A mobile operating system, also called a mobile operating system, is an operating system that contains programs and data designed to run on mobile devices such as mobile phones, various smartphones, PDAs, different tablets and other portable devices. This article presents a compare and contrast report on Android, iOS, Blackberry and Windows operating systems developed for mobile devices. INTRODUCTION Mobile devices are one of the most used technologies in today's world. It can be seen that in recent years, wireless technologies have developed significantly. Every mobile system needs an operating system to run on that is compatible with the hardware devices it runs on. Each operating system provides its own features and services, such as making calls, sending text messages, taking photos, accessing web pages, etc. Basic mobile operating systems were too simple, because the handsets they ran on had limited capabilities and support. But today's smartphones come with comprehensive features like a computing system, like high-speed CPUs and GPUs, and plenty of storage space. They also provide better quality high resolution multitasking screen and camera etc. Android TECHNOLOGY: It is a software or computing platform and operating system for mobile devices based on the Linux kernel and developed by Google, but later by Open Handset Alliance. (OHA) . This contains the operating system, software and applications and is used in Samsung, HTC Mobile. Android technology is preserved and continually developed by the Android Open Source Project (AOSP). Highlights: • Fully open sources with the best hardware selections. • Multitasking • Frequently improved technology • Excellent user interface • Availability of a large number of applications • .... .. middle of paper ...... very few unexpected interruptions. iOS works great for most of its users. There are very few reports of problems regarding loss of work. Cons such as crashes and freezes are very rare with iOS. • Blackberry: BlackBerry devices keep their email messages secure and protect stored data and include files on the media card. BlackBerry can also help users intelligently manage their applications. Automatic and optional controls can prevent the installation of apps that could harm the BlackBerry and limit what apps can access on devices. • Windows Phone: For security reasons, it is prohibited to do this. For security reasons we cannot use or download any antivirus, it includes its own security applications. Like passwords, authenticator, motion camera, guardian, secure volt, wishes, 4Ureyez only, eWalletGO, etc., we used them to secure our devices from viruses..