Real Inferno

Inferno is an operating system well suited to applications that need to be portable, graphical, and networked. This paper describes the fundamental oating point facilities of the system, including: tight rules on expression evaluation, binary/decimal conversion, exceptions and rounding, and the elementary function library. Although the focus of Inferno is interactive media, its portability across hardware and operating platforms, its relative simplicity, and its strength in distributed computing make it attractive for advanced scienti c computing as well. Since the appearance of a new operating system is a relatively uncommon event, this is a special opportunity for numerical analysts to voice their opinion about what fundamental facilities they need. The purpose of this short paper is to describe numerical aspects of the initial release of Inferno, and to invite comment before the tyranny of backward compatibility makes changes impossible. Overviews can be found at http://inferno.bell-labs.com/inferno/, but for our immediate purposes it may su ce to say that Inferno plays the role of a traditional operating system (with compilers, process control, networking, graphics, and so on) but can run either on bare hardware or on top of another operating system like Windows95 or Unix. Programs for Inferno are written in the language Limbo and compiled to machine-independent object les for the Dis virtual machine, which is then implemented with runtime compilation for best performance. Files are accessible over networks using the Styx protocol; together with the presentation of most system resources as les and the manipulation of le namespaces, this permits integration of a collection of machines into a team. Limbo looks somewhat like a mixture of C and Pascal, augmented by modules (to cope with the namespace and dynamic loading needs of large programs) and by a channel facility for convenient (coarse-grain) parallel programing. Array references are bounds-checked and memory is garbage collected. The rest of this paper covers the fundamental oating point environment provided by the Limbo compiler and math module, the \elementary functions,"