Stanford CS105: Intro to Computers | 2021 | Lecture 1.1 Bits, Bytes, & Binary: It's all about 0 & 1

Computers operate using the binary number system, which differs from the decimal system we commonly use. The decimal system (base 10) uses ten digits (0-9), while the binary system (base 2) uses only two digits: zero and one. All numbers in a computer are represented using these two binary digits.

Computers use binary because their memory consists of electronic switches that can be either on or off, similar to a light switch. An 'off' switch represents a zero, and an 'on' switch represents a one. Each of these single digits (zero or one) is called a 'bit,' which is a shortened form of 'binary digit'.

A single bit offers limited utility, so bits are grouped together. The primary grouping is a 'byte,' which consists of eight bits. The byte is the fundamental unit for measuring computer storage.

All computer data, whether in main memory or other storage mediums, is ultimately stored as bits and bytes. Different storage devices represent these zeros and ones in various ways: SSDs use electronic switches, hard disks use magnetic polarity, and CDs/DVDs/Blu-rays use pits and lands. Regardless of the method, the underlying principle is the representation of information as zeros and ones.