0o1

0o1 is a numeric literal used in several programming languages to denote an octal value, meaning a number written in base 8. The prefix 0o (zero followed by the letter o) indicates octal notation, and digits 0 through 7 are valid after the prefix. In octal, the numeral 0o1 represents the decimal value 1. This pattern applies to other octal literals as well, such as 0o7 for 7 and 0o10 for 8.

Languages that support the 0o prefix include Python 3 and JavaScript (ES2015 and later), among others that implement octal literals. The 0o syntax was introduced to make octal numbers explicit and to avoid confusion with decimal numbers or legacy octal representations that used a leading zero. When using octal literals, any attempt to write a digit outside the octal range (8 or 9) is invalid and will typically produce a syntax error.

Beyond representation, octal notation is mainly of historical and practical import in low-level programming tasks, such as bitwise operations, permissions in Unix-like systems, and certain configuration formats. In high-level programming, octal literals are less commonly used for everyday calculations but remain a supported feature in languages that adopt the 0o prefix, including scenarios where octal arithmetic or bitwise masks are relevant.