# PetscFortranCallbackRegister
register a type+subtype callback. This is used by the PETSc Fortran interface to allow the use of user Fortran functions as arguments to PETSc functions that take function pointers 
## Synopsis
```
#include "petscsys.h"    
PetscErrorCode PetscFortranCallbackRegister(PetscClassId classid, const char *subtype, PetscFortranCallbackId *id)
```
Not Collective


## Input Parameters

- ***classid -*** ID of class on which to register callback
- ***subtype -*** subtype string, or NULL for class ids



## Output Parameter

- ***id -*** callback id





## See Also
 `PetscFortranCallbackGetSizes()`

## Level
developer

## Location
<A HREF="PETSC_DOC_OUT_ROOT_PLACEHOLDER/src/sys/objects/fcallback.c.html#PetscFortranCallbackRegister">src/sys/objects/fcallback.c</A>


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[Edit on GitLab](https://gitlab.com/petsc/petsc/-/edit/release/src/sys/objects/fcallback.c)


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