I never got that. Isn't that a terrible way to handle things? Because it means if your connection cuts out or something goes wrong, your machine is either bricked (if a specialist device) or now lacks the software altogether (if a normal PC or tablet). Wouldn't it make more sense to download the new stuff, then delete the old stuff, then install said new stuff? Don't you think? I'm just wondering because Filezilla does this stupid thing for updates.
With normal software this is not a problem like filezilla you only need to reinstall it again to get it working again. The problem is firmware updates does are dangerous if the system has not got a backup most BIOS of pc these days have a secondary BIOS so if something goes wrong you can still access the system. Windows does it differently it needs to restart to copy the new files and then restart again to make everything active thats why some updates you see two times the starting sequence with Windows.
