A README file contains information about other files in a directory or archive of computer software. A form of documentation, it is usually a simple plain text file called READ.ME, README.TXT, README.md (for a text file using markdown markup), README.1ST – or simply README. The file's name is generally written in uppercase letters. On Unix-like systems in particular this makes it easily noticed – both because lowercase filenames are more usual, and because traditionally the ls command sorts and displays files in ASCIIbetical ordering, so that uppercase filenames appear first.