gold screen
• HCX: 14-inch color display
• HGX: 15-inch green screen

IBM 3488

Lacks an integrated display; designed to connect to an external monitor through VGA.

IBM 3489

No built-in display; connects externally via VGA interface.

See also

• Terminal emulator
• IBM 3270

External links

• Overview of the green screen (5250 Terminal)
• – TN5250 Telnet Interface details
• – Enhancements for TN5250 Telnet
• – IBM iSeries Telnet Improvements