A mobile operating system also called mobile operating system, is an operating system that contains programs and data designed to run on mobile devices such as cell phones, various smartphones, PDAs, various tablets and other portable devices. This article presents a comparative and contrasting report on Android, iOS, Blackberry and Windows operating systems developed for mobile devices. INTRODUCTION One of the most used technologies in today's world are mobile devices. It can be seen that wireless technologies have developed significantly in recent years. Every mobile system needs an operating system to run on, compatible with the hardware devices it is running on. Each operating system provides its own features and services such as making calls, sending text messages, taking photographs, accessing web pages, and so on. Basic mobile operating systems were too simple, as the phones they ran on had limited capabilities and support. But smartphones today come with all the features of a computer system, such as high-speed CPU and GPU and lots of storage space. They also provide multitasking, high resolution screen and better quality camera, etc. TECHNOLOGY Android: It is a software or computing platform and operating system for mobile devices based on the Linux kernel and is developed by Google, but later by the Open Handset Alliance (OHA). It contains the operating system, software and application and is used in Samsung and HTC mobile devices. Android technology is preserved and continuously developed by the Android Open Source Project (AOSP). Strengths: • Completely open sources with the best hardware selections. • Multi tasking • Often improved technology • Excellent user interface • Availability of a large number of applications •.... ..middle of paper......very few unexpected interruptions. iOS works very well for most of its users. There are very few reports of issues regarding lost work. The inconveniences like crashes and freezes are very few with iOS. • Blackberry: BlackBerry devices keep your email messages secure and protect stored data, including files on your memory card. BlackBerry can also help users intelligently use their apps. Automatic and optional controls can prevent the installation of apps that could harm your BlackBerry and limit the apps they have access to on your devices. • Windows Phone: For security reasons, access to unauthorized apps is prohibited. For security reasons we cannot use or download any antivirus, it includes its own security apps. Like password, authenticator, motion cam, keeper, secure volt, wishkers, solo 4Ureyez, eWalletGO etc., we have used them to protect our devices from viruses.