Editing IBM 5250 (section)

==Components==
5250 devices can be directly attached to the [[Host (network)|host]] or communicate remotely using [[Synchronous Data Link Control]] (SDLC) at up to 9600bit/s.  Devices can also be clustered or [[Daisy chain (network topology)|daisy-chained]].
[[File:IBM 5251 terminal.jpg|thumb|IBM 5251 display station on front of [[IBM 5120]] system]]
In 1980 the 5250 system consisted of the following components:<ref>{{cite book|last=IBM Corporation|title=IBM 5250 Information Display System: IBM 5251 Display Station IBM 5252 Dual Display Station IBM 5256 Printer Introduction|year=1978|url=http://bitsavers.trailing-edge.com/pdf/ibm/5250_5251/GA21-9246-4_5250_Information_Display_System_Introduction_Jan80.pdf}}</ref>
* 5251 Display Station.  The monochrome text-only display can be either 960 characters, formatted as 12 lines of 80 characters, or 1920 characters as 24 lines of 80 characters. Upper and lower case is standard.  Text attributes consist of blink, high intensity, reverse video, non-display, underscore, and a unique ''column separator'' that causes the field to be preceded and followed by a vertical bar.  5251 and 5252 input ''format control'' attributes are optimized for data entry applications and offer significant enhancements over previous 3270 terminals.
* 5252 Dual Display Station.  The 5252 features a single [[cathode-ray tube|CRT]] displayed 12 lines each on two different sides back to back in a single case, with separate keyboards.  The 5252 was not part of the initial announcement.
* 5256 printer. The 5256 is a tabletop serial [[Dot matrix printing|dot matrix printer]] with three models providing speeds of 40, 60, or 120cps and a print line of 132 characters.

===5251/5252 format control===
[[Image:IBM 3486 terminal.jpg|thumb|IBM 3486 Terminal, a later terminal with 5250 functionality, capable of supporting two independent sessions concurrently, and with an [[amber screen]]. The keyboard is a 122-key variant of the [[Model_M_keyboard|Model M]]; the original 5251-1 had a much smaller beam-spring keyboard.<ref>[http://www.corestore.org/34.htm An IBM System/34]</ref>]]
Field attributes also define the type of data the operator can enter into a field, and specify other control information for the field.
* A field can be defined as alpha only, numeric only, or [[alphanumeric]].
*''Auto enter'' simulates an ''ENTER'' key press at the conclusion of the field.
*''Bypass'' automatically skips over a field in the screen.
*''Duplicate enable'' allows the operator to press the ''DUP'' key in a field, entering a special code which is interpreted by the application program – typically duplicating data in this field from the previous record or line.
*''Field exit required'' forces the operator to manually exit this field, rather than automatically advancing to the next field after entering the last character.
*''Mandatory entry'' specifies that the operator <u>must</u> enter data in this field and is not allowed to tab over it.
*''Monocase'' translates lower-case characters entered into this field to upper-case.
*''Mandatory fill'' specifies that this field must be entirely filled if any data is entered into it.
*''Right adjust'' will right adjust data entered in a field when the operator exits the field.
*''Signed numeric'' reserves the rightmost position of a field for a sign – blank for positive or '-' for negative.

===Terminal status lights===

On a 5251 type terminal featured five status lights on the front of the unit:

* ''System Available light'': If lit, this terminal is connected to the host system and is receiving information from it.

* ''Message Waiting light'': Other users, and the system itself, can send messages to [[workstation]]s. If lit, there is at least one message that has not been seen yet. When a program ends or when the user signs on, the message(s) will be shown.

* ''Insert light'': The [[Insert key]] has been pressed. Characters after the cursor will shift right when text is keyed. Press Insert again to cease Insert Mode.

* ''Caps Lock light'': The [[Caps Lock]] key has been pressed.

* ''Keyboard Shift light'': The [[Shift key]] is being pressed.