Digit Four

4 (Four) is ASCII code point 52 (0x34), Unicode U+0034, and a printable character in the Digit category. It is the smallest composite number — the first integer that isn't prime and isn't one — and the first perfect square after the trivial case of 1, making it the point where multiplication starts to fold back on itself. Four pervades the structure of computing at the hardware level. A nibble is four bits, enough to represent a single hexadecimal digit, which is why hex dumps pair so naturally with binary. IPv4 addresses are four octets. A 32-bit integer is four bytes. Four-space indentation is the default in PEP 8, most JavaScript style guides, and countless other conventions — tabs-vs-spaces wars rage, but four is the compromise that the spaces camp grudgingly coalesced around. In networking, the `4` in IPv4 distinguishes the protocol from IPv6, and the two coexist uneasily across the modern internet, connected by translation layers that nobody enjoys debugging. The written form has two competing glyphs: an open top (most handwriting) and a closed top (most typefaces). This split dates back to European manuscript traditions where scribes optimized for different pen strokes. Unlike most digits, there's no universal agreement on which form is canonical — font designers still pick sides. UTF-8 encodes it as 0x34, one byte, same contiguous range. Unicode classifies it as Nd with the name DIGIT FOUR. Confusion risk is low compared to other digits — 4 has few visual doppelgängers in common scripts — though the fullwidth ４ (U+FF14) will appear in CJK text and fail strict ASCII validation without warning.