OPERATING SYSTEM COMPONENTS
eight major operating system components. They are:
ü A process
can be thought of as a program in execution. A batch job is a process. A time shared user program is a process.
ü A process
needs certain resources-including CPU time, memory, files, and I/O devices-to accomplish its task.
ü A program
by itself is not a process; a program is a passive entity, such as the contents of a file stored on disk, whereas a process is an
active entity, with a program counter specifying the next instruction to
ü A process is the unit of work in
operating system is responsible for the following activities in connection with process management:
and deleting both user and system processes
and resuming processes
mechanisms for process synchronization
mechanisms for process communication
mechanisms for deadlock handling
(ii) Main – Memory
memory is a large array of words or bytes, ranging in size from hundreds of thousands to billions. Each word or byte has its
memory is a repository of quickly accessible data shared by the CPU and I/O
improve both the utilization of the CPU and the speed of the computer's
response to its users, we must keep several programs in memory.
operating system is responsible for the following activities in connection with memory management:
ü Keeping track
of which parts of memory are currently being used and by whom.
(iii) File Management
management is one of the most visible components of an operating system.
operating system is responsible for the following activities in connection with file management:
and deleting files
and deleting directories
primitives for manipulating files and directories
files onto secondary storage
up files on stable (nonvolatile) storage media
ü One of the
purposes of an operating system is to hide the peculiarities of
hardware devices from the user. This is
done using the I/O subsystem.
ü The I/O
subsystem consists of a memory-management component that includes buffering,
caching, and spooling.
ü A general
for specific hardware devices
main memory is too small to
accommodate all data and programs, and
because the data that it holds are lost when power is lost,
the computer system must provide secondary storage tobackupmainmemory.
operating system is responsible for the following activities in connection with disk management:
distributed system is a collection of processors that do not share memory,
peripheral devices, or a clock.
each processor has its own local memory and clock, and the processors
communicate with one another through various communication lines, such as
high-speed buses or networks.
processors in the system are connected through a communication network, which
can be configured in a number of different ways.
processes must be protected from one another's activities. For that purpose, mechanisms ensure that the files, memory segments, CPU, and
other resources can be operated on by only those processes that have gained
proper authorization from the operating system.
is any mechanism for controlling the access of programs, processes, or users to
the resources defined by a computer system.
can improve reliability by detecting latent errors at the interfaces between
ü One of
the most important systems programs for an operating system is the command
ü It is the interface between the user and the
operating systems include the command interpreter in the kernel. Other
operating systems, such as MS-DOS and UNIX, treat the command interpreter as a
special program that is running when a job is initiated, or when a user first
logs on (on time-sharing systems).
commands are given to the operating system by control statements.
ü When a
new job is started in a batch system, or when a user logs on to a time-shared
system, a program that reads and interprets control statements is executed
program is sometimes called the control-card interpreter or the command-line interpreter, and is often known
as the shell.
referred to as real memory or primary memory
2. I/O modules
secondary memory devices
3. System bus
communication among processors,
memory, andI/O modules.