History of Computers - Linux
Linux is a Unix-like, low-cost, open-source operating system written in C language. The Linux kernel (core of the operating system that carries out system functions) was created by a University of Helsinki student, Linus Torvalds, in 1991. Linux was originally designed for PCs based on Intel x-86 architecture, but it has since been adapted for more computer hardware platforms than any other operating system.
Overview
The Linux kernel is monolithic, meaning that all the device drivers are part of the kernel; in other words, the kernel controls components like input/output devices, memory, hardware interrupts, file systems, and the CPU stack at the lowest level.
Linux has all the features of Unix and supports the following:
- multitasking: allows several programs to run at the same time
- memory protection: protects against one program bringing the whole system down
- multi-user usage: allows several users on the same machine at the same time
- multithreading: having several, independent threads of control
- virtual memory: maps virtual addresses used by a program into physical addresses in computer memory
- demand loading: only reading into RAM the parts of the program that are necessary
- copy-on-write: if more than one copy of an application is loaded, all tasks can share the same memory; this decreases memory usage and increases speed
- swap space: pages of memory can be written to a reserved area of a disk (the swap space) and treated as an extension of physical memory (RAM); used when the amount of physical RAM available is insufficient
- multiple virtual consoles: allows for up to 64 independent login sessions through the console
- supports a variety of file systems: including minix, Xenix, and V file systems
Linux runs on many different CPUs (not just Intel's) and is used on a wide range of devices: servers, mainframes and supercomputers, desktops, electric keyboards, readers, etc. In fact, more than 90% of today's fastest supercomputers run some form of Linux. Linux even runs on embedded systems, in which the operating system is built into non-volatile memory (such as ROM); for example, it is used on mobile phones (the Android system is built upon the Linux kernel), tablet computers, network routers, televisions, and video game consoles.
The Linux kernel, in combination with many other utilities and applications that together form the complete operating system, is called a distribution. Linux has been packaged into over 300 distributions, with about a dozen for general-purpose use. Popular distributions include Debian (and its derivatives, Linux Mint and Ubuntu), Fedora (and its derivatives, Red Hat and CentOS), Mandriva/Mageia, openSUSE, and Arch Linux.
Linux was released under the GNU General Public License (GPL), which allows people to take free software and distribute their own versions of it with or without charge, as long as they make the source code for their modifications available. Linux is still being developed and managed by the open-source community.
Significance
Linux is an extremely versatile operating system (it can run on such a wide range of devices). It has also proven to be tremendously reliable as a network server, able to run for long periods of time without re-booting and only needing occasional maintence. In addition, its cost-effectiveness makes it one of the most popular operating systems amongst the general public.
Linux is also one of the most widely distributed open-source operating systems, and it was the first operating system that truly caught the public eye with the promise of being open-source. With Linux's open-source distribution, users have the option to compile and build their own kernels or to use a commercial distribution.
