Operating system

an operating system is the software, which makes the use possible (the enterprise) of a computer. It administers operational funds such as memory, in and output devices and steers the execution of programs.

Operating system is called on English operating system (OS). This English expressionmarks the sense and purpose: In the beginnings of the computers strongly with schematic and errorpregnant work employed operators wrote programs, in order to facilitate itself the work; these were combined gradually into the operating system.

Operating systems exist inthe rule from a core (English:Kernel), which administers the hardware of the computer, as well as fundamental system programs, which serve the start of the operating system and its configuration.

Differences become a user and time sharing systems, individual program and multi-program systems, batch processing and conversational time sharings. Operating systems finditself in nearly all computers: as real time processing systems on process computers, on normal PCs and as multiprocessor systems on servers and large computers.

Table of contents

kinds of operating system

operating systems being able as the directResult of the underlying system and the tasks which can be fulfilled to be regarded. Therefore it is to be likewise concerned essential apart from the different systems with the associated systems.

Punch cards belong meanwhile to the past. However are the so-called batch systems (English. batch of system, queued system) a good beginning for the view of the system development. These enormous systems were served said by only one person - the operator - or fed better. Programmers made punch cards and handed the card deck to the operator over.This let the maps of the machine read in and handed to the programmers out afterwards the results in printed out form. These machines did not possess a conventional operating system, as it is common today. Only a supervisory routine (resident monitor) became in the memoryheld and providing for the smooth operational sequence by control to the programs momentarily which can be implemented handed over.

An advancement - Multiprogrammed batch system - could hold now at least several programs and data in the memory and made a faster processing for that possibleCard deck (time for vintages and letters was given away time). Here mechanisms were already extensively used, like the Spooling and the possibility of the off-line - enterprise. However a program was necessary that such as I/O administration, store management and above all CCU Scheduling takes care of tasks.Starting from this time one could talk about the beginning of an operating system.

The next steps were then consequences of the respective fields, which came the systems to part. The following systems developed up to the today's day and in the employment: Parallel systems, Distributed systems, personnel computer - systems, time-sharing systems, real-time systems and in most recent time also the so-called Handheld systems.

In the PC - Range are at present the usually-used operating systems the different variants of Microsoft Windows, Apple Mac OS X, Linux (GNU - License), OS/2 and/or. eComstation as well as BSD Unix. For special applications (example: industrielle control) are used also experimental operating systems for research and training purposes.

Apart from the classical variants there are still special operating systems for distributed systems, with those between thatlogical system and the physical system (EN) one differentiates. The logical computer consists of several physical computer units. Many large computers, NUMBER Cruncher and the legendary systems from the house Cray work according to this principle. One of the most well-known operating systems within the range of distributed systems is Amoeba.

See also: List of the operating systems

the tasks of the operating system can be summarized with the following references:

  • Prompting
  • shop and interruption of the devices
  • supply attached by
  • programs administration of the processor time administration
  • of the storage location for uses
  • administration of utility programs (inDifference to application programs)

of programs, management of equipment and memory

to the tasks of an operating system belong usually:

  • Store management
    • assignment and monitoring of the operational funds memory (main and background accumulator).
    • Guidance of tables of the storage allocation by user jobs and/or. Processes (current programs).
    • Operation ofRequirements and release of memory.
  • Program (process) - administration
    • support of all processes (in the expiration of programs present) in the computer system.
    • Production of new processes at the request of the operating system and/or. other existing processes,
    • distance of processes from the system.
    • Communication and synchronisation of processesamong themselves (interprocess communication)
  • devices - and file management
    • efficient assignment of in/output devices and switching units (data channels, control units), avoidance of conflicts
    • initiation, monitoring of the execution, time limitation of in/output procedures.
    • Administration of the file system. Production of a name area with associated memory objects and if necessary further objects.
  • Abstraction
    • hiding the complexity of the machine from the user
    • abstraction of the machine term (after Coy):
      • Material machine = central processing unit + devices (hardware)
      • abstract machine = material machine + operating system
      • user machine = abstract machine + application program

as equipment from the view oneOperating system designates one for historical reasons everything that is addressed via in/output channels. These are not only devices in the conventional sense, but meanwhile also internal extensions such as diagram maps, network maps and other one. „Devices “one designates (under) the programs for the initialization and control of thesein summary as device drivers.

utility programs and application programs

most operating systems contain utility programs, also of utilities or tools (Tools) mentioned. They make possible for the user and/or. Administrator the treatment more generally as well as systemnear tasks. In addition among other things editors belong,Copying programs, user administration programs, system-monitoring device programs and tools for the data protection.

Application programs do not rank usually among the actual operating system. They come either from the manufacturer of the system or from other offerers. Application programs can be delivered also with the operating system (examples: Many programs in Linux- Distributions or the Internet Explorer as part of Microsoft Windows).

operational fund administration and abstraction

as operational funds or resources one designates all components provided of the hardware of a computer, thus the processor (with multiprocessor systems the processors), thatphysical memory and all devices such as non removable disk, disk and CD-ROM drive assemblies, network and interfaces adapters and others. The hardware Compatibility cunning contains all hardware - of products, which were tested in connection with a certain operating system on their functionality.

Einführendes example: Interval timer components

modern trend of computer systems possess interval timer components (timers). In early PCs z became. B. the component 8284 of the company Intel assigned. This component must be first initialized. It can interrupt then at expiration of one time interval or periodically the processor andit to the processing of an own routine cause. Apart from the initialization an interruption routine is to be provided, whose call in a language suitable for it (usually assembler) must be programmed. Since interruptions arise asynchronously, complex conditions are to be considered regarding the data structures.Exact knowledge of the component (data sheet), the computer hardware (interrupt handling) and the processor is necessary. One summarizes the individual components, which are involved in this process, under the term computer architecture.

virtual processors

a modern multiprogramming system uses suchInterval timer component, in order to interrupt the normally only processor periodically (normally within the millisecond range) and possibly continue with another program (preemptive multitasking so mentioned). The initialization and the interruption routine are implemented thereby by the operating system. Even if only an individual processoris available, can several programs be implemented, each program receives a part the processor time (Scheduling). Each program behaves, up to the slowed down run time, as if it would have its own virtual processor.

Virtual interval timers

over a system call, z. B. alarm, is put to each program beyond that its own virtual interval timer at the disposal. The operating system counts the interruptions of the original interval timer and informs programs, which the alarm - system call used. The individual times becomeover a queue administers.


the hardware of the interval timer is hidden thereby from the programs. A system with storage protection permits the access to the interval timer component only over the Kernel and only over accurately defined interfaces (usually system callsto be called, those over special processor instructions such as TRAP, BRK, INT be realized). No program can endanger thus the system, the use of the virtual interval timer is simple and portable. The user or programmer does not need to worry about (complex) the details.

Virtualisierung of further operational funds

as processors and interval timers to be virtualisiert , is possible this also for all other operational funds. Some abstractions are implemented partly only than software, others require special hardware.

file systems

over file systemsthe details of the external memory systems (non removable disk, disk or CD-ROM drive assemblies) are hidden. File names and listings permit the comfortable access, the actually existing block structure and the equipment differences are perfectly invisible.

internal memory

the internal memory (RAM) becomesmade available into blocks (tiles) divided and the appropriate programs. Over virtual memory with many systems a continuous (coherently) range is put to each program at the disposal. This memory is physically not being connected, it can even unused parts on thatexternal memory paged out its. The virtual memory of a program can be even larger than the material memory.


the details of the network accesses are hidden, as on the actual hardware (network map) a minutes pile is put on. The network often commodity permitsas many as desired virtual channels. On the level of the Sockets (programming) the network map is perfectly invisible, the network many new abilities (bi-directional, reliable data streams, addressing, Routing) got.


as graphic user surface (GUI, graphic user interface) becomes generala display output described, if it goes beyond a prompt. With the correct diagram maps and screens the representation of geometrical objects (lines, circles, ellipses, in addition, writing attributes and colors) on the screen possible, from those is itself more complex geometrical elements howButtons, menu, etc.User surfaces for simply steering of programs to provide leave.

The diagram map as hardware is perfectly hidden for the programmer and user.

history and examples of the operational fund administration

first operating systems (until 1980)

Maurice Vincent Wilkes
Maurice VincentWilkes
the first computers did not possess operating systems. This was on the one hand because of their building method (mechanical calculating machines such as Abacus, slide rule etc.) or at its strongly limited operational area (Mark of I, ENIAC, Colossus). With the invention and the employment of the Transistor (1947) and the invention of the microprogramming 1955 by Maurice Wilkes in the consequence no more individual machines, but whole model rows were used. Each manufacturer supplied different operating systems at this time even for different model rows of his products, so thatPrograms only in a certain model row ran and neither between different computer nor over different generations were portierbar.

With the introduction of the model row System/360 of IBM IBM introduced 1964 the operating system OS/360. It was model-line up-spreading the first operating system, thatone used. Starting from 1963 Multics was developed General Electric and the Bell lab in co-operation by ALSO , by AT&T, which were however only starting from 1969 to 2000 in use. Multics was programmed in PL/I. Inspired from the workMultics started a group around Ken Thompson and Dennis Ritchie to the Bell Laboratories of AT&T 1969 with the development of Unix. Unix became in the years 1972 - 1974 up to few parts in the higher programming language Cwith the goal of the portability implements again. At this time also the operating system CP/M was far common.

the C64, a home computer of the 1980er years

into the 1980er years became popular home computers. These could apart from useful tasks alsoPlays implement. The hardware consisted of an 8-bit processor with up to 64KB RAM, a keyboard and a monitor and/or. HF-exit. One the most popular this computer was the Commodore C64 with the microprocessor 6510. This computer had a 8KB-ROM BIOS,that the devices screen, keyboard, serial International Electronical Commission interface for floppy disk drives and/or. Printer, cartridge interface initialized and over a channel concept partly abstracted. Over a 8KB-ROM BASIC, which touched down on the functions of the BIOS, could be served and programmed the system. The operating systemthis computer can be regarded on the level of the BASIC interpreter as good hardware abstraction. Naturally neither Kernel are present, memory or other hardware protection. Many programs, above all also plays, jumped over themselves over the BIOS and seized directly on appropriate hardwaretoo.

Abstraktionsschichten im Betriebssystem des Heimcomputers C64

Abstraction layers in the operating system of the home computer C64

the graphic user surface (GUI) of Apple

Dominik Hagen, a former coworker of Xerox, motivated to visit Steve job, Xerox Palo Alto Research center (PARK).There jobs above all the prototype of a Smalltalk was shown - development system (Xerox developed first computers with graphic user surface with ALTO (1973) and star (1981)). Apple offered Xerox to buy the technology; there PARK however forwardseverything a research center was, existed no interest in sales and marketing. After Steve offered job Xerox stock shares of Apple, Apple developers the Xerox demos were permitted to him unite to show. Afterwards the Apple developers in any case was clear that the graphic user surfacethe future belonged, and Apple began to develop own GUI.

Many characteristics and principles of each modern graphic user surface for computers, how we know them today, are original Apple developments (pull-down menu, the desk metaphor, Drag&Drop, double clicking). The statement,Apple has its GUI von Xerox “abgekupfert” is a constant point at issue; however serious differences between a Alto of Xerox and the Lisa /dem Macintosh exist).

Apple I computer

after separating Steve job from the enterprise setwith Apple the phase of the Pragmatiker. Successor from jobs became former Pepsi adjusted by him - manager John Sculley, it followed 1993 the German Michael Spindler. 1996 were replaced Spindler from Gil Amelio.

The Mac OS successor

in the middle of the 1990er years was Apple in a deep crisis; the company seemed short before the ruin. An urgent problem participated that of Apple was regarded operating system as outdated and Apple after alternatives to look around began. After thatFail the most important project for a modern operating system with the code name to copilot country saw themselves forced Apple to regard for to look out as the own purposes usable successor for the own operating system. First it was assumed that Apple the company Incorporated, with their also on Macs executable operating system BeOS, would take over. The assumption negotiations failed however in November 1996, there the former Apple manager and boss of Jean Louis Gassée in case of an assumption 300 million US Dollar and a seatin the executive committee required. Since Amelio had promised to announce up to the MacWorld in January 1997 the future strategy regarding Mac OS fast an alternative had to be found. Surprisingly Apple then still transferred the company NEXT one in December 1996the Apple founder Steve job and their operating system NEXT step/open step for 400 million US Dollar. This should become the basis for the following generation of the Apple operating system. That the new requirements adapted and optically updated NEXT steps became then under the name Mac OS Xa large success. With the assumption of NEXT one also a new firm culture drew in with Apple. Steve job, into which 1980ern of the company along-created by him vergrault, now Chief Executive Officer (CEO) of NEXT one, became 1997 againHead of the company by Apple.Avie Tevanian, also a NEXT coworker, took over the development department. The Lizenzierung of the operating system terminated jobs to other manufacturers (z. B. Power Computing) and stopped the production Newton . With the introduction of the a riser computer iMac Apple leda new organization of these computers: They were from now on transparency and color glad.Jonathan Ive, the Gestalter iMacs, became a boss of the organization department with Apple.

DOS, a diskette operating system

the origin of DOS lies in CP/M and became 1974 of digitally Research assigned. The Portierung on Motorola 68000, called the CP/M-68k, even no large commercial success, became the basis for TOS, the operating system of the Atari pc. MS-DOS version 1.0 appeared 1981 as reproduction of CP/Mand for PCs one used. It touches down on the BIOS and makes file system operations available.

First IBM - PCs were developed completely similarly as the C64. Also they had an inserted BIOS for the initialization and abstraction thatHardware. Even a BASIC interpreter was present. Contrary to the BIOS BASIC however in the compatible computers of other companies one did without.

The PC could address the first models with its Intel-8088 - processor (16-Bit register) up to 1 MT memory,were equipped however only with 64KB. Floppy disk drives replaced the old Kassettenrekorder as storage medium. They permit multiple writing and reading individually addressable 512-Byte-Blöcke. The use is simplified by a diskette operating system (disk operating system, DOS), which makes an abstract file concept available. Blockscan be combined into of any size Clustern (allocation unit, smallest unit accessible for the operating system). Files (logical information units) occupy or several (concatenated) this cluster. A disk can contain many files, which are attainable over names.

On the first PCs was no storage protection realized, the programs could access therefore at DOS past directly BIOS and even the hardware. Only later PCs were equipped processor , which made storage protection possible with the Intel-80286 -. MS-DOS placed also no degree of abstraction sufficient for all purposesfor the order. Only one program could be at the same time started, the store management was rather rudimentary. A part of the hardware was not supported and had to be addressed by programs directly, which led to the fact that for example for each play the sound map againto be configured had. The performance of some routines, particularly to the text edition, was improvement worthy. Many programs jumped over themselves therefore inevitably over the operating system and wrote z. B. directly into the screen memory. MS-DOS became with a sentence of programs (tools so mentioned)and a command interpreter (COMMAND.COM) delivered.

Abstraktionsschichten eines PC unter DOS

, A modern multi-program system 1991

Linus Torvalds in

Helsinki/Finland began abstraction layers PC under

DOS [ work on] of a Linux (GNU/Linux) with the development of Linux, which he soon thereafter the public for the orderplaced.

Portable operating system runs on different computer architectures, became however first for PCs with Intel 80386 as - processor develops. The BIOS used in these computers serves only for initializing the hardware and for starting the operating system Kernels, therethe routines of the BIOS for multi-program systems such as Linux are unsuitable. This comes off, there in particular the processor by control rooms is loaded instead of by one - in the hardware quite existing - skillful interruption administration (interrupt handling) on events (to react events). Linux uses therefore after starting the system own device drivers.

It distributes the processor time on different programs (processes). Each of these processes receives its own, protected storage area and can only over system calls on the device drivers and thatOperating system access.

The processes run in the user mode (user mode), during which Kernel in the core locate mode (kernel mode) works. The privileges in the user mode are very reduced. Abstraction and storage protection are almost perfect, direct accesses become only muchrarely and under exactly controlled conditions permits. This has the advantage that no program z. B. due to an error the system to the crash to bring can.

Linux places like its model Unix a complete abstraction and Virtualisierung for almost all operational fundsready (z. B.virtual memory, illusion of an own processor etc.).

Abstraktionsschichten unter Linux

Nearly complete abstraction under Linux

Microsoft Windows

1983 began the company Microsoft with the development of a diagramable operating system essay for MS-DOS named Windows - it actedhowever not around an operating system. The MS-DOS and BIOS Design of the PCs did not permit advancement toward modern server operating systems. Microsoft began to develop at the beginning of the 1990er such an operating system, that first as advancement of OS/2 was planned (Microsoft was between1987-1991 at the development take part): Windows NT 3,1 (July 1993). For the Consumer market Microsoft brought to 15. August 1995 Windows 95 out, it is based on MS-DOS. This “Consumer branch” was locked with the publication of Windows Millennium (August/September 2000).

Structureof Windows NT: Over the hardware an abstraction layer was put, to the hardware Abstraction Layer (HAL ), on which the Kernel touched down. Different device drivers were implemented as core modules and ran like the Kernel in the privileged Kernel mode. They placed possibilities to thatI/O administration, file system, network, safety mechanisms, virtual memory etc. for the order. System services (system services) supplemented the concept; like their UNIX - counterparts, daemons, were implemented them in the form of processes in the user mode.

Abstraktionsschichten unter Windows NT

Abstraction layers under Windows NT (something simplified)

overPersonalities so mentioned was then copied the interfaces of existing systems, first for Microsoft own, new Win32-System, in addition, for OS/2 (without diagram) and POSIX,1, thus from a standard, which actually Unix - systems to standardize should. Personalities ran like user programs in the unprivilegierten User mode. The DOS subsystem was implemented in the form of processes, which in each case represented a complete PC with MS-DOS as virtual machine; whereupon could with a special version of Windows 3,1, which Windows on Windows, also Win16-Programme are implemented. Windows on Windows dazzled in additionthe windows of the Win16-Programme into the Win32-Subsystem, which administered the expenditure for diagram. The system permitted therefore the execution of programs both for MS-DOS and for the older Windows operating systems, however under perfect control of the operating system. This applied however only to thoseImplementation for Intel-80386-Prozessoren and their successor.

Programs, which access directly the hardware, remained however outside forwards. In particular many plays could not be implemented therefore under Windows NT, at least up to the conception of WinG, which was renamed later in DirectX.Without the possibility of a direct access to the diagram hardware and/or. - driver was first limited to the older Windows versions the programming of efficient Actionspielen.

Windows NT appeared in the versions 3,1, 3,5, 3,51 and 4.0. Windows 2000 placed an advancement ofWindows NT. Also Windows XP, Windows server 2003 and Windows Vista develop on the structure of Windows NT .

see also

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