IBM Card Sorter - Sorting Operations

Sorting Operations

Multiple column sorting was commonly done by first sorting the least significant column, then proceeding, column by column, to the most significant column. This is called a least significant digit radix sort.

Numeric columns have one punch in rows 0-9, possibly a sign overpunch in rows 11-12, and can be sorted in a single pass through the sorter. Alphabetic columns have a zone punch in rows 12, 11, or 0, a digit punch in one of the rows 1-9, and can be sorted by passing some or all of the cards through the sorter twice on that column. For more details of punched card codes see Punched card#IBM 80 column punched card format.

There were several methods used for Alphabetical sorting, depending on the features provided by the particular sorter and the characteristics of the data to be sorted. A commonly used method on the 082 and earlier sorters was to sort the cards twice on the same column, first on digit rows 1-9, then on the zone rows 12, 11, and 0 (or vice versa, zone rows first then digit rows). Operator switches allow zone-sorting by "switching off" rows 1-9 for the second pass of the card for each column.

Other special characters and punctuation marks were added to the card code, involving as many as three punches per column (and in 1964 with the introduction of EBCDIC as many as six punches per column). The 083 and 084 sorters recognized these multiple digit or multiple zone punches, sorting them to the error pocket.