kernel explained- the difference between programs , process, threads and lightweight process смотреть онлайн

Points covered.
1. program
2. process, Intro light wight process
3. thread
4. Difference between them
5. How is the program divided into more than one process?
6. Kernel thread, user thread
7. Usage of both
Introduction
Have you ever wondered what happens when you turn your computer on? How it works? How some physical parts offer us many services while we are sitting in our home? How these components communicate? So, Let me now introduce the world of zeros and ones the world of computers to you by answering these questions.
Kernel
For a computer to start it needs to have an initial simple program to run bootloader, it is stored within the computer hardware in firmware (BIOS). It initializes all aspects of the system. It must locate the operating-system kernel and load it into memory. Then, the system is fully booted. The one program running at all times on the computer is the kernel, it is part of the operating system Everything else is either A system services – system utility or An application program. A system cannot function without the Operating System, and an Operating System cannot exist without the Kernel. Kernel is the operating system core. It functions at the lowest level of the operating system. It is a program which is close to the hardware of the system and so, it performs all the tasks of the operating systems which involve a link between both the hardware and the user level applications operates has a dual mode; systems frequently switch between them. They are Kernel Mode and User Mode. When the computer is running application software, it is in user mode. It is also known as less privileged mode or restricted mode. After the application software request for hardware, the computer enters kernel mode. Kernel mode is also called as system mode. If a process in kernel mode fails, the entire operating system might fail. A kernel thread is the entity handled by the system scheduler. A kernel thread runs within a process but can be referenced by any other thread in the system. The programmer has no direct control over these threads, unless you are writing kernel extensions or device drivers. A user thread is an entity used by programmers to handle multiple flows of controls within a program. The API for handling user threads is provided by the thread’s library. A user thread only exists within a process; a user thread in process A cannot reference a user thread in process B.
Process & programs Thread & light wight process


Process means any program is in execution process when an executable file is loaded into memory. Program is passive entity stored on disk (executable file). One program can be several processes such as java virtual machine.
Process control block controls the operation of any process. Process control block contains information about processes for example Process priority, process id, process state, CPU, register, etc.
A process can creates other processes which are known as Child Processes.
Process takes more time to terminate, and it is isolated means it does not share memory with any other process.
The process can have the following states like new, ready, running, waiting, terminated, suspended. Only one process can be running on any processor core at any instant.
Many processes may be ready and waiting.
The user may be able to run several programs at one time such as a word processor, a web browser, and an e-mail package.
And here is the rule of operating systems to control the flow of process and these called process management.

Thread is the segment of a process means a process can have multiple threads and these multiple threads are contained within a process.
A thread has 3 states: running, ready, and blocked.
Thread takes less time to terminate as compared to process and like process threads do not isolate.
Process means a program is in execution, whereas thread means a segment of a process.
A Process is not Lightweight, whereas Threads are Lightweight process.
They have their own thread ID, a program counter (PC), a register set, and stack but, they share with other threads in the same process code, data, heap sections, and other OS resources, such as open files, permissions, etc.
A Process takes more time to terminate, and the thread takes less time to terminate. Because threads share the same address space, which is an advantage.
The disadvantage is that a problem with one thread in a process will certainly affect other threads and the viability of the process itself.
Now let me wrap this section, Process means a program is in execution, whereas thread means a segment of a process.
A Process is not Lightweight, whereas Threads are Lightweight. A Process takes more time to terminate, and the thread takes less time to terminate.
Thank you for your time.