PAT is a portable atlas. It does what a traditional paper atlas does, but interactively: you can list country information using the included World Factbook ("list australia"), and draw world and country maps with the included World Databank of coastlines, rivers, and political and other boundaries ("select france; add france, fill white"). PAT is designed for the beginning user and its self-documenting command language ("add ?") is as simple and direct as possible (do "help").

PAT runs in batch mode using a command-line interface (CLI) and scripts, or interactively with its simple GUI (left click to set origin and center window, drag left to continuously change origin; zoom, pan, etc). An API lets the PAT library be incorporated into other programs. PAT is multilingual (messages in English and French so far), uses Unicode (UCS2) internally, and comes with Unicode fonts.

PAT's design goal is maximum portability: it wants to run on any machine and produce maps, even if they're only ASCII art! To that end, it's written in ANSI C, since C is a mature, stable language and most modern systems have ANSI C compilers and ISO compliant runtime libraries. PAT has a bare minimum of operating system dependencies, and runs on Unix (including GNU/Linux) and DOS (so far).

PAT uses an abstract raster device model. Device drivers are included for text, curses, GIF, JPEG, PNG, plain binary raster, X11, XBM, and GRX (for DOS). It can parse a variety of plain-text data formats, and load E00 (ArcInfo export) and Shapefiles. PAT has 50 built-in displays which don't rely on external data, and >70 projections. PAT is extensible: adding new systems, projections, devices, displays, fills, and shades is easy.

In order to test PAT's fitness for the purpose, I have used it to draw many world, regional, country and state maps; these are part of the test suite now, and the maps themselves I have placed in the public domain.