We describe a monadic interface to low-level hardware features that is a suitable basis for building operating systems in Haskell. The interface includes primitives for controlling memory management hardware, user-mode process execution, and low-level device I/O. The interface enforces memory safety in nearly all circumstances. Its behavior is specified in part by formal assertions written in a programming logic called P-Logic. The interface has been implemented on bare IA32 hardware using the Glasgow Haskell Compiler (GHC) runtime system. We show how a variety of simple O/S kernels can be constructed on top of the interface, including a simple separation kernel and a demonstration system in which the kernel, window system, and all device drivers are written in Haskell.

We describe a monadic interface to low-level hardware features that is a suitable basis for building operating systems in Haskell. The interface includes primitives for controlling memory management hardware, user-mode process execution, and low-level device I/O. The interface enforces memory safety in nearly all circumstances. Its behavior is specified in part by formal assertions written in a programming logic called P-Logic. The interface has been implemented on bare IA32 hardware using the Glasgow Haskell Compiler (GHC) runtime system. We show how a variety of simple O/S kernels can be constructed on top of the interface, including a simple separation kernel and a demonstration system in which the kernel, window system, and all device drivers are written in Haskell.

We introduce the <i>Deductive Verificaton Framework</i> (DVF), a language and a tool for verifying properties of transition systems. The language is procedural and the system transitions are a selected subset of procedures. The type system and built-in operations are consistent with SMT-LIB, as are the multisorted first-order logical formulas that may occur in DVF programs as pre- and post-conditions, assumptions, assertions, and goals. A template mechanism allows parametric specification of complex types within the confines of this logic. Verification conditions are generated from specified goals and passed to SMT engine(s). A general assume-guarantee scheme supports a thin layer of interactive proving.

In a previous paper (Leslie (1967)) the distribution of recurrence times for a particular set of success-failure patterns on a sequence of Bernoulli trials was investigated. We now consider the analogous events in continuous time and obtain the Laplace Transform (L.T.) of the distribution of recurrence times; numerical inversion yields the distribution functions.

This paper explains how the high-level treatment of datatypes in functional languages-using features like constructor functions and pattern matching-can be made to coexist with bitdata. We use this term to describe the bit-level representations of data that are required in the construction of many different applications, including operating systems, device drivers, and assemblers. We explain our approach as a combination of two language extensions, each of which could potentially be adapted to any modern functional language. The first adds simple and elegant constructs for manipulating raw bitfield values, while the second provides a view-like mechanism for defining distinct new bitdata types with fine-control over the underlying representation. Our design leverages polymorphic type inference, as well as techniques for improvement of qualified types, to track both the type and the width of bitdata structures. We have implemented our extensions in a small functional language interpreter, and used it to show that our approach can handle a wide range of practical bitdata types.