CASE STUDY #1

• Batch Systems- DOS
In MS-DOS, the extension ".bat" signified a file which could be executed by the command interpretor COMMAND.COM, by running line by line as if it was a list of commands to be entered, with some extra batch file specific commands for basic programming functionality, including a GOTO command for changing flow of line execution. The IBM OS/2 operating system supported DOS-style batch files. It also included a version of REXX, which was a more advanced batch file scripting language. IBM and Microsoft started developing this system but during the construction of it broke up after a dispute, as a result of this IBM referred to their MS-DOS like console shell without mention of Microsoft; naming it just DOS, although this seemingly made no difference on the way batch files worked from COMMAND.COM.
OS/2's batch file interpreter also supports an EXTPROC command. This passes the batch file to the program named on the EXTPROC file as a data file. The named program can be a script file; this is similar to the various Unix #! Commands.

• Interactive Systems- Unix Operating System
Unix operating systems are widely used in servers, workstations, and mobile devices.[1] The Unix environment and the client–server program model were essential elements in the development of the Internet and the reshaping of computing as centered in networks rather than in individual computers.
Both Unix and the C programming language were developed by AT&T and distributed to government and academic institutions, which led to both being ported to a wider variety of machine families than any other operating system. As a result, Unix became synonymous with "open systems".
Unix-like systems run on a wide variety of machine architectures. They are used heavily for servers in business, as well as workstations in academic and engineering environments. Free Unix variants, such as GNU/Linux and BSD, are popular in these areas. Some Unix variants like HP's HP-UX and IBM's AIX are designed to run only on that vendor's hardware. Others, such as Solaris, can run on multiple types of hardware, including x86 servers and PCs. Apple's Mac OS X, a hybrid kernel-based BSD variant derived from NeXTSTEP, Mach, and FreeBSD, has replaced Apple's earlier (non-Unix) Mac OS. Unix interoperability was sought by establishing the POSIX standard. The POSIX standard can be applied to any operating system, although it was originally created for various Unix variants.

• Real-time systems- QNX


QNX is based on the idea of running most of the OS in the form of a number of small tasks, known as servers. This differs from the more traditional monolithic kernel, in which the operating system is a single very large program composed of a huge number of "parts" with special abilities. In the case of QNX, the use of a microkernel allows users (developers) to turn off any functionality they do not require without having to change the OS itself; instead, those servers are simply not run. The system is quite small, with earlier versions fitting on a single floppy disk. QNX Software Systems today unveiled the latest generation of its operating system and development tools for the automotive, industrial, medical, networking, and defense markets. Realtime operating system (RTOS) and the QNX Momentics. Tool Suite introduces many new capabilities.

• Hybrid Systems- Linux


Linux is an operating system that was initially created as a hobby by a young student, Linus Torvalds, at the University of Helsinki in Finland. Linus had an interest in Minix, a small UNIX system, and decided to develop a system that exceeded the Minix standards. He began his work in 1991 when he released version 0.02 and worked steadily until 1994 when version 1.0 of the Linux Kernel was released. The kernel, at the heart of all Linux systems, is developed and released under the GNU General Public License and its source code is freely available to everyone. It is this kernel that forms the base around which a Linux operating system is developed. There are now literally hundreds of companies and organizations and an equal number of individuals that have released their own versions of operating systems based on the Linux kernel. More information on the kernel can be found at our sister site, LinuxHQ and at the official Linux Kernel Archives. The current full-featured version is 2.6 (released December 2003) and development continues.
Linux has an official mascot, Tux, the Linux penguin, which was selected by Linus Torvalds to represent the image he associates with the operating system. Tux was created by Larry Ewing and Larry has generously given it to the community to be freely used to promote Linux.


• Embedded Systems--Windows Mobile

Windows Mobile is a mobile operating system developed by Microsoft that was for use in smartphones and mobile devices, but is being phased out to specialized markets.

The current version is called "Windows Mobile 6.5". It is based on the Windows CE 5.2 kernel, and features a suite of basic applications developed using the Microsoft Windows API. It is designed to be somewhat similar to desktop versions of Windows, feature-wise and aesthetically. Additionally, third-party software development is available for Windows Mobile, and software applications can be purchased via the Windows Marketplace for Mobile.

Originally appearing as the Pocket PC 2000 operating system, most Windows Mobile devices come with a stylus pen, which is used to enter commands by tapping it on the screen. Microsoft announced a completely new phone platform, Windows Phone 7, at the Mobile World Congress in Barcelona on February 15, 2010. Phones running Windows Mobile 6.x will not be upgradeable to version 7.

Windows Mobile's share of the Smartphone market has fallen year-on-year,decreasing 20% in Q3 2009. It is the 5th most popular smartphone operating system, with a 5% share of the worldwide smartphone market (after Symbian, BlackBerry OS, Android and iPhone). In the United States, it is the 3rd most popular smartphone operating system for business use (after BlackBerry OS and iPhone), with a 24% share among enterprise users. Microsoft is phasing out Windows Mobile to specialized markets, such as rugged devices, and focusing on its new mobile platform, Windows Phone 7.