The operating system uses groups of labels to identify magnetic tape volumes and the data sets that they contain. Application programs generally do not use these labels directly. Magnetic tape volumes can have standard or nonstandard labels, or they can be unlabeled. DASD volumes must use standard labels. Standard labels include a volume label, a data set label for each data set, and optional user labels. A volume label, stored at track 0 of cylinder 0, identifies each DASD volume.

International Organization for Standardization (ISO) and the American National Standards Institute (ANSI) tape labels are similar to IBM standard labels. ASCII permits data on magnetic tape to be transferred from one computer to another, even though the two computers can be products of different manufacturers. IBM standard labels are coded in the extended binary-coded-decimal interchange code (EBCDIC). ISO/ANSI labels are coded in the American National Standard Code for Information Interchange (ASCII).