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Fortran is one of the oldest high-level programming languages, originally created for numerical and scientific computing, and it remains a mainstay of high-performance and engineering codes. It offers native multidimensional arrays, strong support for floating-point math, and modern features from array slicing to modules and procedures. CompileBytes compiles Fortran with gfortran, the GNU Fortran compiler; the reported version 10.2.0 reflects the GCC toolchain.
Modern Fortran (Fortran 90 and later) replaced fixed-form punched-card layout with free-form source, modules for encapsulation, and powerful array operations that let you express whole-array computations concisely. Programs begin with a program block and end with end program. Thanks to mature optimizing compilers and decades of tuned numerical libraries, Fortran continues to power simulations in physics, climate modeling, and computational engineering.
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program hello
print *, "Hello, World!"
end program helloprogram main
implicit none
print *, square(7)
contains
integer function square(n)
integer, intent(in) :: n
square = n * n
end function square
end program mainprogram loop
implicit none
integer :: i
do i = 1, 5
print *, i, i * i
end do
end program loopprogram arrays
implicit none
integer :: a(5) = [1, 2, 3, 4, 5]
integer :: b(5)
b = a * a
print *, "squares:", b
print *, "sum:", sum(a)
end program arraysprogram grade
implicit none
integer :: score = 75
if (score >= 90) then
print *, "A"
else if (score >= 70) then
print *, "B"
else
print *, "C"
end if
end program gradeprogram readinput
implicit none
integer :: n
print *, "Enter a number:"
read *, n
print *, "Doubled:", n * 2
end program readinputprogram main
implicit none
integer :: result
call add(3, 4, result)
print *, "sum:", result
contains
subroutine add(a, b, c)
integer, intent(in) :: a, b
integer, intent(out) :: c
c = a + b
end subroutine add
end program mainprogram main
implicit none
print *, factorial(5)
contains
recursive function factorial(n) result(f)
integer, intent(in) :: n
integer :: f
if (n <= 1) then
f = 1
else
f = n * factorial(n - 1)
end if
end function factorial
end program mainprogram fmt
implicit none
real :: pi = 3.14159265
integer :: count = 42
write(*, '(A, F6.3)') "pi = ", pi
write(*, '(A, I4)') "count = ", count
end program fmtThe editor uses Monaco, the engine behind VS Code, with language-aware editing tools and familiar keyboard controls.
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Fortran is one of 46 single-file compiler scratchpads. Each run submits only main.f90; local sibling-file imports are not enabled.
Linked-project languages (23): Node.js, TypeScript, Deno, Python, C, Go, Dart, Swift, Rust, Ruby, PHP, Java, Kotlin, C++, C#, Nim, Crystal, Haxe, Zig, Scala, D, Bun, Objective-C.
Single-file scratchpads (46): Matplotlib, NumPy, pandas, Haskell, Clojure, Perl, Lua, Tcl, jq, Raku, Elixir, Bash, Zsh, Nushell, R, Assembly (NASM), Julia, Octave, Groovy, PowerShell, Visual Basic .NET, Odin, Pascal, Lisp, Erlang, CoffeeScript, COBOL, BASIC, V, Racket, OCaml, Prolog, AWK, Emacs Lisp, Emojicode, Forth, F#, Fortran, Assembly (NASM64), Solidity, Mojo, Ada, WASM (WAT), Gleam, Shell Script (sh), Scheme.
Download file exports the active Fortran source file.