MIRIAD was written with the intent that ``anybody'' should be able to re-program it. Most MIRIAD programs are implemented as a Fortran PROGRAM, calling a suite of subroutines from our MIRIAD library. Graphics is all done via the publicly available PGPLOT library, which comes with MIRIAD. A small part of the library is actually written in C, which implements all the lower level routines that read and write MIRIAD files. However, most of the ``astronomy'' is implemented in Fortran.
The most common scenario is when a program needs a small modification, for example, a write statement needs more digits, or an extra column.