DDS stands for Data description specifications. It defines data attributes in the file description. PF, LF, DSPF, PRTF, and ICF files use DDS. We can create a file using DDS by following these steps:

1. Write the DDS script for the source member in a source file.
2. Create the file using the CL command for the respective file type.

The left side of the DDS positions 1 through 44 is called positional entries and is available for fixed format entries. This includes the record format name, field name, and length of the field. The right side of the DDS positions 45 through 80 are used for DDS keywords. This includes attributes of record format, files, and fields. The sequence number and form type are optional in DDS. An asterisk in position 8 makes the line a comment line. Position 17 indicates the name entry in positions 19 through 28.

• Name entry R indicates a record format name. (used with All files)
• Blank indicates a field name. (used with All files)
• K indicates a key field name. (used with PF and LF only)
• S indicates a select field name. (used with LF only)
• O indicates an omit field name. (used with LF only)
• J indicates a join specification. (used with Join LF only)
• H indicates a help specification (used with Display file only)

R specified in position 29 indicates that it is a preferred field, and its definition is defined somewhere else. You can enter the DDS source using STRSEU. You create a DDS pf using the CRTPF command, a DDS LF using CRTLF, a DDS Display file using CRTDSPF, a DDS printer file using CRTPRTF, and a DDS ICF file using CRTICFF.