Non User
Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z	Business Non User Industries Finance Tax

Home > Kernel (computer science)

5 Exokernels

Exokernels, also known as vertically structured operating systems, are a new and rather radical approach to OS design.

The idea behind this is to enable the developer to make all the decisions about hardware performance. Exokernels are extremely small, since they arbitrarily limit their functionality to the protection and multiplexing of resources.

Classic kernel designs (both monolithic and microkernels) abstract the hardware, hiding resources under a hardware abstraction layer, or behind device drivers. In these classic systems, if physical memory is allocated, one cannot assure its actual placement, for example.

The goal of an exokernel is to allow an application to request a specific piece of memory, a specific disk block etc., and merely ensure that the requested resource is free, and the application is allowed to access it.

Since an exokernel therefore only provides a very low-level interface to the hardware, lacking any of the higher-level functionalities of other operating systems, it is augmented by a "library operating system". Such a library OS interfaces to the exokernel below, and provides application writers with the familiar functionalities of a complete OS.

Some theoretical implications of an exokernel system are that it becomes possible to have several kinds of operating systems (Windows, Unix) running under a single exokernel, and that a developer may choose to override or increase functionality for performance reasons.

The concept of an exokernel has been around since at least 1995 [3], but as of 2004 the design is still very much a research effort and it is not used in any major commercial operating systems. One concept operating system is Nemesis , written by University of Cambridge, University of Glasgow, Citrix Systems, and the Swedish Institute of Computer Science . MIT has also built several exokernel based systems.

6 No-Kernel

7 See also

• Operating system
• Core
• Kernel (disambiguation)

8 External links

• Operating System Kernels at Sourceforge
• MIT Exokernel Operating System
• kernel image
• The KeyKOS Nanokernel Architecture, a 1992 paper by Norman Hardy et al.

Politics	Business	Finance

Topics: Kernel (computer Science) System Kernels Operating Monolithic...

---

KernelThe word kernel can mean more than one thing. The kernel of a seed is all that is within the outer coat of the seed, as the edible substance contained in the shell of a nut; hence, anything included in a shell, husk, or integument. The term kernel can als Kernel User Interface PackageKernel User Interface Package (KUIP) is the human interface to Physics Analysis Workbench (PAW). References . Kernel (algebra)Algebra In the various branches of mathematics that fall under the heading of abstract algebra, the kernel of a homomorphism measures the degree to which the homomorphism fails to be injective. The definition of kernel takes various forms in various conte Kernel (computer science)In computer science, the kernel is the fundamental part of an operating system. It is a piece of software responsible for providing secure access to the machine's hardware to various computer programs. Since there are many programs, and access to the hard Kernel (mathematics)The word kernel has several meanings in mathematics, some related to each other and some not. Kernels in algebra Kernels in abstract algebra are general constructions which measure the failure of a homomorphism or function to be injective. In set theory, Kernel (category theory)In category theory and its applications to other branches of mathematics, kernels are a generalization of the kernels of group homomorphisms and the kernels of module homomorphisms and certain other kernels from algebra. Intuitively, the kernel of the mor Kernel panic Kernel trick Kernel of a function Kernel (integral operator) Kernel Virtual Address Space Kernel (function) Kernel Scheduled Entities