Can a PC run without SSD?

[tahirabbasctckhi]

Can a laptop run without SSD?

 

[Colif]

If its the only drive in the PC, well, it will turn on but you can't do anything with it.

You could run off USB but you won't have anything to save anything onto.

 

[jojesa]

Yes.
It could run from a HDD or a USB flash drive, with a Linux live distro or even a Windows USB drive with Windows to Go.
It could also run from a network.
You could be more specific about what you're trying to accomplish.