Printer Command Language

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Printer Command Language
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application/vnd.hp-PCL

Printer Command Language, more commonly referred to as PCL, is a page description language (PDL) developed by Hewlett-Packard as a printer protocol and has become a de facto industry standard. Originally developed for early inkjet printers in 1984, PCL has been released in varying levels for thermal, matrix, and page printers. HP-GL/2 and PJL are supported by later versions of PCL. [1]

Contents

PCL is occasionally and incorrectly said to be an abbreviation for Printer Control Language which actually is another term for page description language.

PCL levels 1 through 5 overview

PCL levels 1 through 5e/5c are command-based languages using control sequences that are processed and interpreted in the order they are received. At a consumer level, PCL data streams are generated by a print driver. PCL output can also be easily generated by custom applications.

PCL 6 overview

HP introduced PCL 6 around 1995 with the HP LaserJet 4000 series printers. [3] It consists of:

PCL 6 "Enhanced" architecture was altered to be more modular and to be more easily modified for future HP printers, that it prints complex graphics faster, that it reduces network traffic, and has higher quality. In early implementations, HP did not market PCL 6 well[ citation needed ], thus causing some confusion in terminology. PCL XL was renamed to PCL 6 Enhanced, but many third-party products still use the older term.

Some products may claim to be PCL 6 compliant, but may not include the PCL 5 backward compatibility. PCL 6 Enhanced is primarily generated by the printer drivers under Windows and CUPS. Due to its structure and compression methodology, custom applications rarely use it directly.

PCL 6 Enhanced is a stack-based, object-oriented protocol, similar to PostScript. However, it is restricted to binary encoding as opposed to PostScript, which can be sent either as binary code or as plain text. The plain-text commands and code examples shown in the PCL programming documentation are meant to be compiled with a utility like HP's JetASM before being sent to a printer.

PCL 6 Enhanced is designed to match the drawing model of Windows GDI. In this way, the Windows printer driver simply passes through GDI commands with very little modification, leading to faster return-to-application times. Microsoft has extended this concept with its next-generation XPS format, and printer implementations of XPS are being developed. This is not a new idea: it is comparable with Display Postscript and Apple's Quartz, and is in contrast to "GDI Printers" where a compressed bitmap is sent to the printer.

PCL 6 class revisions

Class 1.1

  • Draw tools: Support drawing lines, arcs/ellipses/chords, (rounded) rectangles, polygons, Bézier paths, clipped paths, raster images, scanlines, raster operations.
  • Color handling: Support 1/4/8-bit palettes, RGB/grey color space. Support custom halftone patterns (max 256 patterns).
  • Compression: Supports RLE.
  • Units of measurement: Inch, millimeter, tenth of millimeter.
  • Paper handling: Support custom or predefined sets of paper size, including common Letter, Legal, A4, etc. Can choose paper from manual feed, trays, cassettes. Paper can be duplexed horizontally or vertically. Paper can be oriented in portrait, landscape, or 180 degree rotation of the former two.
  • Font: Supports bitmap or TrueType fonts, 8 or 16-bit code points. Choosing character set uses different symbol set code from PCL 5. When bitmap font is used, many scaling commands are unavailable. When TrueType font is used, variable length descriptors, continuation blocks are not supported. Outline font can be rotated, scaled, or sheared.

Class 2.0

  • Compression: Added JPEG compression. A Proprietary variant of JPEG-like compression optimized for integer hardware called JetReady is used in a few HP Color Laserjet models (at the time of writing, 3 models, CLJ 3500, 3550, 3600). Those models require Class 3.0 inputs.
  • Paper handling: Media can redirected to different output bins (up to 256). Added A6 and Japanese B6 preset media sizes. Added Third cassette preset, 248 external tray media sources.
  • Font: Text can be written vertically.

Class 2.1

  • Color handling: Added Color matching feature.
  • Compression: Added Delta Row.
  • Paper handling: Orientation, media size are optional when declaring a new page. Added B5, JIS 8K, JIS 16K, JIS Exec paper sizes.

Class 2.2

  • Compression: Added JFIF.

Class 3.0

  • Color handling: Allow using different halftone settings for vector or raster graphics, text. Supports adaptive halftoning.
  • Protocol: Supports PCL passthrough, allowing PCL 5 features to be used by PCL 6 streams. However, some PCL 6 states are not preserved when using this feature.
  • Font: Supports PCL fonts.

JetReady printers (CLJ 3500/3550/3600) use undocumented extensions but otherwise mandate Class 3.0 inputs.

PJL overview

PJL (Printer Job Language) was introduced on the HP LaserJet IIIsi. PJL adds job level controls, such as printer language switching, job separation, environment commands, status feedback, device attendance and file system commands.

See also

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References

  1. PCL 5 Printer Language Technical Reference Manual (1st ed.). Hewlett-Packard Company. September 1990. HP Part No. 33459-90903.
  2. 1 2 3 4 5 Hewlett-Packard Co. (2013-10-29). "HP Support document - HP Support Center". Hewlett-Packard. Archived from the original on 2005-11-27. Retrieved 2014-03-10.
  3. "HP Color LaserJet and LaserJet Series Printers - History of Printer Command Language (PCL) - bpl04568 - HP Business Support Center". Hewlett-Packard. 2005-12-13. Archived from the original on 2005-11-27. Retrieved 2012-07-06.

Further reading