Norbert could surf fast but was born unable to move, demonstrating that having a good function is useless if the person is unusable for that function. The CPU in a PC can overheat with long-term or heavy use, reaching temperatures over 75 degrees, so fans are often used to cool PCs. While refrigerators could cool overheating PCs, they would not fulfill the computer's original function. CD-ROMs store software while VCRs record video, but Bob's father misunderstood and thought the CD-ROM could record like a VCR, showing it is important to understand how different technologies function.