what is operating system(os)?
- An operating system (commonly abbreviated to either OS or O/S) is an interface between hardware and applications; it is responsible for the management and coordination of activities and the sharing of the limited resources of the computer. The operating system acts as a host for applications that are run on the machine.Operating systems offer a number of services to application programs and users.
- Common contemporary operating systems include Microsoft windows, Mac os, LINUX, BSD SOLARIS. Microsoft Windows has a significant majority of market share in the desktop and notebook computer markets, while servers generally run on Linux or other Unix-like systems. Embedded device markets are split amongst several operating systems.
- it is doing Multitasking,Disk access to file systems,Virtual memory allocation,manage device drivers,networking,provide better secutiry and etc.
examples of operating systems and what is contains.
- Microsoft Windows:While the Windows 9x series offered the option of having profiles for multiple users, they had no concept of access privileges, and did not allow concurrent access; and so were not true multi-user operating systems. In addition, they implemented only partial memory protection. They were accordingly widely criticised for lack of security.The Windows NT series of operating systems, by contrast, are true multi-user, and implement absolute memory protection. However, a lot of the advantages of being a true multi-user operating system were nullified by the fact that, prior to Windows Vista, the first user account created during the setup process was an administrator account, which was also the default for new accounts. Though Windows XP did have limited accounts, the
majority of home users did not change to an account type with fewer rights – partially due to the number of programs which unnecessarily required administrator rights – and so most home users ran as administrator all the time. - Windows Vista changes this[3] by introducing a privilege elevation system called User Account Control. When logging in as a standard user, a logon session is created and a token containing only the most basic privileges is assigned. In this way, the new logon session is incapable of making changes that would affect the entire system. When logging in as a user in the Administrators group, two separate tokens are assigned. The first token contains all privileges typically awarded to an administrator, and the second is a restricted token similar to what a standard user would receive. User applications, including the Windows Shell, are then started with the restricted token, resulting in a reduced privilege environment even under an Administrator account. When an application requests higher privileges or "Run as administrator" is clicked, UAC will prompt for confirmation and, if consent is given (including administrator credentials if the account requesting the elevation is not a member of the administrators group), start the process using the unrestricted token.
- Linux/Unix:Linux and UNIX both have two tier security, which limits any system-wide changes to the root user, a special user account on all UNIX-like systems. While the root user has virtually unlimited permission to affect system changes, programs running as a regular user are limited in where they can save files, what hardware they can access, etc. In many systems, a user's memory usage, their selection of available programs, their total disk usage or quota, available range of programs' priority settings, and other functions can also be locked down. This provides the user with plenty of freedom to do what needs done, without being able to put any part of the system in jeopardy (barring accidental triggering of system-level bugs) or make sweeping, system-wide changes. The user's settings are stored in an area of the computer's file system called the user's home directory, which is also provided as a location where the user may store their work, similar to My Documents on a Windows system. Should a user have to install software or make system-wide changes, they must become the root user temporarily, usually with the su or sudo command, which is answered with the computer's root password when prompted. Some systems (such as Ubuntu and its derivatives) are configured by default to allow select users to run programs as the root user via the sudo command, using the user's own password for authentication instead of the system's root password. One is sometimes said to "go root" when elevating oneself to root access.
- Mac OS X:Mac OS X supports HFS+ with journaling as its primary file system. It is derived from the Hierarchical File System of the earlier Mac OS. Mac OS X has facilities to read and write FAT, NTFS (only read, although an open-source cross plataform implementation known as NTFS 3G provides read-write support to Microsoft Windows NTFS file system for Mac OS X users.), UDF, and other file systems, but cannot be installed to them. Due to its UNIX heritage Mac OS X now supports virtually all the file systems supported by the UNIX VFS. Recently Apple Inc. started work on porting Sun Microsystem's ZFS filesystem to Mac OS X and preliminary support is already available in Mac OS X 10.5.
DISCLAIMER:
THIS ALL THE DATA IN FROM WHICH WE FATCH IS ONLY FOR THE LEARNING PURPOSE ONLY AND IT ARE RESPECTIVE RIGHT OF THEIR OWNERS.
HERE PICTURES ARE TAKEN FROM WIKIPEDIA.ORG or any public website.
