What Is Fortran?

Fortran, short for FORmula TRANslation, is one of the oldest high-level programming languages still in active use. It was designed from the outset to translate mathematical formulas directly into efficient machine instructions, which is why it became the default choice for scientists and engineers who needed raw numerical performance rather than general-purpose application features. Today it powers weather prediction systems, computational fluid dynamics solvers, and structural engineering software.

Fortran was developed at IBM by a team led by John Backus and first released in 1957 for the IBM 704 mainframe. It went through major revisions over the decades, FORTRAN 66 and 77 standardized the language across vendors, while Fortran 90 introduced free-form source code, modules, and array operations. Later standards, Fortran 95, 2003, 2008, 2018, and 2023, added object-oriented programming, coarrays for parallelism, and interoperability with C.

Despite being over sixty years old, Fortran remains embedded in critical scientific infrastructure. Numerical libraries such as LAPACK and BLAS, which underpin linear algebra in Python's NumPy and MATLAB, are written in Fortran. Weather and climate models used by agencies like NOAA and the European Centre for Medium-Range Weather Forecasts (ECMWF) still run on millions of lines of Fortran code, because the language's array semantics allow compilers to generate extremely fast, well-vectorized machine code.

Fortran's array syntax lets programmers express operations on entire arrays without explicit loops, for example writing C = A + B for whole matrices, and its strict aliasing rules mean the compiler can assume pointers do not overlap unless told otherwise. This gives Fortran compilers more freedom to auto-vectorize and parallelize code than equivalent C code, which is one reason it is still chosen for large-scale simulations in aerospace, nuclear physics, and genomics.