Explanation:

When a new hardware device, such as a printer or scanner, is connected to a computer, it requires specific software to communicate effectively with the operating system and other applications. This essential software is known as a device driver. A driver acts as a translator, converting the operating system's commands into instructions that the hardware device can understand and execute, and vice versa. Without the correct driver, the operating system cannot properly recognize or control the new hardware, rendering it unusable. Option (a) 'buffer' refers to a temporary storage area for data, which is not the primary software needed for device communication. Option (c) 'pager' is a communication device used for sending short messages, completely unrelated to hardware installation. Option (d) 'server' refers to a computer program or a device that provides a service to another computer program and its user, also irrelevant in this context. Therefore, installing the appropriate 'driver' is a prerequisite for using any new peripheral device.