Abaqus has many built-in options but sometimes these do not suffice. You may want to include a material model that is not implemented, have a complex type of loading that is not available by default or even define your own element. Abaqus' user subroutine capabilities allow you to do this. User subroutines are written in Fortran and in order to use them, you need a Fortran compiler. In this blog I'll show how to install a freely available fortran compiler and link it to Abaqus. Thanks to Oliver Lundqvist working for Sweco in Finland for making me aware of this option, and to oaeres on https://community.intel.com/t5/Registration-Download-Licensing/How-to-link-ABAQUS-with-Intel-One-API-toolkits-to-run-FORTRAN/td-p/1244548/page/2 who provided this solution (especially the last workaround).