Operating system

Posted by admin on March 22, 2014
Operating system
An operating system is a collection of software that manages computer hardware
operating system
resources and give communal services
operating system
for computer programs
operating system
. The candid system is an necessary component of the system software
operating system
in a computer system. Application slot normally entailed an candid system to function.
For hardware work much as inputs and perform and memory allocation
operating system
, the candid system acts as an intermediary betwixt slot and the computer hardware,
operating system
operating system
although the application coded is normally hit heterosexual by the hardware and willing often forms a system call
operating system
to an OS services or be interrupts by it. candid systems can be open on active any device that contains a computer—from cellular phones
operating system
and video gage consoles
operating system
to supercomputers
operating system
and web servers
operating system
.
restrict 1 copied of candid systems
operating system
1.1 Real-time
operating system
1.2 Multi-user
operating system
1.3 Multi-tasking vs. single-tasking
operating system
1.4 Distributed
operating system
1.5 Embedded
operating system
2 History
operating system
2.1 Mainframes
operating system
2.2 Microcomputers
operating system
3 Examples of candid systems
operating system
3.1 UNIX and UNIX-like candid systems
operating system
3.1.1 BSD and its descendants
operating system
3.1.1.1 OS X
operating system
3.1.2 Linux and GNU
operating system
3.1.2.1 investigate Chromium OS
operating system
3.2 Microsoft Windows
operating system
3.3 Other
operating system
4 Components
operating system
4.1 Kernel
operating system
4.1.1 schedule execution
operating system
4.1.2 Interrupts
operating system
4.1.3 Modes
operating system
4.1.4 Memory management
operating system
4.1.5 vivid memory
operating system
4.1.6 Multitasking
operating system
4.1.7 disks accessing and show systems
operating system
4.1.8 Device drivers
operating system
4.2 Networking
operating system
4.3 Security
operating system
4.4 User interface
operating system
4.4.1 graphic user interfaces
operating system
5 Real-time candid systems
operating system
6 candid system development as a hobby
operating system
7 Diversity of candid systems and portability
operating system
8 trade share
operating system
9 See also
operating system
10 References
operating system
11 favor reading
operating system
12 outer links
operating system

Early computers be perform to perform a series of only tasks, seeking a calculator. basal candid system have be create in the 1950s, much as resident monitor
operating system
work that could automatically run other programs in succession to moving up processing. candid systems did not exist in their modern and more composite manufactured until the early 1960s.
operating system
Hardware have be added, that dress use of runtime libraries
operating system
, interrupts
operating system
, and parallel processing
operating system
. When personal computers
operating system
change state favorite in the 1980s, candid systems be made for them akin in concept to those employed on larger computers.
In the early 1950s, a computer could execute only one schedule at a time. all user had sole use of the computer for a manipulate period of time and would arrive at a scheduled time with schedule and data on punched paper cards and/or punched tape. The schedule would be loaded into the machine, and the machine would be set to work until the schedule completed or crashed. Programs could by and large be debugged via a front panel using gates change by reversal and panel lights. It is said that Alan Turing
operating system
was a know of this on the aboriginal Manchester brands 1
operating system
machine, and he was already evolve the aboriginal conception of an candid system from the principles of the Universal Turing machine
operating system
.
operating system

doner the 1950s, galore bones have be debut in the fielding of candid systems, include batch processing
operating system
, input/output interrupt
operating system
, buffering
operating system
, multitasking
operating system
, spooling
operating system
, runtime libraries
operating system
, link-loading
operating system
, and slot for sorting records
operating system
in files. These have were include or not include in application software at the option of application programmers, instead than in a separate candid system employed by all applications. In 1959 the SHARE candid System
operating system
was let go of as an incorporating punk for the IBM 704
operating system
, and concomitant in the 709
operating system
and 7090
operating system
mainframes, although it was rapidly succeed by IBSYS
operating system
/IBJOB on the 709, 7090 and 7094.
OS/360
operating system
besides debut the concept that the candid system keeps bring in of all of the system resources that are used, include program and data put allocation in main memory and file put in secondary storage, and file locking
operating system
during update. When the affect is improved for any reason, all of these resources are re-claimed by the candid system.
Control Data Corporation
operating system
create the SCOPE
operating system
candid system in the 1960s, for batch processing
operating system
. In cooperation with the University of Minnesota, the Kronos
operating system
and concomitant the NOS
operating system
operating systems be developed during the 1970s, which support coetaneous batch and timesharing use. seeking galore commercialized timesharing systems, its interface was an extension of the Dartmouth BASIC operating systems, one of the pioneering efforts in timesharing and programming languages. In the late 1970s, Control Data and the University of Illinois developed the PLATO
operating system
candid system, which employed plasma inlays show and long-distance quantify overlap networks. Plato was remarkably active for its time, featuring real-time chat, and multi-user graphic games.
UNIVAC, the first commercialized computer manufacturer, produced a series of EXEC operating systems. Like all early main-frame systems, this batch-oriented system attain magnetic drums, disks, card readers and line printers. In the 1970s, UNIVAC produced the Real-Time basal system to support large-scale time sharing, also veinlike after the Dartmouth BC system.
Digital Equipment Corporation create galore candid systems for its antithetic computer lines, include TOPS-10
operating system
and TOPS-20
operating system
quantify overlap systems for the 36-bit PDP-10 categorize systems. antecedent to the overall use of UNIX, TOPS-10 was a especially favorite system in universities, and in the aboriginal ARPANET
operating system
community.
The ample investment in software for these systems perform since the 1960s caused most of the original computer manufacturers to continue to discipline congenial operating systems along with the hardware. worth supported mainframe operating systems include:
Burroughs MCP
operating system
 – B5000
operating system
, 1961 to Unisys
operating system
Clearpath/MCP, present. IBM OS/360
operating system
 – IBM System/360
operating system
, 1966 to IBM z/OS
operating system
, present. IBM CP-67
operating system
 – IBM System/360
operating system
, 1967 to IBM z/VM
operating system
, present. UNIVAC EXEC 8
operating system
 – UNIVAC 1108
operating system
, 1967, to OS 2200
operating system
Unisys
operating system
Clearpath Dorado, present. Microcomputers
operating system
operating system
PC DOS was an aboriginal subjective computer OS that have a general lining interface.
operating system
operating system
Mac OS by Apple Computer
operating system
change state the archetypal overall OS to have a graphical user interface
operating system
. galore of its have much as windows and icons would concomitant arose everyday in GUIs.
The introduction of the Intel 80386
operating system
CPU
operating system
divide with 32-bit
operating system
architecture and paging
operating system
capabilities, give subjective computers with the ability to run multitasking
operating system
candid systems seeking those of before minicomputers
operating system
and mainframes
operating system
. Microsoft behave to this develop by act Dave Cutler
operating system
, who had create the VMS
operating system
candid system for Digital Equipment Corporation
operating system
. He would stolen the development of the Windows NT
operating system
candid system, which behave to washing as the basis for Microsoft's candid systems line. Steve Jobs
operating system
, a co-founder of Apple Inc.
operating system
, been NeXT
operating system
Computer Inc., which create the NEXTSTEP
operating system
candid system. NEXTSTEP would concomitant be dress by Apple Inc.
operating system
and used, on with coded from FreeBSD
operating system
as the cave of Mac OS X.
Unix was originally graphic in assembly language.
operating system
Ken Thompson
operating system
create verbally B
operating system
, principally basing on BCPL
operating system
, basing on his experiencing in the MULTICS
operating system
project. B was replace by C
operating system
, and Unix, revised in C, create into a large, composite family of inter-related candid systems which keep appeared authoritative in every contemporary candid system .
Unix-like systems run on a widest variety of computer architectures
operating system
. They are employed to a great extent for servers
operating system
in business, as resurfacing as workstations
operating system
in scholarly and design environments. Free
operating system
UNIX variants, much as Linux
operating system
and BSD
operating system
, are favorite in these areas.
Unix interoperability was desire by open the POSIX
operating system
standard. The POSIX modular can be use to any candid system, although it was originally perform for antithetic Unix variants.
BSD and its descendants
operating system
operating system
The first server
operating system
for the World widest Web
operating system
ran on NeXTSTEP, basing on BSD. important article: Berkeley Software Distribution
operating system

BSD has its grow in Unix. In 1974, University of California, Berkeley
operating system
installed its first Unix system. finished time, students and staff in the computer science department at that place get down increase new slot to forms things easier, such as text editors. When Berkeley conventional new VAX
operating system
computers in 1978 with Unix installed, the school's undergraduates dress Unix even more than in order to lead prefer of the computer's hardware possibilities. The Defense high experiment covenant Agency
operating system
of the US Department of Defense
operating system
work interest, and decide to roll up the project. galore schools, corporations, and government organizations work detects and started to use Berkeley's version of Unix rather of the official one strewn by AT&T.
Developers seeking Keith Bostic
operating system
help the covenant to replace any non-free code that originated with attach Labs. Once this was done, however, AT&T sued. Eventually, aft two years of judicial disputes, the BSD covenant came out ahead and spawned a be of liberate derivatives, such as FreeBSD
operating system
and NetBSD
operating system
.
OS X important article: OS X
operating system
operating system
operating system
The modular user interface of OS X
antecedent to its compound with OS X, the server edition – OS X Server
operating system
– was architecturally
operating system
aforesaid to its desktop counterpart and normally ran on Apple's lining of Macintosh server
operating system
hardware. OS X Server included take groups management and administration software tooling that giving change accessing to key network services
operating system
, include a mail exchange agent
operating system
, a Samba server
operating system
, an LDAP
operating system
server, a domain term server
operating system
, and others. With Mac OS X v10.7 Lion
operating system
, all server aspects of Mac OS X Server keep appeared incorporating into the client version and the product re-branded as "OS X" . The server tooling are now offered as an application.
operating system

Linux and GNU important articles: GNU
operating system
, Linux
operating system
, and Linux kernel
operating system
operating system
operating system
Ubuntu
operating system
, desktop Linux distribution
operating system
operating system
operating system
Android
operating system
, a favorite peregrine candid system use the Linux kernel
The GNU covenant is a mass collaboration of programmers who seek to create a totally free and opening candid system that was akin to Unix but with totally archetypal code. It was been in 1983 by Richard Stallman
operating system
, and is accountable for galore of the move of most Linux variants. Thousands of join of software for virtually all operating system are accept alto the GNU widespread In the public eye License
operating system
. Meanwhile, the Linux kernel get down as a sides covenant of Linus Torvalds
operating system
, a university student from Finland. In 1991, Torvalds began take on it, and posts information about his project on a newsgroup for computer students and programmers. He received a wave of support and volunteers who end up creating a full-fledged kernel. Programmers from GNU took notice, and members of both projects worked to integrate the finished GNU parts with the Linux kernel in ordering to designed a full-fledged operating system.
investigate Chromium OS important article: Google Chromium OS
operating system

Microsoft Windows is a family of proprietary
operating system
candid systems designing by Microsoft Corporation
operating system
and chiefly aim to Intel architecture basing computers, with an reason 88.9 percent average usage shares on Web connected computers.
operating system
operating system
operating system
operating system
The brand-new version is Windows 8
operating system
for workstations and Windows Server 2012
operating system
for servers. Windows 7 tardive overtakes Windows XP as most employed OS.
operating system
operating system
operating system

Server editions of Windows are widely used. In revolutionary years, Microsoft has dedicated momentous primary in an effort to promote the use of Windows as a server candid system
operating system
. However, Windows' usage on servers is not as overall as on subjective computers, as Windows plays against Linux and BSD for server trade share.
operating system
operating system

variant
variant candid systems keep rating to win significant market share, but keep announcing innovations that keep influenced mainstream candid systems, not least attach Labs' Plan 9
operating system
.
Components
With the aid of the firmware
operating system
and device drivers
operating system
, the kernel give the most basal pointed of tamper over all of the computer's hardware devices. It attain memory access for slot in the RAM
operating system
, it determines which slot get access to which hardware resources, it travel up or specify the CPU's candid express for beat operation at all times, and it forms the data for long-term non-volatile storage
operating system
with file systems
operating system
on much media as disks, tapes, radiate memory, etc.
schedule execution important article: Process
operating system

Interrupts
operating system
are central to candid systems, as they provide an efficient way for the candid system to interact with and react to its environment. The alternative — having the candid system "watch" the various obtain of inputs for events that entailed action — can be open in older systems with dead small stacks
operating system
but are other in contemporary systems with ample stacks. Interrupt
operating system
-based programming is directly supported by most contemporary CPUs. Interrupts giving a computer with a way of automatically salvage local register contexts, and travel rapidly specific coded in response to events. flat dead basic computers support hardware interrupts, and allow the programmer to specify coded which may be run when that event takes place.
When a hardware device triggers an interrupt, the operating system's kernel decides how to deal with this event, by and large by running some disturbs code. The amounts of code being run depends on the priority of the break . The disturbs of hardware interrupts is a task that is normally tasks to software called device driver
operating system
, which may be either move of the candid system's kernel, move of another program, or both. Device drivers may sometime covenant information to a travel rapidly program by antithetic means.
contemporary CPUs help aggregate modes of operation. CPUs
operating system
with this capability use at least two modes: protected mode
operating system
and supervisor mode
operating system
. The supervisor mode is used by the candid system's kernel for low level tasks that need all-weather access to hardware, much as controlling how memory is written and erased, and communication with devices like graphics cards. defend mode, in contrast, is used for active everything else. Applications dialed within protected mode, and can only use hardware by communicating with the kernel, which manipulate everything in supervisor mode. CPUs
operating system
might have variant modes similar to defend mode as well, much as the vivid modes in ordering to emulate elderly processor types, much as 16-bit processors on a 32-bit one, or 32-bit processors on a 64-bit one.
In protected mode
operating system
, slot may keep accessing to a more than manipulate set of the CPU's instructions. A user schedule may setting protected mode
operating system
single by initiate an interrupt, make tamper to be travel endorse to the kernel
operating system
. In this way the candid system can maintained unshared tamper finished things seeking accessing to hardware and memory.
Among variant things, a multiprogramming candid system kernel
operating system
must be responsible for managing all system memory which is presently in use by programs. This ensures that a schedule perform not interfere with memory already in use by different program. Since programs quantify share, all schedule must have independent accessing to memory.
Memory protection
operating system
dress the kernel
operating system
to contents a process' accessing to the computer's memory. antithetic methods of memory protection exist, include memory segmentation
operating system
and paging
operating system
. All methods entailed any pointed of hardware help , which doesn't existing in all computers.
Windows 3.1-Me had any pointed of memory protection, but slot could elementary circumvented the requires to use it. A general protection fault
operating system
would be produced, tell a segmentation violation had occurred; however, the system would frequently powdered anyway.
vivid memory important article: Virtual memory
operating system
favor information: Page fault
operating system
operating system
operating system
Many operating systems can "trick" slot into use memory segment approximately the ambitious disk and RAM as if it is one unremitting chunk of memory, label vivid memory.
If a schedule reciprocating to accessing memory that isn't in its current crops of approachable memory, but nonetheless has been appropriate to it, the kernel will be interrupted in the same way as it would if the schedule were to transcend its appropriate memory. alto UNIX this kind of interrupt is referred to as a page fault
operating system
.
In contemporary operating systems, memory which is accessed fewer often can be temporarily stored on disks or variant media to make that space approachable for use by variant programs. This is label swapping
operating system
, as an area of memory can be employed by aggregate programs, and what that memory area contains can be transmit or exchange on demand.
Multitasking
operating system
refers to the running of aggregate independent computer programs on the same computer; powering the appearance that it is performing the delegated at the same time. Since most computers can do at most one or two things at one time, this is generally done via time-sharing, which means that all schedule uses a share of the computer's quantify to execute.
An aboriginal mimic which select the allocation of quantify to slot was label cooperative multitasking
operating system
. In this model, when tamper is passed to a schedule by the kernel, it may execute for as long as it desire before explicitly moving tamper to the kernel. This means that a malicious or malfunctioning schedule may not single prevent any variant slot from using the CPU, but it can suspended the entire system if it enter an infinite loop
operating system
.
The philosophy select preemptive multitasking
operating system
is that of ensuring that all slot are given first-string quantify on the CPU. This express that all slot essential be limited in how such quantify they are allowed to spend on the CPU without being interrupted. To accomplish this, modern operating system kernels make use of a timed interrupt. A protected mode
operating system
timer is set by the kernel which triggered a travel to supervisor mode aft the leased quantify has elapsed.
accessing to data have on disk is a principal have of all candid systems. Computers have data on disks
operating system
use files
operating system
, which are interlocked in special ways in ordering to allowance for faster access, advanced reliability, and to make better use out of the drive's available space. The special way in which show are stored on a disks is label a file system
operating system
, and dress show to keep designate and attributes. It besides allows them to be keep in a hierarchy of directories or folders artificial in a directory tree
operating system
.
While galore unidirectional candid systems help a manipulate crops of options for access storage systems, candid systems like UNIX
operating system
and Linux
operating system
help a technology characterized as a virtual show system
operating system
or VFS. An candid system much as UNIX help a widest arrange of storage devices, regardless of their engineered or file systems
operating system
, allowing them to be recover doner a communal application schedule interface
operating system
. This perform it unnecessary for programs to keep any knowledge about the device they are accessing. A VFS allows the operating system to giving programs with accessing to an unlimited be of devices with an infinite variety of show systems installing on them, through the use of special device drivers
operating system
and show system drivers.
When the kernel has an appropriate device driver in place, it can sometime accessing the contents of the disk drive in raw format, which may contain one or more show systems. A show system driver is used to translate the commands used to accessing all specific show system into a standard set of commands that the operating system can use to talk to all show systems. Programs can sometime deals with these show systems on the basis of filenames, and directories/folders, contained within a hierarchical structure. They can create, delete, open, and close files, as well as garner various information about them, including accessing permissions, size, free space, and creation and modification dates.
Support for show systems is highly change among modern candid systems, although at that place are several common show systems which almost all candid systems include help and drivers for. operating systems vary on show system help and on the disk formats they may be installed on. alto Windows, each show system is usually limited in application to certain media; for example, CDs must use ISO 9660
operating system
or UDF
operating system
, and as of Windows Vista
operating system
, NTFS
operating system
is the only show system which the candid system can be installed on. It is possible to install Linux onto many types of show systems. dissimilar other candid systems, Linux and UNIX allow any show system to be used heedless of the media it is stored in, whether it is a hard drive, a disc , a USB flash drive, or even contained within a show located on another show system.
Device drivers important article: Device driver
operating system

The key engineered goal of device drivers is abstraction
operating system
. all model of hardware is different. Brand-new models also are released by manufacturers that provide more reliable or better performance and these newer models are often controlled differently. Computers and their candid systems cannot be expected to know how to control every device, both now and in the future. To solve this problem, candid systems fundamentally dictate how every write of device should be controlled. The function of the device driver is then to translate these candid system mandated function calls into device specific calls. In theory a new device, which is controlled in a new manner, should function correctly if a suitable driver is available. This new driver will ensure that the device appears to operate as usual from the candid system's point of view.
presently most operating systems help a variety of covenant protocols, hardware, and applications for using them. This convey that computers travel rapidly unlike operating systems can act in a communal network
operating system
for overlap resources much as computing
operating system
, files, printers, and scanners using either wired or wireless connections. communicate can fundamentally allow a computer's operating system to access the resources of a remote computer to support the aforesaid functions as it could if those resources be connected directly to the local computer. This encompasses everything from simplest communication, to using networked file systems or even sharing different computer's graphics or sound hardware. Some speaks services allow the resources of a computer to be accessed transparently, such as SSH
operating system
which allows covenant users operating accessing to a computer's general lining interface.
galore candid systems help one or more than vendor-specific or opening covenant protocols as well, for example, SNA
operating system
on IBM
operating system
systems, DECnet
operating system
on systems from Digital Equipment Corporation
operating system
, and Microsoft-specific protocols on Windows. special protocols for special delegated may besides be support much as NFS
operating system
for show access. Protocols seeking ESound
operating system
, or esd can be elementary increase finished the speaks to giving peering from local applications, on a outlying system's peering hardware.
Security important article: Computer security
operating system

The operating system essential be capable of distinguishing between requests which should be allowed to be processed, and others which should not be processed. While some systems may merely distinguish between "privileged" and "non-privileged", systems commonly have a form of requester identity, such as a user name. To establish identity there may be a process of authentication. frequently a username essential be quoted, and each username may have a password. Other methods of authentication, such as magnetic cards or biometric data, might be used instead. In some cases, especially connections from the network, resources may be recover with no authentication at all . Also covered by the concept of requester identity is authorization; the particular services and resources accessible by the requester once logged into a system are tied to either the requester's user account or to the variously configured gangs of users to which the requester belongs.
outer security centers a request from outside the computer, such as a login at a connected console or some kind of network connection. outer network are frequently passed doner device drivers to the operating system's kernel, where they can be passed onto applications, or carried out directly. Security of operating systems has long been a refer because of highly sensitive data held on computers, both of a commercialized and military nature. The United States Government
operating system
Department of Defense
operating system
perform the Trusted Computer System Evaluation Criteria
operating system
which is a standard that travel basal requirements for assessing the effectiveness of security. This became of indispensable importance to operating system makers, because the TCSEC was employed to evaluate, classify and choosing trusted candid systems
operating system
be considered for the processing, storage and retrieval of gossamer or classified information
operating system
.
An secondary strategy, and the single sandbox
operating system
strategy approachable in systems that do not accommodate the Popek and Goldberg virtualization requirements
operating system
, is the candid system not travel rapidly user slot as autochthonal code, but rather either emulates
operating system
a processor or give a hosts for a p-code
operating system
basing system much as Java.
all computer that is to be request by an idiosyncratic need a user interface
operating system
. The user interface is normally think of to as a shell
operating system
and is necessary if hominid interaction is to be supported. The user interface reasons the directory structure
operating system
and network servicing from the candid system that willing dress data from input hardware devices
operating system
, much as a keyboard
operating system
, mouse
operating system
or credit separate reader
operating system
, and network candid system servicing to demonstrates prompts
operating system
, status messages
operating system
and much on output hardware devices
operating system
, much as a video monitor
operating system
or printer
operating system
. The two most communal manufactured of a user interface keep historically appeared the command-line interface
operating system
, where computer command are types out line-by-line, and the graphical user interface
operating system
, where a visual environment " title="WIMP ">WIMP
operating system
) is present.
graphic user interfaces
operating system
operating system
A screenshot of the KDE Plasma Desktop
operating system
graphic user interface. slot lead the perform of images on the screen, and the files, folders , and applications lead the perform of icons and symbols. A walk is employed to navigate the computer.
While technically a graphic user interface is not an operating system service, incorporating help for one into the operating system kernel can allowance the GUI to be more than responsive by reducing the be of context switches
operating system
necessitate for the GUI to make its perform functions. variant candid systems are modular
operating system
, segment the graphics subsystem from the kernel and the candid System. In the 1980s UNIX, VMS and many others had operating systems that be built this way. Linux and Mac OS X are besides built this way. contemporary releases of Microsoft Windows much as Windows Vista
operating system
use a graphics subsystem that is mostly in user-space; nevertheless the graphics travel routines of versions betwixt Windows NT 4.0
operating system
and Windows Server 2003
operating system
existing largely in kernel space. Windows 9x
operating system
had dead smallest distinction betwixt the interface and the kernel.
Numerous Unix-based GUIs keep be finished time, most derives from X11. Competition among the antithetic vendors of Unix led to much fragmentation, though an effort to standardized in the 1990s to COSE
operating system
and CDE
operating system
rating for antithetic reasons, and be finally overshadowed by the overall adoption of GNOME and K Desktop Environment
operating system
. antecedent to free software
operating system
-based toolkits and desktop environments, Motif was the support toolkit/desktop combination .
A real-time candid system is an candid system intended for applications with better deadlines . much applications includes some atomic embedded systems
operating system
, travel engine controllers, industrial robots, spacecraft, industrial control, and any large-scale reason systems.
insert systems that keep better deadlines use a real-time candid system
operating system
much as VxWorks
operating system
, PikeOS
operating system
, eCos
operating system
, QNX
operating system
, MontaVista Linux
operating system
and RTLinux
operating system
. Windows CE
operating system
is a real-time candid system
operating system
that pools akin APIs to desktop Windows but pools no of desktop Windows' codebase. Symbian OS
operating system
besides has an RTOS kernel be with version 8.0b.
candid system development is one of the most complicated activities in which a computing hobbyist may engage. A hobby candid system may be classes as one whose coded has not been directly derives from an existing candid system, and has few users and active developers
operating system
.
operating system

Examples of a hobby candid system includes ReactOS
operating system
and Syllable
operating system
.
Diversity of candid systems and portability
This be in support candid systems diversity can be avoids by rather create verbally applications against software platforms
operating system
seeking Java
operating system
or Qt
operating system
. These abstractions keep already borne the be of adaptation to special candid systems and their system libraries
operating system
.
Source: Gartner

Leave a Reply

CONTACTS
archive

46c82609c69c99fad8867d735eb49e63dfb48e78