Sorting on a multiple magnetic tape unit

Abstract

Various techniques have been devised for sorting on general purpose computers. Most of these utilize magnetic tape units since they are necessary for storing the large quantities of data handled. The obvious disadvantage of a magnetic tape reel system is the serial nature of the stored information. Once a number of records have been written, considerable time is required to locate the same records again. For this reason, the usual method of sorting via magnetic tape is a process of shuttling the information back and forth from tape to tape, obtaining larger and larger blocks of sorted information until the entire file has been sorted. The disadvantages here are apparent. The excessive handling of data is not only time-consuming but also prone to error. Another technique frequently used is a block sort on the highest-order digit of the sort key. The information is distributed to a number of tape units and later each tape is sorted down to the last digit. For efficient operation ten tape units are required, which adds considerable cost to the system.