  CASA, the Common Astronomy Software Applications, is the primary data
processing software for the Atacama Large Millimeter/submillimeter Array (ALMA)
and the Karl G. Jansky Very Large Array (VLA), and is frequently used also for
other radio telescopes. The CASA software can handle data from single-dish,
aperture-synthesis, and Very Long Baseline Interferometery (VLBI) telescopes.
One of its core functionalities is to support the calibration and imaging
pipelines for ALMA, VLA, VLA Sky Survey (VLASS), and the Nobeyama 45m
telescope. This paper presents a high-level overview of the basic structure of
the CASA software, as well as procedures for calibrating and imaging
astronomical radio data in CASA. CASA is being developed by an international
consortium of scientists and software engineers based at the National Radio
Astronomical Observatory (NRAO), the European Southern Observatory (ESO), the
National Astronomical Observatory of Japan (NAOJ), and the Joint Institute for
VLBI European Research Infrastructure Consortium (JIV-ERIC), under the guidance
of NRAO.
