下列选项中，哪一项不是操作系统的主要功能( )。

Germany invented a spring-powered clock around 1510. It was not very precise. The first clock with a minute hand was invented by Jost Burgi in 1577. It also had problems. The first practical clock was driven by a pendulum. It was developed by Christian Huygens around 1656. By 1600, the pendulum clock also had a minute handA．Dividing the day into hours, minutes,and secondsB．Using the sunC．Dividing the year into months and daysD．Sundial clocksE．Water clocksF．Pendulum clocks