What is the maximum number of IDE devices that can be installed if a system has two IDE channels and a PCI card providing four additional channels?

The maximum number of IDE (Integrated Drive Electronics) devices that can be installed is determined by the number of channels available and the fact that each channel can support two devices. In this scenario, the system has two built-in IDE channels. Each of these two channels can accommodate two devices, which gives a total of four devices from the built-in channels.

Moreover, a PCI card is providing four additional IDE channels. Similar to the built-in channels, each of these additional channels can also support two devices. Therefore, the four additional channels can accommodate eight devices (4 channels x 2 devices per channel).

To determine the overall capacity, add the number of devices that can be supported by the built-in channels (4 devices) to the number supported by the additional channels (8 devices). This results in a total of 12 devices (4 + 8).

The correct answer reflects the total number of IDE devices that can be installed within this system configuration.