Enscribe Programmer's Guide

B Block Formats of Structured Files
This appendix describes the block formats for key-sequenced, queue, entry-sequenced, and relative
files. A block in a structured file usually consists of a header, a record area, and a map of offsets
pointing to the beginning of each record. For relative files, an array of record lengths replaces the
offsets map.
Figure 24 (page 170) shows the format 1 block and Figure 31 (page 175) shows the format 2 block.
The data area of a key-sequenced or queue file begins with a bit-map block telling which data
and index blocks are in use. The second block is the root (highest-level) index block for the file.
The third block is either a second-level index block or the file's first data block.
The data area of a relative file also begins with a bit-map block telling which data blocks contain
at least one record. The block immediately following a bit-map block is always the first data block.
For entry-sequenced files, all blocks in the data area are data blocks.
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