Kernal of Oparating System
The central module of an operating system. It is the part of the operating system that loads first, and it remains in main memory. Because it stays in memory, it is important for the kernel to be as small as possible while still providing all the essential services required by other parts of the operating system and applications. Typically, the kernel is responsible for memory management, process and task management, and disk management.
The central module of an operating system. It is the part of the operating system that loads first, and it remains in main memory. Because it stays in memory, it is important for the kernel to be as small as possible while still providing all the essential services required by other parts of the operating system and applications. Typically, the kernel is responsible for memory management, process and task management, and disk management.
In computing, the kernel is the central component of most computer operating systems; it is a bridge between applications and the actual data processing done at the hardware level. The kernel's responsibilities include managing the system's resources (the communication between hardware and software components).[1] Usually as a basic component of an operating system, a kernel can provide the lowest-level abstraction layer for the resources (especially processors and I/O devices) that application software must control to perform its function. It typically makes these facilities available to application processes through inter-process communication mechanisms and system calls.
Operating system tasks are done differently by different kernels, depending on their design and implementation. While monolithic kernels execute all the operating system code in the same address space to increase the performance of the system, microkernels run most of the operating system services in user space as servers, aiming to improve maintainability and modularity of the operating system.[2] A range of possibilities exists between these two extremes.
Operating system tasks are done differently by different kernels, depending on their design and implementation. While monolithic kernels execute all the operating system code in the same address space to increase the performance of the system, microkernels run most of the operating system services in user space as servers, aiming to improve maintainability and modularity of the operating system.[2] A range of possibilities exists between these two extremes.
On the definition of "kernel", Jochen Liedtke said that the word is "traditionally used to denote the part of the operating system that is mandatory and common to all other software."[3] Most operating systems rely on this concept of the kernel. The existence of a kernel is a natural consequence of designing a computer system as a series of abstraction layers,[4] each relying on the functions of layers beneath it. The kernel, from this viewpoint, is simply the name given to the lowest level of abstraction that is implemented in software. In order to avoid having a kernel, one would have to design all the software on the system not to use abstraction layers; this would increase the complexity of the design to such a point that only the simplest systems could feasibly be implemented.
While it is today mostly called the kernel, originally the same part of the operating system was also called the nucleus or core[1][5][6][7], and was originally conceived as containing only the essential support features of the operating system. However the term core has also been used to refer to the primary memory of a computer system, because some early computers used a form of memory called core memory.
In most cases, the boot loader starts executing the kernel in supervisor mode.[8] The kernel then initializes itself and starts the first process. After this, the kernel does not typically execute directly, only in response to external events (e.g., via system calls used by applications to request services from the kernel, or via interrupts used by the hardware to notify the kernel of events). Additionally, the kernel typically provides a loop that is executed whenever no processes are available to run; this is often called the idle process.
Kernel development is considered one of the most complex and difficult tasks in programming.[9] Its central position in an operating system implies the necessity for good performance, which defines the kernel as a critical piece of software and makes its correct design and implementation difficult. For various reasons, a kernel might not even be able to use the abstraction mechanisms it provides to other software. Such reasons include memory management concerns (for example, a user-mode function might rely on memory being subject to demand paging, but as the kernel itself provides that facility it cannot use it, because then it might not remain in memory to provide that facility) and lack of reentrancy, thus making its development even more difficult for software engineers.
A kernel will usually provide features for low-level scheduling[10] of processes (dispatching), inter-process communication, process synchronization, context switching, manipulation of process control blocks, interrupt handling, process creation and destruction, and process suspension and resumption (see process states).
While it is today mostly called the kernel, originally the same part of the operating system was also called the nucleus or core[1][5][6][7], and was originally conceived as containing only the essential support features of the operating system. However the term core has also been used to refer to the primary memory of a computer system, because some early computers used a form of memory called core memory.
In most cases, the boot loader starts executing the kernel in supervisor mode.[8] The kernel then initializes itself and starts the first process. After this, the kernel does not typically execute directly, only in response to external events (e.g., via system calls used by applications to request services from the kernel, or via interrupts used by the hardware to notify the kernel of events). Additionally, the kernel typically provides a loop that is executed whenever no processes are available to run; this is often called the idle process.
Kernel development is considered one of the most complex and difficult tasks in programming.[9] Its central position in an operating system implies the necessity for good performance, which defines the kernel as a critical piece of software and makes its correct design and implementation difficult. For various reasons, a kernel might not even be able to use the abstraction mechanisms it provides to other software. Such reasons include memory management concerns (for example, a user-mode function might rely on memory being subject to demand paging, but as the kernel itself provides that facility it cannot use it, because then it might not remain in memory to provide that facility) and lack of reentrancy, thus making its development even more difficult for software engineers.
A kernel will usually provide features for low-level scheduling[10] of processes (dispatching), inter-process communication, process synchronization, context switching, manipulation of process control blocks, interrupt handling, process creation and destruction, and process suspension and resumption (see process states).
