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F# was designed in 2005 at Microsoft Research by Don Syme. It's a functional-first language on .NET, heavily inspired by OCaml. Same runtime as C# — they share libraries.

The simplest program:

printfn "Hello, F#!"

That's it. No class, no Main, no namespace. F# scripts allow top-level expressions.

printfn is type-checked at compile time. The format string is parsed:

• %s for strings
• %d for ints
• %f for floats
• %A for any type (uses F#'s smart pretty-printer)
• \n already implied by printfn (the n)

printfn "%s is %d years old" "Ada" 36

F# is whitespace-significant. Indentation defines blocks (like Python). No braces, no semicolons.