DOS Operating System - Windows Operating System

Dos is a single user, single task OS developed by Microsoft for IBM which is a non-graphical line-oriented command- or menu-driven operating system.

DOS Operating System

DOS stands for Disk Operating System. DOS controls the computer's hardware and provides an environment for programs to run. Everything you can do with a GUI can be done at the DOS prompt. There are many flavors of DOS operating system like MS-DOS, PC DOS, DR DOS, FreeDOS, etc. There are two types of commands in DOS, internal and external. Internal commands are part of the command processor, whereas external commands exist as executable files. The entire operating system is small enough to fit on a floppy disk.

Windows Operating System

The journey of Microsoft Windows begins on November 10, 1983, when Windows was introduced as an extension of MS-DOS. Windows is an ideal operating system for a workforce that increasingly relies on notebook computers. The Windows operating system, allows people to manage files and run software programs on desktop and laptop computers. Windows operating system offers a number of new features that help you work smarter and connect faster to the Internet and with others. It is used to run software applications on several types of platforms such as servers, embedded devices and most typically on personal computers. Unlike MS-DOS, Windows operating system allowed users to execute multiple graphical applications at the same time, through cooperative multitasking.

Windows users could switch among several concurrently running applications. It included a set of desktop applications, including the MS-DOS file management program, a calendar, card file, notepad, calculator, clock, and telecommunications programs, which helped users manage day-to-day activities. Though Windows is the most popular and easy to use operating system, patching its innumerable deficiencies and bugs is not quick, easy and reliable. Compare this with open source operating systems where the patches come more slowly, and the patch status can be verified because we have the source code.

UNIX Operating System

UNIX is a multi-user, multi-tasking, machine-independent operating system. Unix operating system is a software development environment developed by researchers at AT & T Bell Labs, one of the largest research facilities in the world. UNIX is the operating system of choice for engineering and scientific workstations. The two most popular variations of UNIX are the AT& T System V based and the Berkeley Standard Distribution (BSD). The underlying philosophy of UNIX is to make every program do one thing well. The output of one program can become the input for another unknown program. Simple tools can be combined to perform complex tasks. Prototyping is creating something small and modifying it incrementally until it is finished. This is one of the advantages of UNIX. Terse commands and messages to reduce typing and screen output is another advantage. A UNIX based system is intrinsically secure because of its design features.

Free Operating System


The OpenBSD project produces a freely available, multi-platform 4.4BSD-based UNIX-like operating system. Emphasis is placed on correctness, security, standardization, and portability. The binaries and the source are free. All parts of OpenBSD have reasonable copyright terms that permit free redistribution. OpenBSD is distributed with a number of third-party software products. The OpenBSD team makes a new release every six months, with target release dates of May 1 and November 1.


FreeBSD is a UN*X-like operating system used by companies, Internet Service Providers, researchers, computer professionals, students and home users all over the world in their work, education and recreation. The goal of the FreeBSD Project is to provide software that can be used for any purpose, without any strings attached. The operating system can be used free of charge, even by commercial users. The full source for the operating system is available for free, and minimum possible restrictions have been placed upon its use, distribution and incorporation into other work. An improvement or bug fix can be submitted freely and it is added to the source tree.

Real Time Operating System

A real time operating system guarantees a certain capability within a specific time frame.

A real time operating system needs the following capabilities:
  • Multitasking
  • Process threads that can be prioritized
  • A sufficient number of interrupt levels
There are two types of real time operating system:
  • Hard real time operating system
  • Soft real time operating system

For example, a real time operating system could be used to ensure that a certain object was available for a robot on an assembly line. In a hard real time operating system, if the calculation for making the object available at the designated time could not be performed, the operating system would terminate with a failure. In a soft real time operating system, the assembly line would continue to function, but the production output might be lower because objects failed to appear at the designated time, causing the robot to be temporarily unproductive.

Even if an operating system doesn't qualify as a real time system, it could have certain characteristics that make it to be considered as a solution to a particular real-time application problem.

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