This reference manual contains information about Tempo commands, options, file formats, and so forth. It is not intended to be an introduction to Tempo for new users or a treatise on pulsar timing. ... The document is in ASCII format. It may be downloaded as one long file, or as individual sections. ... Input file . Free-format header . ... Output files . Configuration file (tempo.cfg) . Clock correction files . ... Barycenter time correction . ... parameter files . ...