for the owner's signon ID is exceeded. Users may request that a file be created on a specific disk volume ($CREATE name VOLUME=name). MTS files fall into one of three categories: public files, user files, and temporary files: Public files are files whose names begin, but do not end, with an asterisk (e.g., *LIBRARY, *USERDIRECTORY). Public files, often called 'star files', are publicly available files that contain programs and data that are widely available to all users. For example, *LIBRARY is a library of commonly used system subroutines. In the earliest days of MTS public files were the only files that could be shared and then only as read-only files. Later, public files could be permitted and shared in the same fashion as any other files. User files are files whose names do not begin with an asterisk or a minus sign. They must be explicitly created ($CREATE) and destroyed ($DESTROY). They are owned by and initially permitted to just the userID that creates them, but they can be permitted for use by other userIDs using the $PERMIT command. To reference a file belonging to another user, the file name is prefixed with the owner's userID followed by a colon (e.g., W163:MYPROGRAM). There are charges for the amount of disk space used and most signon IDs have a maximum disk space limit. Temporary files are files whose names begin with a minus sign (e.g., -TEMP). Their names are unique within a single session. They are created implicitly on first use, are not charged for, do not count against a signon ID's disk space limit, and are automatically destroyed when the terminal or batch session ends. MTS doesn't implement directories, but there is a de facto two-tier grouping of files owing to the inclusion in a file's name of its owner's four-character MTS user ID. File names, like all FDnames, are converted to uppercase before use and so are case-insensitive. File types MTS supports three types of file, line files, sequential files, and sequential with line number files, but line files were by far the most common: Line files Line files ($CREATE name or $CREATE name TYPE=LINE) are line-oriented files which are indexed (and randomly accessible) by line number. Allowed line numbers are ±2147483.647—essentially a signed integer value divided by 1000, but command line references were limited to ±99999.999. Regular writes to a file increase the line number by 1. Lines