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The world's fastest supercomputers still spend enormous cycles executing Fortran. Born at IBM in 1957 as the first widely used high-level language, it never stopped evolving: modern Fortran (the 2018 standard, followed by Fortran 2023) has modules, derived types, whole-array operations, and built-in parallelism via coarrays — a very different beast from the punched-card FORTRAN 77 of legend. Weather forecasting at ECMWF and NOAA, climate models, computational chemistry codes, and the LAPACK/BLAS libraries underneath NumPy all run on it, compiled by the actively developed gfortran and flang. Engineering and physics programs still teach it for numerical methods. Here you can compile and run modern Fortran in a live terminal, typing values into read statements as the program executes.
program interactive_demo
implicit none
character(len=40) :: name
integer :: n, i
real, allocatable :: v(:)
write(*, '(a)', advance='no') 'What is your name? '
read(*, '(a)') name
print *, 'Hello, ', trim(name), '!'
write(*, '(a)', advance='no') 'How many squares to build? '
read(*, *) n
allocate(v(n))
v = [(real(i)**2, i = 1, n)] ! array constructor with implied do
print *, 'Squares:', v
print *, 'Sum =', sum(v)
print *, 'Mean =', sum(v) / n
end program interactive_demoFortran skills open doors in high-performance computing: national labs, weather and climate centers, aerospace CFD groups, and computational physics research all maintain large Fortran codebases and hire people who can read and modernize them. University numerical-methods courses in physics and engineering departments still assign Fortran for exactly this reason. Use this page to practice array syntax, do-loops, format descriptors, and allocatable arrays — or to test a subroutine's logic quickly before running it inside a large simulation where compile cycles are expensive.
Yes — list-directed read statements pause the program until you enter values in the terminal, and write output streams beforehand, so prompts show up first. Use advance='no' in the write format, as the example does, to keep the cursor on the prompt line like a classic console program.
Modern, free-form Fortran compiled with gfortran — you get modules, allocatable arrays, whole-array expressions, intrinsic functions like sum and matmul, and everything through the recent standards the compiler supports. Fixed-form F77 code generally still compiles too, since gfortran handles legacy sources, but new code should use free form.
External libraries like LAPACK and MPI aren't linkable in this single-file sandbox, and multi-node parallelism isn't meaningful in it. Intrinsic numerics (matmul, dot_product, random_number) work fine for algorithm development. The realistic workflow: validate your numerical logic here, then build with the full HPC stack on your cluster.
main.f90fortranread(*,*)program hello
implicit none
print *, 'Hello from Fortran!'
print *, 'Welcome to XCODX Online Compiler!'
end program hello