The paper presents a new model for performing input/output (I/O) in a non-strict, purely functional language using monads. This model is composable, extensible, efficient, and does not require extensions to the type system. It smoothly extends to incorporate mixed-language working and in-place array updates. The authors compare this monadic approach with other standard approaches, such as dialogues and continuations, and discuss the implementation details, including the use of unboxed data types and code generation techniques. They also explore extensions to the IO monad, such as delayed I/O, asynchronous I/O, and assignment and reference variables. The paper concludes with a discussion of related work, including effect systems and linear types, and outlines future research directions.The paper presents a new model for performing input/output (I/O) in a non-strict, purely functional language using monads. This model is composable, extensible, efficient, and does not require extensions to the type system. It smoothly extends to incorporate mixed-language working and in-place array updates. The authors compare this monadic approach with other standard approaches, such as dialogues and continuations, and discuss the implementation details, including the use of unboxed data types and code generation techniques. They also explore extensions to the IO monad, such as delayed I/O, asynchronous I/O, and assignment and reference variables. The paper concludes with a discussion of related work, including effect systems and linear types, and outlines future research directions.