Exa

Exa is a prefix in the International System of Units (SI) representing 10^18, or one quintillion. The symbol for this prefix is E. It sits between peta (10^15) and zetta (10^21) in the SI prefix series and is used to express very large quantities across various fields. In decimal-based conventions, an exabyte equals 10^18 bytes, and an exajoule equals 10^18 joules. The prefix was standardized as part of the SI in 1960 and is commonly seen in contexts such as data storage, energy, and computing performance. The name and symbol follow the established pattern for SI prefixes.

In computing and information technology, exa- is frequently encountered in discussions of scale and capacity. Terms such as exabyte (EB), exbibyte (EiB, though based on binary prefixes), and exaflop (a measure of computational speed) illustrate how exa- denotes extremely large quantities. The concept of exascale computing refers to systems capable of approximately one exaFLOP of processing power, highlighting the relevance of the prefix for modern high-performance computing.

exa is also the name of a modern command-line tool designed to replace the traditional ls command on Unix-like systems. Written in a systems programming language, exa emphasizes readability and usability, offering colorized output, file-type indicators, optional icons, and Git status integration. It supports features such as recursive listing with a tree view, improved sorting and filtering, and cross-platform availability on Linux and macOS, with ports or equivalents on other systems. This exa aims to provide a more visually informative and ergonomic directory listing experience while maintaining compatibility with common shell workflows.