Bits, Bytes, and Why Files Have Sizes

Hey there! I'm Byte, and I live and breathe binary. Let me show you how computers actually store everything. Every piece of data in a computer — a letter, a pixel, a sound sample — is stored using electricity. A wire is either carrying a signal or it isn't. That gives us exactly two choices: ON or OFF. We write those as 1 and 0. One of these tiny ON/OFF decisions is called a **bit** — short for *binary digit*. One bit by itself can only store two states. That's not enough to represent the letter A! So computers group eight bits together into a **byte**. Eight bits in a row gives us 256 possible combinations (2 to the power of 8 = 256). That's plenty to encode every letter, digit, and common symbol. For example, the letter 'A' is stored as the byte 01000001. Every character you type (for everyday English letters and numbers) takes about one byte. So the word 'HELLO' uses 5 bytes — one byte per letter. Files are just long sequences of bytes saved to storage. A text file with 1,000 characters uses roughly 1,000 bytes. An image needs many more bytes because it stores color information for every single pixel — often millions of pixels. That's why photos are much larger than text files. When bytes pile up, we use bigger units: 1 **kilobyte** (KB) = 1,024 bytes. 1 **megabyte** (MB) = 1,024 kilobytes. 1 **gigabyte** (GB) = 1,024 megabytes. If you get stuck on the activity, come back and re-read this units table! Next time you see a file size, you'll know exactly what it's counting.