# External Library Maintenance - avram - a virtual machine code interpreter
avram - a virtual machine code interpreter

### 3.9 External Library Maintenance

External mathematical library functions such as those documented in External Libraries that are invoked from virtual code by the `library` combinator (Library combinator) are also accessible from C by way of a uniform API implemented by the functions declared in `libfuns.h`. This interface applies even to libraries implemented in Fortran such as `minpack`. This section briefly documents the functions in `libfuns.h` and sets out some recommeded guidelines for developers wishing to add support for other external libraries.