Data Representation

Computers run on electricity. "On" is 1, "Off" is 0. This is Binary.

Number Systems

Binary (Base 2)

Uses only 0 and 1. * Bit: A single 0 or 1. * Byte: 8 bits (e.g., 10110011). * Calculating: $101_2 = (1 \times 4) + (0 \times 2) + (1 \times 1) = 5_{10}$

Hexadecimal (Base 16)

Uses 0-9 and A-F. Used to simplify binary representation (like color codes #FF5733). * $A = 10, B = 11 ... F = 15$ * One Hex digit = 4 Binary bits (a "Nibble").

Character Encoding

How do numbers become text?

1. ASCII: 7-bit code. Only English (e.g., 'A' = 65).
2. Unicode (UTF-8): The standard today. Covers all languages + Emojis (e.g., '🙂').