Linux is an operating system — very much like UNIX — that has become very popular over the last several years.

Operating systems are computer programs. An operating system is the first piece of software that the computer executes when you turn the machine on. The operating system loads itself into memory and begins managing the resources available on the computer. It then provides those resources to other applications that the user wants to execute. Typical services that an operating system provides include:

  • A task scheduler – The task scheduler is able to allocate the execution of the CPU to a number of different tasks. Some of those tasks are the different applications that the user is running, and some of them are operating system tasks. The task scheduler is the part of the operating system that lets you print a document from your word processor in one window while you are downloading a file in another window and recalculating a spreadsheet in a third window.
  • A memory manager – The memory manager controls the system’s RAM and normally creates a larger virtual memory space using a file on the hard disk. (See also this Question of the Day.)
  • A disk manager – The disk manager creates and maintains the directories and files on the disk. When you request a file, the disk manager brings it in from the disk.
  • A network manager – The network manager controls all data moving between the computer and the network.
  • Other I/O services manager – The OS manages the keyboard, mouse, video display, printers, etc.
  • Security manager – The OS maintains the security of the information in the computer’s files and controls who can access the computer.

An operating system normally also provides the default user interface for the system. The standard “look” of Windows 98 includes the Start button, the task bar, etc. The Mac OS provides a completely different look and feel for Macintosh computers.

Linux is as much a phenomenon as it is an operating system. To understand why Linux has become so popular, it is helpful to know a little bit about its history. The first version of UNIX was originally developed several decades ago and was used primarily as a research operating system in universities. High-powered desktop workstations from companies like Sun proliferated in the 1980s, and they were all based on UNIX. A number of companies entered the workstation field to compete against Sun: HP, IBM, Silicon Graphics, Apollo, etc. Unfortunately, each one had its own version of UNIX and this made the sale of software difficult. Windows NT was Microsoft’s answer to this marketplace. NT provides the same sort of features as UNIX operating systems — security, support for multiple CPUs, large-scale memory and disk management, etc. — but it does it in a way that is compatible with most Windows applications.