# Glossary¶

GUI
Graphical User Interface. This is a separate program that helps editing your input files and running the simulations. Every feature of PLaSK can be fully accessed without the GUI by manually editing its input files. However, the graphical interface offers a visual feedback while editing the structure geometry and provides hints for setting up your simulation.
Python
Python is a remarkably powerful dynamic programming language that is used in a wide variety of application domains. See: http://python.org/
shell
See: http://en.wikipedia.org/wiki/Command-line_interface
XPL
Standard extension of files that are used by PLaSK, a shortcut from “XML in PLaSK”
XML

Extensible Markup Language (XML) is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable.

In XML every element is described by tags, which are denoted by <…> brackets. Tags always have some name and may optionally contain some attributes and content. Attributes are always put together with the tag name inside the <…> brackets, i.e. <tag attr1="value1" attr2="value2">. On the other hand, the tag content is always put after the brackets and must end with the </tag> element. Inside the tag content you may put text or some other tags, depending on the kind of input you want (and more importantly may) to enter. If a tag does not have any content, this must be indicated by putting the / character before the closing bracket (i.e. <tag/>). Tag attributes are still allowed in such a case.

HDF5
HDF5 is a data model, library, and file format for storing and managing data. See: http://www.hdfgroup.org/HDF5/