The ISO/ANSI segment control word (SCW) is expressed in ASCII characters and is 5 bytes in length (see Figure 1). Note that the SCW is different from the code in the IBM® segment descriptor word (SDW). The SDW is the internal data management equivalent of the ISO/ANSI SCW. Only 4 bytes are used by data management, but the user buffer area must accommodate an extra byte to allow for conversion from the ISO/ANSI SCW. The SDW is expressed in binary.
Figure 1. Conversion of ISO/ANSI Segment Control Word to
DS/DBS Segment Descriptor Word