An operating system is the software on a computer that manages the way different programs use its hardware, and regulates the ways that a user controls the computer. It is considered the backbone of a computer, managing both software and hardware resources. Operating systems are responsible for everything from the control and allocation of memory to recognizing input from external devices and transmitting output to computer displays. They also manage files on computer hard drives and control peripherals, like printers and scanners. Some popular modern operating systems for personal computers include Microsoft Windows, Mac OS X, and Linux.

Key features of Linux Operating System:

Following are the key features of the Linux operating system:

• Multitasking: several programs running at the same time.
• Multiuser: several users on the same machine at the same time (and no two-user licenses!).
• Multiplatform: runs on many different CPUs, not just Intel.
• Multiprocessor/multithreading: it has native kernel support for multiple independent threads of control within a single process memory space.
• It has memory protection between processes, so that one program can't bring the whole system down.
• Demand loads executables: Linux only reads from disk those parts of a program that are actually used.
• Shared copy-on-write pages among executables. This means that multiple process can use the same memory to run in. When one tries to write to that memory, that page (4KB piece of memory) is copied somewhere else. Copy-on-write has two benefits: increasing speed and decreasing memory use.
• Virtual memory using paging (not swapping whole processes) to disk: to a separate partition or a file in the file system, or both, with the possibility of adding more swapping areas during runtime (yes, they're still called swapping areas). A total of 16 of these 128 MB (2GB in recent kernels) swapping areas can be used at the same time, for a theoretical total of 2 GB of useable swap space. It is simple to increase this if necessary, by changing a few lines of source code.
• A unified memory pool for user programs and disk cache, so that all free memory can be used for caching, and the cache can be reduced when running large programs.
• All source code is available, including the whole kernel and all drivers, the development tools and all user programs; also, all of it is freely distributable. Plenty of commercial programs are being provided for Linux without source, but everything that has been free, including the entire base operating system, is still free.
• Multiple virtual consoles: several independent login sessions through the console, you switch by pressing a hot-key combination (not dependent on video hardware). These are dynamically allocated; you can use up to 64.
• Supports several common file systems, including minix, Xenix, and all the common system V file systems, and has an advanced file system of its own, which offers file systems of up to 4 TB, and names up to 255 characters long.
• Many networking protocols: the base protocols available in the latest development kernels include TCP, IPv4, IPv6, AX.25, X.25, IPX, DDP (AppleTalk), Netrom, and others. Stable network protocols included in the stable kernels currently include TCP, IPv4, IPX, DDP, and AX.25.