what characteristic do USB devices and PC CARD HAVE IN COMMON?

Answer 1

USB devices and PC cards are both a set of standards which allow different peripherals to use the same interface. In the case of USB, it's the USB plug, with PC card, it's the design of the card itself. So you could have a PC card device in your PC, take it out, and then put in a different PC card device in the now empty slot.

Second, both USB and PC card devices are designed to be added and removed while the system is running.

There are some devices that are popular with both. There are USB and PC Card based network cards, modems, wireless cards, and portable storage.

USB tends to be more popular with most people, and can support a wider range of devices (like mice, keyboards, TV-output devices, etc) but they both have advantages and disadvantages.