Clocks and Timers in Operating System

Most computers have hardware clocks and timers that provide three basicfunctions: Give the current time Give the elapsed time. Set a timer to trigger operation X at time T These functions are used heavily by the operating system, as well as by time sensitive applications. Unfortunately, the system calls that implement these functions are not … Read more

Network Devices in operating System

Because the performance and addressing characteristics of network I/O differ significantly from those of disk I/O, most operating systems provide a network I/O interface that is different from the read()–write()–seek() interface used for disks. One interface available in many operating systems, including UNIX and Windows, is the network socket interface. Think of a wall socket … Read more

Direct Memory Access in Operating System

For a device that does large transfers, such as a disk drive, it seems wasteful to use an expensive general-purpose processor to watch status bits and to feed data into a controller register one byte at a time—a process termed programmed I/O (PIO). Many computers avoid burdening the main CPU with PIO by offloading some … Read more

Interrupts in Operating System

In many computer architectures, three CPU-instruction cycles are sufficient to poll a device: read a device register, logical–and to extract a status bit, and branch if not zero. Clearly, the basic polling operation is efficient. But polling becomes inefficient when it is attempted repeatedly yet rarely finds a device ready for service, while other useful … Read more

I/O Hardware in Operating System

Computers operate a great many kinds of devices. Most fit into the general categories of storage devices (disks, tapes), transmission devices (network connections, Bluetooth), and human-interface devices (screen, keyboard, mouse, audio in and out). Other devices are more specialized, such as those involved in the steering of a jet. In these aircraft, a human gives … Read more

The WAFL File System in Operating System

Because disk I/O has such a huge impact on system performance, file-system design and implementation command quite a lot of attention from system designers. Some file systems are general purpose, in that they can provide reasonable performance and functionality for a wide variety of file sizes, file types, and I/O loads. Others are optimized for … Read more

The Mount Protocol in operating System

The mount protocol establishes the initial logical connection between a server and a client. In Solaris, each machine has a server process, outside the kernel, performing the protocol functions A mount operation includes the name of the remote directory to be mounted and the name of the server machine storing it. The mount request is … Read more