Operating system core

an operating system core or a system core (English. kernel [ˈkɜːɹnl]) is the central component of an operating system. In it the process and data organization are fixed, on which all further software components of the operating system develop. The construction of a stable operating system core is oneTask from the range of computer science and software engineering.

Usual requirements of a system core are parallel processing of different tasks (multitasking), adherence to time-critical borders, openness for most different applications and extensions.

Example: Linux Kernel, of Linus Torvalds 1991 provides andsince then as open SOURCE - project world-wide develops further.

To table of contents

components

a system core is developed in layers, whereby the lower (more machine-oriented) layers the basisfor the upper (machine-further) layers form. The upper layers can call the functions of the lower layers, but in reverse.


The following layers are present (from bottom to top):

if all these functions in the system core are present, speak one of a monolithic Kernel. At a Mikrokernel substantial parts during separate processes take place. Besides,and/or. between both lying, there are still the so-called Makrokernel.

In any case ones outside of the Kernels run the user processes, which avail themselves of the functions offered by the Kernel, in order to communicate with the machine.

tasksa Kernels

a Kernel has the following tasks:

  1. Interface to user programs (start, a terminating, input/output, memory access)
  2. control of the access to processor, devices, memory (scheduler, device driver, storage protection). As exclusive an accesses of the Kernels to these resources as possible.
  3. Distribution of resources, for instance the processor time (EN)(and/or. the processors) on the user programs
  4. structuring of resources, about illustration of file systems on block oriented devices such as non removable disks, network minutes piles on network maps.
  5. Dissolution of access conflicts, about bolting device with multiprocessor systems, queues with scarce resources
  6. Virtualisierung of resources (processor: Processes, non removable disk: Files,Network map: z. B. Sockets, memory: virtual memory, devices: Special files)
  7. monitoring of rights of access on files and devices with time sharing systems

of processes

for the realization of an operating system the concept of a process (or also a task) is often used. A process contains(at least) a register record of the processor and can be continued over the scheduler and started again. Each process has beside it controlled access to a part of the memory as well as in and output channels, which access files or devices. With the Kernel communicatesit over system calls. A user program normally runs in exactly one, in exceptional cases also in several processes. Also some system services run within processes.

starting

when starting of a computer becomes after a possible hardware check and a partial equipment initializationthe Kernel loaded into the memory and started. It initialize the devices completely and start the first process. With simple systems such as MS-DOS this is a command line interpreter, with multi-process systems a certain process (with Linux/Unix INIT), that the system services(as processes) loads and again, possibly. after input of names and password, starts one or more command interpreters or a graphic user surface as processes. Afterwards it takes over a starting/a stopping of further processes (user programs) with the help of the system calls as well as the dispatching ofMemory and in/output channels on the individual processes.

Kernelarten

ability on a Kernel several processes run at the same time, speak one of multitasking cores. If a multitasking Kernel is supplemented by an access administration on processes and devices, one receives a multi-user (or multi-user) to system. On thatcan several users work at the same time. Each user must log in (Authentifizierung). The Kernel assigns each process a user, each user can however several processes possess. Dependent on the user procedural laws are limited. The Kernel is for the Separation of the processesand thus the user responsibly.

Although today's Desktopsysteme is used at the same time usually only by a user, they are laid out as time sharing system. This not only because then several users with own in each case preferences can use the system. Additionallythe system services among anonymous users are started. Thereby own, reduced rights of access can be granted to each system service and each user, which are necessary for the work. The system security is drastically increased thereby.

see also

 

  > German to English > de.wikipedia.org (Machine translated into English)