gfortran-mod-12 software package provides virtual package provided by gfortran-4.9, gfortran, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gfortran-mod-12
gfortran-mod-12 is installed in your system.
Make ensure the gfortran-mod-12 package were installed using the commands given below,
$ sudo dpkg-query -l | grep gfortran-mod-12*
You will get with gfortran-mod-12 package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Virtual packages |
| Package | gfortran-mod-12 |
| Version | |
| Description | virtual package provided by gfortran-4.9, gfortran |
| Sub Section | virtual |