Printer Command Language

Printer Command Language. Printer Command Language is a page description language developed by Hewlett-Packard to control the features and output of its laser and inkjet printers. It has become a de facto standard in the printing industry, enabling complex document formatting and graphics. The language allows software applications to send detailed commands for text, fonts, and images to compatible printers.

Overview

Printer Command Language functions as an intermediary between a computer's operating system and a printer's hardware, interpreting high-level commands into precise raster images. It is most famously associated with the HP LaserJet series, which popularized desktop laser printing. The language supports a wide range of operations, from simple text printing to complex graphics rendering, making it versatile for both office and professional publishing environments. Its architecture allows for extensibility, with later versions adding support for advanced features like PostScript emulation and enhanced color management.

Technical specifications

The core of Printer Command Language is a command-set architecture where instructions are sent as plain ASCII text or binary data streams, often prefixed with an escape character. It utilizes a coordinate system based on decipoints for precise positioning of text and graphics on the page. Key technical components include its font handling, which supports both built-in bitmap fonts and scalable Intellifont and TrueType outlines, and its raster graphics model for compressing and printing image data. The language has evolved through versions like PCL 5 and PCL 6, with the latter introducing a more object-oriented structure for improved performance and support for the Windows GDI printing model.

Development and history

Printer Command Language was first introduced by Hewlett-Packard in 1984 alongside the original HP LaserJet printer, revolutionizing office printing by offering high-quality output at a relatively low cost. Early versions, such as PCL 1 through PCL 4, focused on basic text formatting and simple graphics. A major leap occurred with PCL 5 in 1990, which added scalable fonts and significantly enhanced graphics capabilities to compete with Adobe Systems' PostScript. The development of PCL 6 in the mid-1990s represented a complete redesign for the modern graphical user interface era, optimizing for the printing demands of Microsoft Windows and improving speed for complex documents.

Common commands and usage

Typical Printer Command Language commands control page formatting, font selection, and cursor positioning. For example, the Escape sequence "E" initiates a printer reset, while commands like "&l#E" set page margins. Font selection is commonly handled with commands specifying symbol sets like the PC-8 or Windows-1252 and pitch values. For graphics, the language uses raster compression techniques, such as run-length encoding, to transfer image data efficiently. In practice, these commands are generated automatically by printer driver software from applications like Microsoft Word or Adobe Acrobat, though they can also be embedded directly in print jobs for specialized control.

Related languages and protocols

Printer Command Language exists within a broader ecosystem of printing standards and competing technologies. Its primary historical competitor is PostScript, a more powerful but computationally intensive language from Adobe Systems. Many modern printers support both, with HP often implementing PCL PostScript emulation. Other related protocols include the Internet Printing Protocol for network-based printing and the Windows GDI print path, which PCL 6 was specifically optimized to complement. For color printing, languages like HP-GL/2 for plotters and the XML Paper Specification have also influenced the development of advanced Printer Command Language features.

Category:Page description languages Category:Hewlett-Packard Category:Printer Command Language Category:Printing