An operating system (OS) is software, consisting of programs and data, that runs on computers and manages computer hardware resources and provides common services for efficient execution of various application software.

The following operating systems and file systems are supported:

• Windows: 7, Vista, XP,  ME, 2000, 98, 95, & all server; NTFS, FAT32, FAT16; using standalone basic partitions or dynamic spanned, striped or fault-tolerant RAID file systems and/or volumes.
• Mac OS/2: FAT and HPFS file systems and/or volumes.
• Linux: Ubuntu, Fedora, Red Hat etc., & all server; ext2, ext3, ext4, xfs, reiserfs, reiser4, jfs;  using standalone basic partitions or dynamic spanned, striped or fault-tolerant RAID file systems and/or volumes.
• Unix.
• Novell Netware: FAT and NSS; using standalone basic partitions or dynamic spanned, striped or fault-tolerant RAID file systems and/or volumes.
• Solaris.
• MS-DOS: FAT 12 or 16 file systems and/or volumes.
• and other systems not mentioned above... (please feel free to enquire)

For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between application programs and the computer hardware, although the application code is usually executed directly by the hardware, but will frequently call the OS or be interrupted by it. Operating systems are found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Examples of popular modern operating systems for personal computers are Microsoft Windows, Mac OS X, and GNU/Linux.

Early computers were built to perform a series of single tasks, like a calculator. Operating systems did not exist in their modern and more complex forms until the early 1960s. Some operating system features were developed in the 1950s, such as monitor programs that could automatically run different application programs in succession to speed up processing. Hardware features were added that enabled use of runtime libraries, interrupts, and parallel processing. When personal computers by companies such as Apple Inc., Atari, IBM and Amiga became popular in the 1980s, vendors added operating system features that had previously become widely used on mainframe and mini computers. Later, many features such as graphical user interface were developed specifically for personal computer operating systems.

An operating system consists of many parts. One of the most important components is the kernel, which controls low-level processes that the average user usually cannot see: it controls how memory is read and written, the order in which processes are executed, how information is received and sent by devices like the monitor, keyboard and mouse, and decides how to interpret information received from networks. The user interface is a component that interacts with the computer user directly, allowing them to control and use programs. The user interface may be graphical with icons and a desktop, or textual, with a command line. Application programming interfaces provide services and code libraries that let applications developers write modular code reusing well defined programming sequences in user space libraries or in the operating system itself. Which features are considered part of the operating system is defined differently in various operating systems. For example, Microsoft Windows considers its user interface to be part of the operating system, while many versions of Linux do not.

In the early 1950s, a computer could execute only one program at a time. Each user had sole use of the computer and would arrive at a scheduled time with program and data on punched paper cards and tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a front panel using toggle switches and panel lights. It is said that Alan Turing was a master of this on the early Manchester Mark 1 machine, and he was already deriving the primitive conception of an operating system from the principles of the Universal Turing machine.

Later machines came with libraries of software, which would be linked to a user's program to assist in operations such as input and output and generating computer code from human-readable symbolic code. This was the genesis of the modern-day operating system. However, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a washing line from which tapes were hung with different coloured clothes-pegs to indicate job-priority.