.f90 File — Fortran 90+ Source

F90 files contain source code written in Fortran 90 or later versions (Fortran 95, 2003, 2008, 2018) using free-form source format. Fortran (Formula Translation) is the oldest high-level programming language still in active use, created at IBM by John Backus in 1957. Modern Fortran (90+) is dramatically different from its FORTRAN 77 predecessor — it supports free-form source layout, modules, derived types (structs), array operations, pointers, dynamic memory allocation, operator overloading, abstract interfaces, and object-oriented programming with type extension and polymorphism. Fortran remains the dominant language in high-performance scientific computing, weather/climate modeling, computational fluid dynamics, molecular dynamics, and numerical linear algebra. The language's array-oriented syntax and mature optimizing compilers (gfortran, ifort, nvfortran) produce exceptionally efficient code for numerical computations, often outperforming C and C++ for array-intensive workloads. The BLAS, LAPACK, and FFTW libraries that underpin NumPy, MATLAB, and most scientific computing ecosystems are written in Fortran. Fortran's coarray feature provides built-in parallel programming capabilities for distributed computing.