Digit Zero

0 (Zero) is ASCII code point 48 (0x30), Unicode U+0030, and a printable character in the Digit category. It is the additive identity in mathematics and the character that makes positional notation work — without it, there is no way to distinguish 1 from 10 from 100. In programming, zero is everywhere and overloaded. It is the first array index in C, Java, Python, and most languages. It is falsy in JavaScript, C, and Python — meaning `if (0)` never executes. In shell scripts, an exit code of 0 means success, the opposite of most boolean conventions. Prefixing a number with 0 triggers octal interpretation in C and JavaScript (pre-strict mode), so `parseInt("08")` once famously returned 0 instead of 8. In C, the null terminator `'\0'` is byte value 0x00, not the character 0 at 0x30 — confusing these two will ruin your strings and your afternoon. The concept of zero as a number — not just a placeholder — emerged in India around the 5th century, formalized by Brahmagupta in 628 CE. It reached Europe via Arabic mathematicians centuries later, which is why 0–9 are called Arabic numerals despite their Indian origin. UTF-8 encodes it as a single byte 0x30. Subtracting 0x30 from any ASCII digit byte gives its numeric value — a trick as old as C itself. Unicode classifies it as Nd (Number, Decimal Digit) with the name DIGIT ZERO. It is easily confused with the uppercase letter O (0x4F), which is why programming fonts like Fira Code and JetBrains Mono add a dot or slash through zero.