PCL5e is an escape-based language usually interpreted immediately when it arrives at the printer, while PCL6 is a structured language and is first compiled before it’s interpreted and sent to the printer. PCL5e is an enhanced version of PCL5.
Both PCL5e and PCL6 are HP printer language drivers, and while they both hold the PCL title, they operate completely differently. PCL5e and versions before it send commands and data to the printers via ASCII code. PCL5e improved on PCL5 by offering a wider range of font options and also introduced bidirectional communication between the computer and printer.
PCL6 however, operates by compiling the commands and data into a binary format before sending them to the printer. The binary formats output a much smaller and compressed version and allows this language to offer additional features and faster operation. PCL6 drivers can handle much more complex graphics than the PCL5e drivers, and they also offer a higher resolution than 300 dpi, which is the maximum for PCL5e.
The PCL5e drivers are designed to be completely backward compatible, possessing all the commands of previous drivers. PCL6 drivers are also backward compatible. However, their unique structure makes its compatibility somewhat buggy, causing more people to lean towards the PCL5 drivers.