## Chapter 31: User Routines

User routines are Fortran subroutines (User CEL Functions, Junction Box Routines, and Particle User Routines) that you write for the CFX-Solver. You use the User Routine details view to create objects that link your Fortran subroutines to the CFX-Solver. To access the User Routine details view, either select Insert > Expressions, Functions and Variables > User Routines or click Insert User Routine in the main toolbar.

Once your User Routines have been created and linked, they appear in the tree view under Simulation > Expressions, Functions and Variables > User Routines.

## User Routine Details View

The User Routine details view creates objects that link your Fortran subroutines to the CFX-Solver.

There are four types of user routines:

- User CEL Routines

- Junction Box Routines

- Particle User Routines

- For details on the fourth user-routine option, `Transient Particle Diagnostics Routine`, refer to User Diagnostics Routine in the CFX-Solver Modeling Guide.

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