The topic of my final work is "Mobile phone operating systems". In this paper, I will mention all the existing operating systems, and I will process the two largest and widest ones, namely Android and iOS. Android and iOS currently occupy most of the market share in the operating system. If we look at percentages, Android launches almost twice as many devices, but it should be noted that the Android is Open Source system and every mobile device manufacturer can be embedded into their mobile devices while iOS is made exclusively for Apple products under the leadership of the iPhone . Furthermore, I will process the most important for the average user on each device, and these are the apps. Also, I will write to the initiator of everything mentioned above, and these are smart mobile devices, so-called Smartphone. The initial purpose of Smartphone has long been turned into something bigger. They allow us to download apps, from those specialized, types of banking services, to customized weather forecasts, calendars, entertainment applications, GPS navigation and almost everything you want. In this article, I devoted most of my attention to the development of the Android and iOS versions that have made tremendous progress over the years. Both systems have "come close" to the user themselves to measure that there is little room for some significant improvements. The fact that the number of smartphone users from 2014 to 2017 increased from 1.57 billion to 2.32 billion, show how this market has become more advanced and shows the trend of steady growth. It is assumed that by 2020 every other man should own a smartphone, which is a fascinating figure if we take into account how many people in underdeveloped countries do not even have internet access and whether they have a smartphone.