Binary Digits: On-Bits and Off-Bits

It's amazing, but the seemingly endless potential of computers is based on the two digital states—on and off. The electronic nature of the computer makes it possible to combine these two electronic states to represent letters, numbers, colors, sounds, images, shapes, and much more—even odors. An "on" or off electronic state is represented by a bit, short for ftnary digit. In the binary numbering system (base 2), the on-bit is a 1 and the off-bit is a 0.
Vacuum tubes, transistors, and integrated circuits characterize the generations of computers. Each of these technologies enables computers to distinguish between on and off and, therefore, to use binary logic. Physically, these states are achieved in a variety of ways.
• In RAM, the two electronic states often are represented by the presence or absence of an electrical charge.
• In disk storage, the two states are made possible by the magnetic arrangement of the surface coating on magnetic tapes and disks.