back the variety of services and also value-added features noted by a modern operating mechanism is continually growing, there room four basic operating mechanism management attributes that are imposed by all operation systems. Every of this management functions is summary described below in bespeak to carry out an as whole context because that what follows. The 4 main operating mechanism management attributes (each of which will be dealt with in better depth elsewhere) are:

process management storage management record and disk monitoring I/O system administration

procedure management

The term process refers here to regimen code that has actually been loaded into a computer"s memory so the it have the right to be executed by the central handling unit (CPU). In a multiprogramming system, there will be a variety of competing processes. The operating mechanism must ensure the each process gets a fair share that the CPU"s time.

before a program deserve to be executed, in ~ least component of the program"s executable code must be loaded into memory as a process. The operating system must then determine when the CPU have the right to be made easily accessible to the process, and also for just how long. When a process controls the CPU, that is instructions will be executed till its allotted time expires, or until it terminates, or until it request an intake or output operation. In the latter case, the operating system will company the I/O request and also suspend the execution that the procedure until the I/O request has actually been satisfied, and also the CPU is once an ext available (on suspension that one process, the CPU is made available to the next waiting process).

In stimulate to have the ability to schedule the execution of multiple processes, the operating mechanism must keep a far-ranging amount of information around each process, including the ar of the procedure in memory, the existing state that the procedure (i.e. running, ready, or blocked), the attend to of the last program instruction executed, and whether or no the procedure is awaiting the completion of one I/O operation.

Memory management

In order because that a procedure to be enforcement by the processor, it must first be loaded into working storage (random access memory, or RAM). In a single-user, single-tasking system, all of the storage not required by the operating mechanism is allocated come the program. In a multi-tasking system, each process requires its very own separate area of memory.

In bespeak to manage the use of memory, the operating mechanism must i have loaded some type of structure that allows it to attend to individual blocks of memory and also allocate them come processes. The system of addressing used and also the dimension of the memory blocks allocated varies from one operating system to another, yet virtually every operating systems use fixed-size blocks of memory, together this simplifies the task of moving data from secondary storage into memory (and vice versa). Memory is allocated to procedures dynamically (as and also when needed), and released when no longer needed.

modern-day operating systems can overcome the limitations of having only a reasonably small lot of functioning memory accessible by making use of disk space to develop virtual memory. Any type of programs loaded right into memory however not currently running deserve to be temporarily relocated from memory and also stored on the computer’s difficult drive. This increases the quantity of memory easily accessible for various other programs, and removes the need for programmers to border the dimension of a program.

Memory monitoring in a multiprogramming device is a facility task. The operating device cannot understand in advancement what program the user will desire to run, and therefore cannot reserve storage for a program. In some cases, there will certainly not be sufficient contiguous memory to fill a brand-new process into a single area that memory, and it will rather be slotted into several different locations.

If there is just not enough totally free memory available to fill the brand-new process, the operating device will have actually to complimentary up enough memory to pack the procedure by temporarily moving one or more other processes out that memory and into virtual memory. To do life even an ext interesting, procedures that room "swapped out" of main memory and into online memory will virtually always it is in loaded right into a completely different area of storage to the one castle were forced to vacate.

The ability to use any easily accessible memory slots, and to swap processes in and also out of memory as and also when necessary, way that a big number the programs have the right to be energetic at the same time (although, because that a solitary processor system, only one procedure at a time is actually running). There is no wasted space, because any cost-free block that memory deserve to be allocated come a process, and the process itself walk not require to have a contiguous block of storage allocated come it in order come run.

The under side is the significant amount that overhead occurs by the operation system due to the should keep track of each process in both memory and also virtual memory. The intricacy is enhanced by the reality that a single process may be scattered across any number of memory locations. The operating mechanism must save track the every part of every process. The must likewise prevent the storage allocated come one procedure from gift overwritten by another process, while at the same time allowing collaborating processes to communicate, and to share usual data and procedures.

record and disk management

Most computer systems employ second storage devices (magnetic disk, magnetic tape, optical media, flash drives etc.) to provide cheap, non-volatile storage because that programs and also data. The programs, and the user data they work with, are held in discrete warehouse units called files. The operating system is responsible because that allocating space for records on second storage media as and also when required.

there is no guarantee the a file, particularly a big file, will be stored in a contiguous place on a physical disk drive. It will really much rely on the lot of room available. The much more full a disc becomes, the an ext likely it is that brand-new files will be created to many locations. As much as the user is concerned, however, the view of the paper presented come them through the operating device will hide the fact that the record has been fragmentized into number of pieces.

The operating mechanism is responsible for keeping track of the location on disk of every item of every paper on the disk. In some cases, that have the right to mean maintaining track of numerous thousands of documents and record fragments on a solitary physical disk. In addition, the operating device must be able to find each document whenever it is required, and carry out read and also write operations on it. The operating device is thus responsible because that the organisation of the record system, for ensuring the read and also write operations to a secondary storage an equipment are secure and reliable, and also for maintaining access times (the time compelled to create data to or check out data from an additional storage) come a minimum.

I/O system monitoring

Input tools are provided to get information into a computer system system, and include peripheral gadgets like the keyboard and also mouse now discovered attached to essentially all computer systems. Output tools receive details from a computer, and include gadgets such together monitors and also printers. Some input and output (I/O) gadgets can be supplied for input and output, consisting of network adapters and secondary storage devices.

The carry of data into or the end of the computer system can take ar one character at a time (e.g. Keyboard input) or in fixed-size blocks (as because that the transport of data between an additional storage and also working memory). In the personal computer solution of the 1980s and 90s, devices such as printers and also disk cd driver were connected to the system’s main circuit board (the mainboard or motherboard) via parallel cables, enabling a number of bits come be sent out along the cable in ~ the exact same time using multiple signal wires.

an ext recently, serial an innovation (in which the data is moved one bit at a time follow me a solitary wire) has improved to such an level that most modern I/O devices, consisting of printers and also disk drives, are linked to the mainboard via a serial cable. Core system materials such as the CPU and also random access memory (RAM) modules room still interconnected via high-speed parallel buses, imposed on the mainboard as combined circuits.

one of the main functions of an operating mechanism is to control accessibility to the input and also output tools attached to the system’s mainboard. It must respond to user keystrokes and also mouse clicks, analyze I/O requests native user applications and also arbitrate once two or an ext processes require the solutions of a an equipment at the very same time. A inquiry for I/O from a user process is signaled come the operating mechanism using a system call (sometimes dubbed a software interrupt).

when a process makes a system call, it properly hands regulate of the processor back to the operating mechanism to allow it to organization the request. Even the operating device itself does no talk directly to hardware devices, however. It will instead pass the inquiry on to the suitable device driver. A an equipment driver is a little program that lives in memory and also does naught until dubbed upon by the operating system. The sole objective is come relay instructions and data between the operating system and a particular hardware device.

This somewhat lengthy chain the command in between a user process and a hardware device serves 2 purposes. First, the accessibility of a vendor-supplied maker driver because that each hardware device means the the operating mechanism itself does not require to recognize the details the every piece of hardware attached to the system, and is therefore device-independent.


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Second, it prevents an application procedure from accessing hardware devices directly, enabling the operating mechanism to arbitrate between applications contending for the same resources.