This is also referred to as PACKED-DECIMAL or COMPUTATIONAL-3 or COMP-3. A numeric encoding scheme used on a mainframe. For example, an unsigned number of 12345 would be stored in memory on the mainframe system as x'F1F2F3F4F5' ( EBCDIC-encoded, zoned-decimal format). If the same number was defined as PACKED (or COMP-3) it would be stored in memory as x'12345F'. In this example the packing of the number reduces the size from five (5) bytes to three (3) bytes. The low-order nibble of the low-order byte is used as the sign. If an arithemetic operation is attempted on a field defined as COMP-3 and the field contains non-numeric characters then a data exception error (S0C7) will ABEND the attempt . Refer to COMP-3 in this glossary or http://www.simotime.com/datapk01.htm for more information.