An operating system  is an interface between the user and the computer. It is basically a program, which has the capability of running multiple numbers of applications on the computer. Right from checking the used up memory to viewing a website, it is all done by the OS. It manages both the hardware and software resources of the computer. An OS like Windows enables multitasking where you can open various programs or play games and listen to music on the computer simultaneously. Linux is another popular OS with greater security. But there are a few not-so-popular OS as well, which are barely used by anybody.
– Amiga OS: It is the default OS of Amiga PC’s. Introduced in the year 1985, its older versions were compatible with 16 and 32-bit microprocessor of Motorola 68 k, whereas the more recent ones such as AmigaOS 4 works well on PowerPC processors. It consists of Exec, which is a multitasking kernel, AmigaDOS (Disk operating system), Workbench as a GUI (Graphic User Interface), AmigaShell(Command Line Interface),etc. The main disadvantage is the consumption of a large amount of space for which this OS is hardly used in any PC’s. 
– BeOS: It the operating system designed by the company Be Inc. in the year 1991. To run a BeOS on a system it requires 32 megabytes RAM, x-86 Pentium-class processor, a SCSI CD-ROM or IDE/ATAPI drive, a VESA graphics enabled card, etc. BeOS has many advantages such as clean GUI, good performance, symmetric multiprocessing, memory protection and no viruses to name a few. But the number of disadvantages makes BeOS a less popular operating system. With its substandard website browsers and its ill compatibility with common office documents as Access Database and equally bad hardware support, BeOS has became unviable for use. 
– Windows Me 2000: This millennium product of Microsoft was the successor to the extremely successful Windows 98 and was only developed for personal computers. It consisted of the Internet Explorer 5.5, Windows Movie Maker and Windows Media Player 7 software. The most significant difference of Windows Me from its predecessor (Windows 98) is that it did not include the real address mode Microsoft-DOS. This operating system had a very short life period of only a year after which it was substituted by Windows XP. This is mainly because of its hardware incompatibility. It was very expensive and could not be uninstalled easily (one had to take the pain of formatting the computer to remove Windows Me!!!). 
– JavaOS: This operating system consists of a JVM (Java Virtual Machine). Unlike the other OS that are written in the computer language C, JavaOS was obviously developed mainly in Java by Sun Microsystems. JavaOS was designed to work with embedded systems. Its application lies mainly in ATM’s, networking infrastructure and in set top box. Though this java-based software still finds its use in JavaStation, it is considered as a so-called “legacy system”, which is definitely not used for any application anymore. 
– Lindows: This OS was developed in the year 2001 with the prime objective of running Windows applications on Linux. This compatibility was achieved by using the Software known as Wine. As Linux is a good server side OS but is not as good with desktop, the manufacturers thought that Lindows will be a perfect solution to this problem. But Lindows showed mediocre performance in running Windows application. When Windows is so much user-friendly, why should one bother to use Lindows? (The manufacturers should have answered to that one before investing). 
– OS/360: The first version of OS/360 was developed in the 1960’s by IBM. It was mainly for its mainframe computers. A very vital part of its operation was the DASD (Direct Access Storage Devices). This product did not really attract the customers for a variety of reasons. Firstly, it required a huge amount of memory. Secondly, its price was on the higher side and if anybody could still deal with that, it made the system slow. These reasons were enough for customers to keep away from this software. 
– Windows 1.01: It was introduced during 1980’s. It had GUI (Graphic User Interface) and multitasking-based OS by Microsoft. Though it was the first attempt of Microsoft in this direction, it did not turn out very well. Its competitor, Apple had introduced more advanced products during that time, which left Windows 1.01 far behind. 
– Windows Vista: It was developed in the year 2006 by Microsoft with much fanfare for personal and office PC’s. Vista seemed very promising with its attractive, new features. It had an upgraded GUI, Windows DVD Maker and redesigned audio, print, networking and even search function tools. Vista was a big disappointment due to its hardware as well as software incompatibilities and high cost. It was also very slow. Everybody tries to use upgraded software but with Vista, people preferred downgrading to the tried and tested XP. 
– XTS-400: It is an operating system developed by BAE Systems. It supported multi-user as well as multi-tasking settings. It could work with networked environments. Gigabit Ethernet, IPv6 and IPv4 were also supported by it. It was capable of providing both secured (strictly, for administrative purposes) and not-so–secured environments. For maintaining a highly secured network data flow, this OS can be adopted. Even though XTS-400 has many benefits, it has a large number of disadvantages as well. Limited hardware, no GUI and slower performance are some of its potential risks for which it is not favored. 
– Burroughs MCP: This OS by Burroughs Corporation was developed in the year 1961 using the computer language ESPOL. In the 1960’s it was the first OS that had the multiple microprocessor facility and also brought in the virtual memory in picture. It had everything one required (it was secured and gave good performance) but it did not last very long. Its concepts of virtual memory and symmetric multiprocessing are used in recent computers, which are obviously more dynamic than the MCP. Moreover, ESPOL is not a very structured or robust language, which called for an upgrading.