Printer Command Language

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 printer, and page printers. HP-GL and PJL are supported by later versions of PCL.

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.

Phosphorus pentachloride

Phosphorus pentachloride is the chemical compound with the formula PCl₅. It is one of the most important phosphorus chlorides, others being PCl₃ and POCl₃. PCl₅ finds use as a chlorinating reagent. It is a colourless, water- and moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

Structure

The structures for the phosphorus chlorides are invariably consistent with VSEPR theory. The structure of PCl₅ depends on its environment. Gaseous and molten PCl₅ is a neutral molecule with trigonal bipyramidal (D_3h) symmetry. The hypervalent nature of this species (as well as for PCl−
6, see below) can be explained with the inclusion of non-bonding MOs (Molecular orbital theory) or resonance (Valence bond theory). This trigonal bipyramidal structure persists in non-polar solvents, such as CS₂ and CCl₄. In the solid state PCl₅ is ionic, formulated PCl+
4PCl−
6.

In solutions of polar solvents, PCl₅ undergoes "autoionization". Dilute solutions dissociate according to the following equilibrium: