If a PC boots first to the hard drive before checking the floppy disk for an OS how do you change this sequence so that if first on the floppy disk for an OS?

To do this you need to go to boot menu .

It depends on configuration of your computer .There are 4 ways to go to boot menu 'f2','del','f8','f12'.

press these buttons before your computer start booting with hard disk. then you will see a blue (most probably if you are using INTEL) then go to boot option and select CD drive or floppy drive as first boot device and then save changes and then restart the computer.

That is all