Date: 06 Feb 1997 00:00:01 EST

  If you're using IRIX 4.0.x, you should be using IDO 4.1.1.  It
  includes C 3.10.1 and the 3.12 back-end (the part of the compiler
  which actually produces the executable; 3.12 is the number you see
  when you use the 'file' command on an executable). The previous
  version was badly buggy; upgrade ASAP.

  IRIX 5.2 needs IDO 5.2, which includes C 3.18. Executables produced by
  the IRIX 5.x back-end don't show a version number with 'file', although
  this information can be obtained via 'odump -V'. 

  Each version of IDO has a corresponding version of Fortran, and they
  MUST be used together. IDO 4.1.1 needs Fortran 3.5.1 and IDO 5.2 needs
  Fortran 4.0.1. This is true for other languages as well, but only
  Fortran has confused enough people to have its version numbers here.

  Ping Huang <pshuang@sgi.com> adds:

  IRIX 5.3 needs IDO 5.3, IRIX 6.0 needs IDO 6.0, and IRIX 6.1 needs
  IDO 6.1; that's pretty easy.

  After that, IDO version numbers are no longer tightly coupled to the
  IRIX version number.  The first IDO for IRIX 6.2 was IDO 6.2, but
  then IDO 7.0 and IDO 7.0.1 came out for IRIX 6.2 as well.  And IDO
  7.1 comes in three different flavors: IDO 7.1 for IRIX 6.2, IDO 7.1
  for IRIX 6.3, and IDO 6.1 for IRIX 6.4.

  If you use IRIX 6.2, use IDO 7.1 for IRIX 6.2.  If you use IRIX 6.3
  or 6.4, the appropriate flavor of IDO 7.1 is your only choice (for now).