.TXT

Plain Text

Introduction

A text file holds characters and nothing else: no fonts, no styles, no pictures. Every operating system can open one, and it is the simplest way to keep notes, logs and data that people need to read. What a text file does depend on is how its characters were turned into bytes, its encoding, and how its lines end.

Software

Structure

A text file has no header and no structure beyond its lines. Today most text is UTF-8, which stores ASCII characters as single bytes and everything else as two to four bytes. Older files may use a legacy code page such as Windows-1252, and a few use UTF-16. The file itself does not say which encoding it uses, except when it starts with a byte order mark.

First bytesMeaning
EF BB BFUTF-8 with a byte order mark
FF FEUTF-16, little-endian
FE FFUTF-16, big-endian

Lines end with a line feed (0A) on Linux and macOS, and with a carriage return and line feed (0D 0A) on Windows. Classic Mac OS used a carriage return (0D) alone.