Not really. They're just written in a way such that the memory layout is compatible with BLAS libraries — which are frequently written in Fortran. So they can be passed directly to functions that happen to have been written in Fortran.

Additionally, invoking BLAS/LAPACK only happens for dense arrays of specific types (single/double precision real/complex numbers). The great thing in Julia is that almost all of the array and linear algebra functionality is implemented completely generically, so that algorithms can be written using these higher-level concepts, and the low-level functionality will (very efficiently) dispatch to BLAS/LAPACK if possible; if not, the generic implementations still allow your algorithm to work for e.g. your user-defined number type.

haha yeah I guess i should have been more precise with my wording. I'm currently prototyping a custom number system in julia, and obviously, the multidimensional array ops will not be backended in BLAS.