Editing Line printer (section)

== Paper (forms) handling ==
[[File:IBM 1403 Printer opened.jpg|thumb|An IBM 1403 printer opened up as it would be to change paper. Note the form tractors on each side of the paper, and the carriage control tape in upper right. The print chain is covered by a full-width ink ribbon, see lower right: The hinged chain-and-ribbon assembly is here swung open towards the camera like a gate.]][[File:Green-zebra-paper.png|thumb|Green-zebra-paper]]
All line printers used [[Continuous stationery|continuous form paper]] provided in boxes of continuous [[fan-fold]] forms rather than cut-sheets. The paper was usually [[Perforation|perforated]] to tear into cut sheets if desired and was commonly printed with alternating white and light-green areas, allowing the reader to easily follow a line of text across the page. This was the iconic <span id="green bar paper">"'''green bar'''"</span>, "blue bar" or "music-ruled" form paper that dominated the early computer age in several variants. Standard "green bar" page sizes included [[portrait format|portrait-format]] pages of 8½ × 11 inches ([[letter size]]), usually printed at 80 columns by 66 lines of characters (at 6 lines per inch) or 88 lines (at 8 LPI), and [[landscape format|landscape-format]] pages of 14 × 11 inches, usually printed at 132 columns by 66 or 88 lines. Also common were landscape-format pages of 14 × 8½ inches ([[legal size]]), allowing for 132 columns by 66 lines (at 8 LPI) on a more compact page.

Pre-printed forms were also commonly used (for printing [[cheque]]s, [[invoice]]s, etc.). A common task for the system operator was to change from one paper form to another as one print job completed and another was to begin. Some line printers had covers that opened automatically when the printer required attention. These continuous forms were advanced through the printer by means of ''tractors'' ([[sprocket]]s or sprocket belts). Depending on the sophistication of the printer, there might simply be two tractors at the top of the printer (pulling the paper) or tractors at the top and bottom (thereby maintaining paper tension within the printer). The horizontal position of the tractors was usually adjustable to accommodate different forms. The earliest printers by IBM used a hydraulic motor to move the forms. In later line printers, high-speed [[servomechanism]]s usually drove the tractors, allowing very rapid positioning of the paper, both for advancing line-by-line and slewing to the top of the next form. The faster line printers, of necessity, also used "stackers" to re-fold and stack the fan-fold forms as they emerged from the printer.

The high-speed motion of the paper often developed large [[Electrostatics|electrostatic]] charges. Line printers frequently used a variety of discharge [[brush]]es and active ([[corona discharge]]-based) static eliminators to discharge these accumulated charges.

Many printers supported [[ASA carriage control characters]]{{citation needed|date=December 2011}} which provided a limited degree of control over the paper, by specifying how far to advance the paper between printed lines. Various means of providing vertical tabulation were provided, ranging from a paper [[carriage control tape]] loop to fully electronic (software-controllable) tab simulation.