To provide printing on different printers with a common command set, Hewlett-Packard developed a language for printer control called "Printer Command Language" (PCL). Hewlett- Packard's PCL defines a standard for printer features and feature access by software applications. It provides the highest level of communication between the system and the printer. PCL is designed to be independent of the host system, device drivers, I/O interface, and network communications. Its purpose is to bring together all Hewlett-Packard printers under a common and consistent control structure that provides feature compatibility from printer to printer. This protects investment in applications and driver software. The key to designing PCL was determining the printing features for the various printer markets. Due to the diversity of printing needs from the low-end personal computer market to the high-end computer market, developing a common feature set would have either restricted the advanced printing capabilities of high-end printers or added to the cost of the low-end printers. The solution was simple: design PCL by partitioning printer features so they align with the major printer markets.
The PCL printer language has evolved through five major levels of functionality driven by the combination of printer technology developments, changing user needs, and application software improvements.
The five phases of the PC printer language evolution are:
PCL 1 Print and Space functionality is the base set of functions provided for simple, convenient, single-user workstation output.
PCL 2 EDP (Electronic Data Processing) /Transaction functionality is a superset of PCL 1. Functions were added for general purpose, multi-user system printing.
PCL 3 Office Word Processing functionality is a superset of PCL 2. Functions were added for high-quality, office document production.
PCL 4 Page Formatting functionality is a superset of PCL 3. Functions were added for new page printing capabilities.
PCL 5 Office Publishing functionality is a superset of PCL 4. New publishing capabilities include font scaling and HP-GL/2 graphics.
The PCL model succeeds because the following points are observed:
All PCL printers implement features consistently.
Each level is a proper subset of the previous level.
All PCL printers have the ability to ignore most unsupported commands.