If you've ever noticed, Mac OS has its Apple menu on the top left and Windows has its start menu in the bottom left, really for no compelling reason.

如果你注意到，你会发现，Mac操作系统,在其左上角是Apple菜单，Windows却把它的开始菜单,放在左下角，毫无理由可言。

哈佛公开课 - 计算机科学课程节选

But you can look at manuscripts of the early eleventh century and see people singing Ps and Ls and Os and Ms and things like that.

但是大家可以看看,十一世纪初的手稿,可以看到那时有人在唱P,以及L,O和M之类的

耶鲁公开课 - 聆听音乐课程节选