Fortran
The first widely used compiled language (1957), still standard in numerical and high-performance computing.
27 steps across 1 tours, from the basics to complete programs.
The tours
- First released
- 1957
- Created by
- John Backus's team at IBM
- Typing
- Static and explicit -- once implicit none switches the 1950s defaults off
- Snippets target
- Fortran 2023
- File extensions
- .f90, .f95, .f03, .f
What it is for
Fortran is where performance computing lives: weather forecasts, climate models, computational chemistry, aerodynamics, and a large share of what runs on the world's fastest machines. The linear algebra underneath NumPy and SciPy — BLAS and LAPACK — is Fortran, which means most Python data science calls it on every matrix multiply without knowing.
Arrays are the language's native tongue. A(2:5) slices, A * B multiplies elementwise, sum and maxval and where operate on whole arrays, and the compiler is free to vectorize and parallelize because the semantics were designed for it in 1990, not bolted on. Number crunching reads like the math it implements, and formula translation is literally the language's name.
Modern Fortran is a living language with an old reputation. Free-form source, modules, allocatable arrays, pure and elemental procedures, and native complex numbers arrived decades ago; coarrays put parallelism in the standard itself. The fortran-lang community ships a package manager (fpm), a standard library, and new compilers — while gfortran, which checks every seed here, remains the reliable workhorse.
Where it came from
In 1957 John Backus's team at IBM delivered the FORTRAN I compiler for the IBM 704, against the era's consensus that machine-generated code could never compete with hand-written assembly. It could. Formula translation cut program length by an order of magnitude, and scientific computing has never used anything else as its foundation.
FORTRAN 66 became the first language standard of any kind; FORTRAN 77 carried scientific computing for a generation of punch cards and fixed columns. Fortran 90 was the great modernization — free-form source, modules, recursion, and the whole-array operations that still distinguish the language — with 95, 2003 (objects), and 2008 (coarrays) building on it.
The 2010s brought a quiet revival: fortran-lang.org, the fpm package manager, the stdlib project, and new compilers (LFortran, LLVM's flang) alongside the long-lived gfortran. Fortran 2023 is the current standard. The codes it powers — weather, climate, materials, energy — are the ones civilization actually schedules supercomputer time for.
What it is like to type
Modern Fortran types in lowercase words with paired closers: program with end program, do with end do, if with end if. Declarations put the type first and the :: divider before the names, arrays use parentheses rather than brackets for indexing, and % reaches into derived types. The symbols cluster only in format strings and kind suffixes like 1.0_real64; the rest is steady, spelled-out words — comfortable middle-of-the-road typing.
27 steps across 1 tours, from the basics to complete programs.