Usually, the term operating system is often addressed to all software included in a package with computer systems before the software applications installed. The operating system is a software system that served to make the control and management of hardware and basic system operations, including the execution of software applications such as word processing programs and web browsers.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 the operating system is running, and the 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 have a common core tasks, as can be serviced and performed by the operating system. Section of code that performs the core tasks and the general was named to the "kernel" an Operating SystemIf the computer system is divided into layers, then the Operating System is the liaison between the layers of hardware and software layers. Beyond that, the Operating System do all the important tasks in the computer, and ensure that different applications can run simultaneously with the smooth. Operating system software ensures other applications can use the memory, input and output to other equipment, and have access to the file system. If multiple applications running simultaneously, then the operating system to set the exact 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, 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, the core of an Operating System
Command interpreter or shell, which reads input from the user
Libraries, which provide a standard set of basic functions and can be invoked by other applications
Drivers to interact with external hardware, as well as to control them.
Most of the Operating System only allows one application running at the same 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 (such as UNIX family of operating systems). Some operating systems are very large and complex, and its inputs depending on the user input, while other operating systems is 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 a Real-Time OS, for example, is Windows, Linux, Free BSD, Solaris, Palm, Symbian, and so forth.Common core servicesAlong with the development of operating systems, more and more services become a core public service. Now, the OS may need to provide network services and internet connectivity, which was not a core public service. Operating systems also need to keep the damage from the disruption of computer systems from malicious programs that another computer, such as viruses. List of common core services will continue to grow.Programs communicate with each other with the Application Programming Interface, Application Programming Interface or API for short. With this API application program can communicate with the Operating System. As humans communicate with computers through user interface, the program also communicate with other programs via the API.However a computer is not powerful API entirely on the programs that run on the operating platform. For example, if a program created for Windows 3.1 when running on Windows 95 and later generations will see a striking difference between the window program with other programs.Operating systems currentlyOperating system-the primary operating system commonly used computer systems (including PC, personal computer) is divided into 3 major groups:
Family of Microsoft Windows - which is comprised of Windows Desktop Environment (version 1.x to version 3.x), Windows 9x (Windows 95, 98, and Windows ME), and Windows NT (Windows NT 3.x, Windows NT 4.0 , Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows Server 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 is known by the name of Darwin) and GNU / Hurd.
Mac OS, the operating system for Apple computers output is commonly called Mac or Macintosh. The latest operating system is Mac OS X version 10.6 (Snow Leopard). Summer of 2011 planned launch of version 7.10 (Lion).
While the mainframe computer and Super computer operating systems use a lot of different, usually a derivative of the UNIX operating system developed by vendors such as IBM AIX, HP / UX, etc..ProcessThe 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 particular status in a series of execution. In the discussion Operating Systems, we are more likely to discuss the process compared to the program. On 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. It is greatly 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 that the vision and feeling of the 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) and a unique identification number, the status of the process, the priority of the process execution and location information in the memory process . Priority process is a value or quantity that indicates how often the process should be executed by the processor. 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, that process will be able to have a greater chance at the next execution (for example: the process that was already too long to wait for execution, the operating system to raise the priority).Process StatusType of status that may be attributed to a process on any operating system may vary. But at least there are three kinds of status are common, namely:
Ready, namely the status of where the process is ready to be executed on the next turn
Running, which is where the current status of this process is being executed by the processor
Blocked, the status in which the process can not run the processor at the ready / free
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