qgraf is a computer program that can generate Feynman diagrams and represent them by symbolic expressions; no graphical representation is generated, though. It was written to assist in large perturbative calculations, in the context of Quantum Field Theory.

• Programming language: FORTRAN 77 (there should be some evolution in the next major release).
  Binaries/executables are not distributed; the program has to be compiled and linked, eg with GNU's gfortran.
  Please report any error you may happen to find.

• Latest version: qgraf-3.3 (July 2018).
  The features added since the release of version 3.1.4 include:
  increased performance in some ‘extreme’ cases (3.1.5);
  option “onshellx”, an extended form of “onshell” (3.2);
  a way of restricting the configuration of external lines (3.3);
  the ability to require/disallow bridge-type propagators with certain momenta (3.3);
  improved treatment of duplicate vertices (3.3).

• A note to software developers:
  qgraf-3.4, which should be available by the end of 2018, will be the next ‘stable’ version
  (ie available for a long period, minimal fixes if need be).

The diagram generation is based on the algorithm described in the following article:

• Automatic Feynman graph generation
  P. Nogueira
  J. Comput. Phys. 105 (1993) 279-289
  https://doi.org/10.1006/jcph.1993.1074