The following text is excerpted verbatim from "An Introduction to ITS for the MACSYMA User" by Ellen Golden, as revised April 14, 1981. ******************************************************************************** IV. Introduction to and Description of Files A file is simply an area on a particular storage device which contains data or text. The only storage devices which are used on the MC machine are disks and tapes. Files on the disks are figuratively grouped into "directories". A directory is just a list of all the files stored under a given name. IV.A. File Names Files in the ITS system possess two names, each of at most 6 characters. They are referenced by giving the two names as well as the device (default is DSK:) and the directory name where the file resides. A device is usually a machine name, meaning the disk of that machine. The device name DSK: refers the disk of the machine you are using. Thus on MC, either DSK: or MC: means MC's disks. A device name is always followed by a colon. A directory name is always followed by a semi-colon. Your directory is determined when you login: if you have a directory of your own, its name will be the same as your login name; otherwise it is the default specified in your INQUIR entry, if one was specified; if none was specified, you will be assigned by the system to a "home directory" called USERSn; where n is a digit from 0 to 9. You may determine which directory you have been assigned to by typing :HSNAME File names are up to six characters long and separated by spaces. A > sign may be used for the second file name and stands for the name which is the largest numerically if there exists a file with the given first name and a numeric second name; otherwise the > sign represents the "greatest" name in an alphanumeric sense. A < sign may be similarly used for the "least" name. The device (followed by a colon), the directory name (followed by a semicolon), and the file names (separated by a space) may appear anywhere in the file descriptor string. Thus for example both INTRO 4 DSK:RAB; RAB;DSK:INTRO 4 are equivalent descriptions. However, the most usual description is DSK:RAB;INTRO 4 Any of the four descriptors (1st name, 2nd name, device, directory) may be omitted and either the default, or the value given in a previous command (if there was one given) will be used. Notice that at DDT level the "usual" way to reference this file is: DSK:RAB;INTRO 4 while in MACSYMA the two file names are given first and then the device and directory, (INTRO, 4, DSK, RAB). i.e. (filename1,filename2,device,directory), which corresponds to the DDT ordering: INTRO 4 DSK:RAB;.