The basic building elements of a computer are two-state electronic devices. Two-state means either being on or off. The “off” state may correspond to the digit 0 and the “on” may correspond to the digit 1. Thus, whether the data are text, image, audio, or video, everything inside computers is represented using the binary digits 0 and 1. Note that programs can be seen as data describing instructions that tell the computer what to do.

A Binary digIT is abbreviated as a bit. The number of bits needed to store data is referred to as the data size. A byte is 2³ (eight) bits. A kilobyte (KB) is 2¹⁰ (1024, approximately 1 thousand) byte. A megabyte (MB) is 2²⁰ (approximately 1 million) byte. A gigabyte (GB) is 2³⁰ (approximately 1 billion) byte. A terabyte (TB) is 2⁴⁰ (approximately 1 trillion) byte.