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 Assignment I 

1. What is the kernel in an operating system?

The kernel is the essential center of a computer operating system the core that provides basic services forall other parts of the operating system.

A kernel is designed to be a central core to the operating system - the logic that manages the resources thatthe hardware has to offer.

The kernel is the central part of an operating system, that directly controls the computer hardware. Usually,the kernel is the first of the user-installed software on a computer, booting directly after the BIOS. Operating system kernels are specific to the hardware on which they are running, thus most operating

systems are distributed with different kernel options that are configured when the system is installed.Changing major hardware components such as the motherboard, processor, or memory, often requires akernel update. Additionally, often new kernels are offered that improve system security or performance. Thetwo major types of kernels competing in today's computer markets are the Windows kernel and the unix-likekernels.

The Windows kernel is available only with the Microsoft Windows series of operating systems. It isproprietary software, developed and distributed by Microsoft Corporation. Introduced in Windows/386, it'smany incarnations have since gone by several different names, and some had no names at all. The latest

version of the Windows kernel was introduced in Windows NT, and has had many of it's functions removedand placed in user-mode software for Windows Vista. This leads to increased system stability and security.In Vista, application-level software exploits have much less access to the core functions of the operatingsystem, and application crashes will not bring down the OS.

The Kernel is the central component of most computer operating systems (OS).Its responsibilities include managing the system's resources (the communicationbetween hardware and software components)A kernel can be contrasted with a shell (such as bash, csh or ksh in Unix-like operating systems), which is the outermost part of an operating system and aprogram that interacts with user commands. The kernel itself does not interactdirectly with the user, but rather interacts with the shell and other programs as

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well as with the hardware devices on the system, including the processor (alsocalled the central processing unit or CPU), memory and disk drives.The kernel is the first part of the operating system to load into memory duringbooting (i.e., system startup), and it remains there for the entire duration of thecomputer session because its services are required continuously. Thus it is

important for it to be as small as possible while still providing all the essentialservices needed by the other parts of the operating system and by the variousapplication programs.

2. Briefly explain the difference between a tightly couple system and aloosely coupled system.

Loosely coupled microprocessors are more like independent processors joined via a small communicationlink (a high speed bus or cable). This means that the connected microprocessors have their own localmemory sets. They are low in performance. Also only microprocessors that can work independently may beused.

Tightly coupled microprocessors share a common memory for the purpose of communication. One processor

(slave) is dependent on the other (master). They are good at performance. The connected processors alsohave local memory sets for general purposes.

One feature that is commonly characterizing tightly coupled systems is that theyshare the clock.Therefore multiprocessors are typically tightly coupled but distributedworkstations on a network are not.Another difference is that: in a tightly-coupled system, the delay experiencedwhen a message is sent from one computer to another is short, and data rate ishigh; that is, the number of bits per second that can be transferred is large. In aloosely-coupled system, the opposite is true: the intermachine message delay islarge and the data rate is low. For example, two CPU chips on the same printedcircuit board and connected by wires etched onto the board are likely to be

tightly coupled, whereas two computers connected by a 2400 bit/sec modemover the telephone system are certain to be loosely coupled.

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3. Briefly explain the different states of a process by using a suitable

diagram.

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The following typical process states are possible on computer systems of all kinds. In

most of these states, processes are "stored" on main memory.

Created(Also called new.) When a process is first created, it occupies the "created" or "new"state. In this state, the process awaits admission to the "ready" state. This admission willbe approved or delayed by a long-term, or admission, scheduler. Typically in mostdesktop computer systems, this admission will be approved automatically, however forreal time operating systems this admission may be delayed. In a real time system,admitting too many processes to the "ready" state may lead to over saturation and over

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contention for the systems resources, leading to an inability to meet process deadlines.Process means the program that is currently running, or that part of program currentlyused by processor.

Ready(Also called waiting' or runnable.) A "ready" or "waiting" process has been loaded into

main memory and is awaiting execution on a CPU (to be context switched onto the CPUby the dispatcher, or short-term scheduler). There may be many "ready" processes atany one point of the systems execution - for example, in a one processor system, onlyone process can be executing at any one time, and all other "concurrently executing"processes will be waiting for execution.

Running(Also called active or executing.) A "running", "executing" or "active" process is a processwhich is currently executing on a CPU. From this state the process may exceed itsallocated time slice and be context switched out and back to "ready" by the operatingsystem, it may indicate that it has finished and be terminated or it may block on someneeded resource (such as an input / output resource) and be moved to a "blocked" state.

Blocked(Also called sleeping.) Should a process "block" on a resource (such as a file, asemaphore or a device), it will be removed from the CPU (as a blocked process cannotcontinue execution) and will be in the blocked state. The process will remain "blocked"until its resource becomes available, which can unfortunately lead to deadlock. Fromthe blocked state, the operating system may notify the process of the availability of theresource it is blocking on (the operating system itself may be alerted to the resourceavailability by an interrupt). Once the operating system is aware that a process is nolonger blocking, the process is again "ready" and can from there be dispatched to its"running" state, and from there the process may make use of its newly availableresource.

TerminatedA process may be terminated, either from the "running" state by completing itsexecution or by explicitly being killed. In either of these cases, the process moves to the"terminated" state. If a process is not removed from memory after entering this state,this state may also be called zombie