WebAssembly.wat

(module
    (import "wasi_unstable" "fd_write"
        (func $fd_write (param i32 i32 i32 i32) (result i32))
    )

    (memory 1)
    (export "memory" (memory 0))

    (data (i32.const 0) "\08\00\00\00\0c\00\00\00Hello World\n")

    (func $main (export "_start")
        i32.const 1
        i32.const 0
        i32.const 1
        i32.const 20
        call $fd_write
        drop
    )
)