Android is a mobile operating system initially developed by Android Inc. Android was purchased by Google in 2005.[4] Android is based upon a modified version of the Linux kernel. Google and other members of the Open Handset Alliance collaborated to develop and release Android to the world.[5][6] The Android Open Source Project (AOSP) is tasked with the maintenance and further development of Android.[7] Unit sales for Android OS smartphones ranked first among all smartphone OS handsets sold in the U.S. in the second and third quarters of 2010,[8][9][10] with a third quarter market share of 43.6%.