74 lines
3.8 KiB
INI
74 lines
3.8 KiB
INI
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Database file structure
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The structure of a dBASE III database file is composed of a header
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and data records. The layout is given below.
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dBASE III DATABASE FILE HEADER:
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+---------+-------------------+---------------------------------+
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| BYTE | CONTENTS | MEANING |
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+---------+-------------------+---------------------------------+
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| 0 | 1 byte | dBASE III version number |
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| | | (03H without a .DBT file) |
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| | | (83H with a .DBT file) |
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+---------+-------------------+---------------------------------+
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| 1-3 | 3 bytes | date of last update |
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| | | (YY MM DD) in binary format |
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+---------+-------------------+---------------------------------+
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| 4-7 | 32 bit number | number of records in data file |
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+---------+-------------------+---------------------------------+
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| 8-9 | 16 bit number | length of header structure |
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+---------+-------------------+---------------------------------+
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| 10-11 | 16 bit number | length of the record |
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+---------+-------------------+---------------------------------+
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| 12-31 | 20 bytes | reserved bytes (version 1.00) |
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+---------+-------------------+---------------------------------+
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| 32-n | 32 bytes each | field descriptor array |
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| | | (see below) | --+
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+---------+-------------------+---------------------------------+ |
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| n+1 | 1 byte | 0DH as the field terminator | |
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+---------+-------------------+---------------------------------+ |
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A FIELD DESCRIPTOR: <------------------------------------------+
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+---------+-------------------+---------------------------------+
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| BYTE | CONTENTS | MEANING |
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+---------+-------------------+---------------------------------+
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| 0-10 | 11 bytes | field name in ASCII zero-filled |
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+---------+-------------------+---------------------------------+
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| 11 | 1 byte | field type in ASCII |
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| | | (C N L D or M) |
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+---------+-------------------+---------------------------------+
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| 12-15 | 32 bit number | field data address |
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| | | (address is set in memory) |
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+---------+-------------------+---------------------------------+
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| 16 | 1 byte | field length in binary |
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+---------+-------------------+---------------------------------+
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| 17 | 1 byte | field decimal count in binary |
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+---------+-------------------+---------------------------------+
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| 18-31 | 14 bytes | reserved bytes (version 1.00) |
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+---------+-------------------+---------------------------------+
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The data records are layed out as follows:
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1. Data records are preceeded by one byte that is a space (20H) if the
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record is not deleted and an asterisk (2AH) if it is deleted.
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2. Data fields are packed into records with no field separators or
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record terminators.
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3. Data types are stored in ASCII format as follows:
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DATA TYPE DATA RECORD STORAGE
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--------- --------------------------------------------
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Character (ASCII characters)
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Numeric - . 0 1 2 3 4 5 6 7 8 9
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Logical ? Y y N n T t F f (? when not initialized)
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Memo (10 digits representing a .DBT block number)
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Date (8 digits in YYYYMMDD format, such as
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19840704 for July 4, 1984)
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