The PC uses a low-power battery to maintain certain information when the power is off; for example, your BIOS settings, the current date and time, and resource assignment for Plug and Play systems. This battery can take one of several forms:

• On many older PCs. it is a large rectangular box that is attached to the motherboard with wires.
• Some PCs use a battery soldered to the board that looks like a small cylinder. It is not generally detachable.
• Some PCs use a flat round watch battery in a metal holder.
• Some PCs don't appear to have a battery at all. In this case, the battery may be a lithium type that is within one of the other packages (typically the real-time clock package). It may also be an integrated rechargeable Nickel- Cadmium battery (sometimes called an "accumulator'l that is recharged whenever the line power is connected to the machine. These batteries cannot be replaced, although they are rated for a long life (5 to 10 years).