Fortran Wiki
IFTRAN

IFTRAN is a structured extension of Fortran from the early 1970’s, similar in spirit to RATFOR. It was created by E. F. Miller at General Research Corporation, and was reimplemented at several other institutions, as a preprocessor:

“While the newer structured languages such as PASCAL are enjoying an unusual popularity, particularly in educational institutions, the workhorse language of scientists and engineers is still FORTRAN. FORTRAN can be argued for as the only truly transportable language; when going from site to site, FORTRAN is always expected to be available. Since this is not true of ALGOL, PASCAL, ADA or other structured languages, there is a good motivation for users and authors of code which may be transported to write in FORTRAN.”

http://nldr.library.ucar.edu/repository/assets/scdnewsletter/SCDN-000-000-000-020.pdf

https://github.com/yyr/ncl/tree/master/ncarg2d/src/libncarg/Iftran