Operating System

Operating system ( operating system; OS) is a set of programs that manage computer hardware resources, and provide common services for application software. The operating system is the most important types of system software in the computer system. Without an operating system, users can not run application programs on their computers, except for self-booting application programs.

Time-sharing operating system schedules tasks for efficient use of the system and may also include accounting for cost allocation of processor time, mass storage, printing, and other resources.

For the hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between application programs and computer hardware,  although the application code is usually executed directly by the hardware and OS frequently will contact or disconnected by it. The operating system is found on nearly all devices that contain computer-from cell phones and video game consoles to supercomputers and web servers.

Examples of popular modern operating systems including Linux, Android, IOS, Mac OS X, and Microsoft Windows. 

Usually, the term Operating System often addressed to all the software included in a package with the computer system before the software applications installed. The operating system is a software system whose job is to perform control and management of hardware and basic system operations, including running software applications such as word processing programs and a web browser.

In general, the Operating System is software on the first layer is placed on computer memory when the computer starts up. While other software is run after running the Operating System and Operating System will perform the core public service for the software. Common core services such as access to the disk, memory management, task scheduling, and user interface. So that each software no longer need to perform the core duties of the public, because it can be served and performed by the operating system. Section of code that perform the core duties and the general is called the "kernel" an Operating System

If the computer system is divided into layers, then the Operating System is the link between the hardware layer and software layer. Beyond that, Operating Systems perform all important tasks in the computer, and ensure that different applications can be running simultaneously with the smooth. Operating System ensures other software applications can use the memory, perform input and output to other equipment, and have access to the file system. If multiple applications running simultaneously, then the Operating System right set schedule, so far as possible all running processes have enough time to use the processor (CPU) and do not interfere with each other.

In many cases, the Operating System provides a library of standard functions, which other applications can call functions, so that in each new program, no need to create these functions from scratch.

Operating systems generally consist of several parts:

Boot mechanism, namely putting the kernel into memory

Kernel, which is the core of an Operating System

Command interpreter or shell, which reads input from the user

Libraries, which provides a collection of basic functions and standards that can be invoked by other applications

Drivers to interact with external hardware, as well as to control them.

Some operating systems allow only one application running at a time (eg DOS), but most of the new operating system allows multiple applications to run simultaneously at the same time. Operating systems are referred to as Multi-tasking Operating System (eg UNIX family of operating systems). Some operating systems are very large and complex, as well as the input depending on user input, while the other Operating Systems are very small and made with the assumption that work without human intervention at all. The first type is often referred to as a Desktop OS, while the second type is the Real-Time OS, for example is Windows, Linux, Free BSD, Solaris, Palm, Symbian, and so on.

- the current operating system

Operating system-the primary operating system commonly usedcomputer systems (including PCs, personal computer) is dividedinto 3 major groups:

Family of Microsoft Windows - which is comprised of the Windows Desktop Environment (version 1.x to version 3.x),Windows 9x (Windows 95, 98, and Windows ME), and WindowsNT (Windows NT 3.x, Windows NT 4.0 , Windows 2000,Windows XP, Windows Server 2003, Windows Vista, WindowsServer 2008, Windows 7 (Seven), which was released in 2009,and Windows 8 will be released in 2012 or later)).

Unix family of operating systems that use the POSIX interface,such as SCO UNIX, family BSD (Berkeley Software Distribution),GNU / Linux, MacOS / X (based on a modified BSD kernel, and known by the name of Darwin) and GNU / Hurd.

Mac OS, is a computer operating system to output the so-calledApple Mac or Macintosh. The latest operating system is Mac OSX version 10.6 (Snow Leopard). Summer of 2011 planned launch of version 7.10 (Lion).

While mainframe computers, and super computers using manydifferent operating systems vary, generally a derivative of the UNIX operating system developed by vendors such as IBM AIX,HP / UX, etc..

- Proses

The processor executes the computer programs. The processor is a chip in a computer system that runs the computer program instructions. In every second the processor can execute millions of instructions.

The program is a series of instructions given to a computer. While the process is a part of the program residing on a certain status in a series of execution. In the discussion Operating Systems, we are more often discussed the process in comparison with the program. In modern operating systems, at one time not all programs loaded in memory, but only one part of the program. While other parts of the program remains rest in disk storage media. Only in times of need alone, part of the program is loaded in memory and executed by the processor. This is to save memory consumption.

Some systems run only one single process at a time, while others run multi-process at a time. Though most of the computer system has only one processor, and a processor can only execute one instruction at a time. So how a single processor system can run multi-process? Surely, in a very small granularity, the processor executes only one process at a time, then quickly he moved to run other processes, and so on. So for the vision and feeling of a human user, as if the processor to run multiple processes simultaneously.

Each process in an operating system to get a PCB (Process Control Block), which contains information about the process, namely: an identification process (Process ID) a unique identity and become the number, the status of the process, the priority of the process execution and location information in memory processes . Priority process is a value or quantity that indicates how often the process should be executed by the processor. The process that has a higher priority, will be run more often or executed earlier than the lower-priority processes. An operating system can only determine all processes with the same priority, so that each process has the same opportunity. An operating system can also change the priority of a particular process, so that the process will be able to have a greater chance at the next execution (for example: the process that was already too long waiting for execution, the operating system to raise the value priorities).

Mainframes

See also: History of IBM mainframe operating systems

Through the 1950s, many major features were pioneered in the field of operating systems, including batch processing, input/output interrupt, buffering, multitasking, spooling, runtime libraries, link-loading, and programs for sorting records in files. These features were included or not included in application software at the option of application programmers, rather than in a separate operating system used by all applications. In 1959 the SHARE Operating System was released as an integrated utility for the IBM 704, and later in the 709 and 7090 mainframes, although it was quickly supplanted by IBSYS/IBJOB on the 709, 7090 and 7094.

During the 1960s, IBM's OS/360 introduced the concept of a single OS spanning an entire product line, which was crucial for the success of the System/360 machines. IBM's current mainframe operating systems are distant descendants of this original system and applications written for OS/360 can still be run on modern machines.

OS/360 also pioneered the concept that the operating system keeps track of all of the system resources that are used, including program and data space allocation in main memory and file space in secondary storage, and file locking during update. When the process is terminated for any reason, all of these resources are re-claimed by the operating system.

The alternative CP-67 system for the S/360-67 started a whole line of IBM operating systems focused on the concept of virtual machines. Other operating systems used on IBM S/360 series mainframes included systems developed by IBM: COS/360 (Compatabililty Operating System), DOS/360 (Disk Operating System), TSS/360 (Time Sharing System), TOS/360 (Tape Operating System), BOS/360 (Basic Operating System), and ACP (Airline Control Program), as well as a few non-IBM systems: MTS (Michigan Terminal System), MUSIC (Multi-User System for Interactive Computing), and ORVYL (Stanford Timesharing System).

Control Data Corporation developed the SCOPE operating system in the 1960s, for batch processing. In cooperation with the University of Minnesota, the Kronos and later the NOS operating systems were developed during the 1970s, which supported simultaneous batch and timesharing use. Like many commercial timesharing systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the PLATO operating system, which used plasma panel displays and long-distance time sharing networks. Plato was remarkably innovative for its time, featuring real-time chat, and multi-user graphical games. Burroughs Corporation introduced the B5000 in 1961 with theMCP, (Master Control Program) operating system. The B5000 was a stack machine designed to exclusively support high-level languages with no machine language or assembler, and indeed the MCP was the first OS to be written exclusively in a high-level language – ESPOL, a dialect of ALGOL. MCP also introduced many other ground-breaking innovations, such as being the first commercial implementation of virtual memory. During development of the AS400, IBM made an approach to Burroughs to licence MCP to run on the AS400 hardware. This proposal was declined by Burroughs management to protect its existing hardware production. MCP is still in use today in the UnisysClearPath/MCP line of computers.

UNIVAC, the first commercial computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this was a batch-oriented system that managed magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time Basic (RTB) system to support large-scale time sharing, also patterned after the Dartmouth BC system.

General Electric and MIT developed General Electric Comprehensive Operating Supervisor (GECOS), which introduced the concept of ringed security privilege levels. After acquisition by Honeywell it was renamed to General Comprehensive Operating System (GCOS).

Digital Equipment Corporation developed many operating systems for its various computer lines, including TOPS-10 and TOPS-20 time sharing systems for the 36-bit PDP-10 class systems. Prior to the widespread use of UNIX, TOPS-10 was a particularly popular system in universities, and in the early ARPANET community.

In the late 1960s through the late 1970s, several hardware capabilities evolved that allowed similar or ported software to run on more than one system. Early systems had utilized microprogramming to implement features on their systems in order to permit different underlying architecture to appear to be the same as others in a series. In fact most 360s after the 360/40 (except the 360/165 and 360/168) were microprogrammed implementations. But soon other means of achieving application compatibility were proven to be more significant.

The enormous investment in software for these systems made since 1960s caused most of the original computer manufacturers to continue to develop compatible operating systems along with the hardware. The notable supported mainframe operating systems include:

Burroughs MCP – B5000, 1961 to Unisys Clearpath/MCP, present.

IBM OS/360 – IBM System/360, 1966 to IBM z/OS, present.

IBM CP-67 – IBM System/360, 1967 to IBM z/VM, present.

UNIVAC EXEC 8 – UNIVAC 1108, 1967, to OS 2200 Unisys Clearpath Dorado, present.

Unix and Unix-like operating systems

Ken Thompson wrote B, mainly based on BCPL, which he used to write Unix, based on his experience in the MULTICS project. B was replaced by C, and Unix developed into a large, complex family of inter-related operating systems which have been influential in every modern operating system (see History).Main article: Unix

The Unix-like family is a diverse group of operating systems, with several major sub-categories including System V, BSD, and GNU/Linux. The name "UNIX" is a trademark ofThe Open Group which licenses it for use with any operating system that has been shown to conform to their definitions. "Unix-like" is commonly used to refer to the large set of operating systems which resemble the original Unix.

Unix-like systems run on a wide variety of machine architectures. They are used heavily forservers in business, as well as workstations in academic and engineering environments. Free Unix variants, such as GNU/Linux and BSD, are popular in these areas.

Four operating systems are certified by the The Open Group (holder of the Unix trademark) as Unix. HP's HP-UX and IBM's AIX are both descendants of the original System V Unix and are designed to run only on their respective vendor's hardware. In contrast, Sun Microsystems's Solaris Operating System can run on multiple types of hardware, including x86 and Sparc servers, and PCs. Apple's Mac OS X, a replacement for Apple's earlier (non-Unix) Mac OS, is a hybrid kernel-based BSD variant derived from NeXTSTEP, Mach, andFreeBSD.

Unix interoperability was sought by establishing the POSIX standard. The POSIX standard can be applied to any operating system, although it was originally created for various Unix variants

BSD and its descendants

Main article: Berkeley Software Distribution

A subgroup of the Unix family is the Berkeley Software Distribution family, which includesFreeBSD, NetBSD, and OpenBSD. These operating systems are most commonly found onwebservers, although they can also function as a personal computer OS. The Internet owes much of its existence to BSD, as many of the protocols now commonly used by computers to connect, send and receive data over a network were widely implemented and refined in BSD. The world wide web was also first demonstrated on a number of computers running an OS based on BSD called NextStep.

BSD has its roots in Unix. In 1974, University of California, Berkeley installed its first Unix system. Over time, students and staff in the computer science department there began adding new programs to make things easier, such as text editors. When Berkely received new VAX computers in 1978 with Unix installed, the school's undergraduates modified Unix even more in order to take advantage of the computer's hardware possibilities. The Defense Advanced Research Projects Agency of the US Department of Defense took interest, and decided to fund the project. Many schools, corporations, and government organizations took notice and started to use Berkeley's version of Unix instead of the official one distributed by AT&T.

Steve Jobs, upon leaving Apple Inc. in 1985, formed NeXT Inc., a company that manufactured high-end computers running on a variation of BSD called NeXTSTEP. One of these computers was used by Tim Berners-Lee as the first webserver to create the World Wide Web.

Developers like Keith Bostic encouraged the project to replace any non-free code that originated with Bell Labs. Once this was done, however, AT&T sued. Eventually, after two years of legal disputes, the BSD project came out ahead and spawned a number of free derivatives, such as FreeBSD and NetBSD

Mac OS X

The standard user interface of Mac OS X

Main article: Mac OS X

Mac OS X is a line of open core graphical operating systems developed, marketed, and sold by Apple Inc., the latest of which is pre-loaded on all currently shipping Macintoshcomputers. Mac OS X is the successor to the original Mac OS, which had been Apple's primary operating system since 1984. Unlike its predecessor, Mac OS X is a UNIX operating system built on technology that had been developed at NeXT through the second half of the 1980s and up until Apple purchased the company in early 1997.

The operating system was first released in 1999 as Mac OS X Server 1.0, with a desktop-oriented version (Mac OS X v10.0) following in March 2001. Since then, six more distinct "client" and "server" editions of Mac OS X have been released, the most recent being Mac OS X 10.7, which was first made available on July 20, 2011. Releases of Mac OS X are named after big cats; the current version of Mac OS X is "Lion".

The server edition, Mac OS X Server, is architecturally identical to its desktop counterpart but usually runs on Apple's line of Macintosh serverhardware. Mac OS X Server includes work group management and administration software tools that provide simplified access to key network services, including a mail transfer agent, a Samba server, an LDAP server, a domain name server, and others. In Mac OS X v10.7 Lion, all server aspects of Mac OS X Server have been integrated into the client version.

Plan 9

Ken Thompson, Dennis Ritchie and Douglas McIlroy at Bell Labs designed and developed the C programming language to build the operating system Unix. Programmers at Bell Labs went on to develop Plan 9 and Inferno, which were engineered for modern distributed environments. Plan 9 was designed from the start to be a networked operating system, and had graphics built-in, unlike Unix, which added these features to the design later. It is currently released under the Lucent Public License. Inferno was sold to Vita Nuova Holdings and has been released under a GPL/MIT license.created for various Unix variants.

Linux and GNU

Main articles: GNU, Linux, and Linux kernel

Ubuntu, a Unity desktop Linux distribution

Linux (or GNU/Linux) is a Unix-like operating system that was developed without any actual Unix code, unlike BSD and its variants. Linux can be used on a wide range of devices from supercomputers to wristwatches. The Linux kernel is released under an open source license, so anyone can read and modify its code. It has been modified to run on a large variety of electronics. Although estimates suggest that Linux is used on 1.82% of all personal computers, it has been widely adopted for use in servers and embedded systems(such as cell phones). Linux has superseded Unix in most places, and is used on the 10 most powerful supercomputers in the world. The Linux kernel is used in some popular distributions, such as Red Hat, Debian, Ubuntu, Linux Mint and Google's Android.

The GNU project is a mass collaboration of programmers who seek to create a completely free and open operating system that was similar to Unix but with completely original code. It was started in 1983 by Richard Stallman, and is responsible for many of the parts of most Linux variants. For this reason, some claim that the combined product of the Linux kernel and the GNU software collection is more correctly called GNU/Linux. Thousands of pieces of software for virtually every operating system are licensed under the GNU General Public License. Meanwhile, the Linux kernel began as a side project of Linus Torvalds, a university student from Finland. In 1991, Torvalds began work on it, and posted information about his project on a newsgroup for computer students and programmers. He received a wave of support and volunteers who ended up creating a full-fledged kernel. Programmers from GNU took notice, and members of both projects worked to integrate the finished GNU parts with the Linux kernel in order to create a full-fledged operating system.

Google Chrome OS

Main article: Google Chrome OS

Chrome is an operating system based on the Linux kernel and designed by Google. Since Chrome OS targets computer users who spend most of their time on the Internet, it is mainly a web browser with no ability to run applications. It relies on Internet applications (or Web apps) used in the web browser to accomplish tasks such as word processing and media viewing, as well as online storage for storing most files

AmigaOS

Main article: AmigaOS

AmigaOS is the default native operating system of the Amiga personal computer. It was developed first by the Amiga Corporation then sold toCommodore International, and initially introduced in 1985 with the Amiga 1000. Early versions (1.0-3.9) run on the Motorola 68k series of 16-bit and 32-bit microprocessors, while the newer AmigaOS 4 runs only on PowerPC microprocessors. On top of a preemptive multitasking kernel called Exec, it includes an abstraction of the Amiga's unique hardware, a disk operating system called AmigaDOS, a windowing system API called Intuition and a graphical user interface called Workbench. A command line interface called AmigaShell is also available and integrated into the system. The GUI and the CLI complement each other and share the same privileges. The current holder of the Amiga intellectual properties is Amiga Inc. They oversaw the development of AmigaOS 4 but did not develop it themselves, contracting it instead to Hyperion Entertainment. On 20 December 2006, Amiga Inc terminated Hyperion's license to continue development of AmigaOS 4. However, in 30 September 2009, Hyperion was granted an exclusive, perpetual, worldwide right to AmigaOS 3.1 in order to use, develop, modify, commercialize, distribute and market AmigaOS 4.x and subsequent versions of AmigaOS (including AmigaOS 5).

Main article: Microsoft Windows

Microsoft Windows originated in 1985 as an application running on top of MS-DOS, which was the standard operating system shipped on most Intel architecture personal computers at the time. In 1995, Windows 95 was released, combining MS-DOS 7.0 with Windows on the same medium, removing the need of getting a separate MS-DOS license. Keeping much legacy, it could run real-mode MS-DOS and 16 bits Windows 3.x drivers. Windows Me, released in 2000, was the latest version of Windows of the Windows 95 family. Later versions have all been based on the Windows NT kernel. Current versions of Windows run on IA-32 and x86-64 microprocessors, although Windows 8 will support ARM architecture. In the past, Windows NT supported a few non-Intel architectures.Microsoft Windows is a family of proprietary operating systems designed by Microsoft Corporationand primarily targeted to Intel architecture based computers, with an estimated 88.9 percent total usage share on Web connected computers.] The newest version is Windows 7 for workstations and Windows Server 2008 R2 for servers. Windows 7 recently overtook Windows XP as most used OS.

Server editions of Windows are widely used. In recent years, Microsoft has expended significant capital in an effort to promote the use of Windows as a server operating environment. However, Windows' usage on servers is not as widespread as on personal computers, as Windows competes against Linux and BSD for server market share.

Older operating systems which are still used in niche markets include OS/2 from IBM and Microsoft; Mac OS, the non-Unix precursor to Apple's Mac OS X; BeOS; XTS-300. Some, most notably Haiku, RISC OS, MorphOS and FreeMint continue to be developed as minority platforms for enthusiast communities and specialist applications. OpenVMS formerly from DEC, is still under active development by Hewlett-Packard. Yet other operating systems are used almost exclusively in academia, for operating systems education or to do research on operating system concepts. A typical example of a system that fulfills both roles is MINIX, while for example Singularity is used purely for research.

Source : Wikipedia