Functions of
Operating System:
Process
Management
A process is a program in
execution. A process needs certain resources, including CPU time, memory, files,
and I/O devices, to accomplish its task.
The
operating system is responsible for the following activities in connection with
process management.
1. Process creation and deletion.
2. Process suspension and resumption.
3. Provision of mechanisms for:
process synchronization
process communication
Main-Memory
Management
Memory is a large array of words
or bytes, each with its own address. It is a repository of quickly
accessible data shared by the CPU
and I/O devices.
Main
memory is a volatile storage device. It loses its contents in the case of
system failure.
The
operating system is responsible for the following activities in connections
with memory management:
Keep track of which parts of memory are
currently being used and by whom.
Decide which processes to load when
memory space becomes available.
Allocate and
de-allocate memory space as needed.
File Management
A
file is a collection of related information defined by its creator. Commonly,
files represent programs (both source and object forms) and data.
The operating system is responsible
for the following activities in connections with file management:
File
creation and deletion.
Directory
creation and deletion.
Support
of primitives for manipulating files and directories.
Mapping
files onto secondary storage.
File
backup on stable (nonvolatile) storage media.
I/O
System Management
A buffer-caching system
A general device-driver interface
Drivers for specific hardware
devices
Secondary-Storage
Management
Since
main memory (primary storage) is volatile and too small to accommodate
all data and programs permanently, the computer system must provide secondary
storage to back up main memory.
Most modern computer systems use
disks as the principle on-line storage medium, for both programs and data.
The operating system is responsible
for the following activities in connection with disk management:
Free space management
Storage
allocation
Disk
scheduling
Networking
(Distributed Systems)
A distributed system is a collection
processors that do not share memory or a clock. Each processor has its own
local memory.
The
processors in the system are connected through a communication network.
Communication takes place using a protocol.
A distributed system provides user access to
various system resources.
Access to a shared resource allows:
Computation
speed-up
Increased data availability
Enhanced
reliability
Protection System
system
and user resources.
The protection mechanism must:
distinguish
between authorized and unauthorized usage.
specify
the controls to be imposed.
provide
a means of enforcement.
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