Both internally and in the interface of the user the utility consists of several distinct modules and tabs, referred to as "displays" in FreeBSD, NetBSD and DragonFly, and "views" in OpenBSD, which are automatically refreshed every specified number of seconds.[5] These modules cover all system components, including statistics resembling vmstat, iostat and netstat in all of the BSDs, as well as pf and sensors views in some of the BSDs.[6][7] The systat utility is notably absent from OS X, where a GUI-based Activity Monitor performs similar functions.