DBASE FOXBASE PDF
0x02 FoxBASE; 0x03 FoxBASE+/Dbase III plus, no memo; 0x30 Visual FoxPro; 0x31 Visual FoxPro, autoincrement enabled; 0x32 Visual. This file is either (for dBASE) or (for FoxBase). Newer dBASE versions add yet more files for commands, procedures, backups. Some apps never die, but is dBASE still relevant? to ship fixes, and by that time , people had moved on to clones of dBASE like FoxBase.
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dBASE File Format (with coding details): DBF and DBT/FPT file structure | Independent Software
In it, dBASE stores the database description, field descriptors and record data. Ancient dBASE databases may have only a. This file is either a. Newer dBASE versions add yet more files for commands, procedures, backups, reports and indices. These files are not described in this document.
The field descriptors follow directly after the header data, while the header contains an offset to the start of the record data. The first element in any. Some of the bytes contained in the header are reserved and start being used more as the version number increases.
Wikipedia tells us that the version byte is encoded like so:. At most, it appears that the highest bit bit 7 incidates the presence of a memo file. In general, I find it is best to simply test for the presence of an. In general, the version byte can be used to determine if a dBASE file reader offers support for the file being opened.
Number of bytes in the header: In some versions, the record data starts directly after the field descriptor list, and it is not necessary to use this offset.
In others, there is a gap between the field descriptors and the start of the record data, presumably to align foxbsae record data to a round start address, and it is necessary to move the read pointer to this offset. Number of bytes in a record: The size of the records in a. Records are stored one after the other, with no delimiter.
It is therefore necessary to know the record size in order to read the records. A field descriptor for each table field appears directly after the header data. Each field descriptor has a fixed size of 32 bytes.
Some of the foxbaase in the field descriptor are marked as reserved and start to be used in later dBASE versions.
After the last field descriptor, a dbaze descriptor array terminator 0x0d appears. Since the header does not contain a field count, it is important to watch for the terminator while reading field descriptors.
The field name is not a null-terminated string but rather a fixed-size foxbwse array padded with null bytes. Note that duplicate field names may appear in a.
The field data address is used internally by some dBASE versions to map fields to memory.
xbase The address has no meaning in a. The field length is the number of bytes used by foxbwse field in each record. This applies to character strings which are padded with spaces in the recordsbut also to some but not all number field types that are stored as text. Subsequent versions added some new types. They also move away from the string-based storage approach to a more compact binary storage, which is something to be wary of while reading the data.
The field descriptor array is followed by data for each record. Note that foxbxse record data may start directly after the fields, or there may be a gap between the field descriptors and the record data.
For dbsse reason, the header length word from the header must be used to ofxbase the start of the record data. Records are stored one after the other, with no gaps, field separators or record. Records continue until the end of the. Note that in some cases, this marker is not present. Each record is preceded by a deletion marker character. This is either a space 0x20 if the record is not deleted, or an asterisk 0x2a if the record is deleted.
After reading the dhase marker, reading a record is a matter of reading a value of each field that the. All fields values occupy the number of bytes specified in the field length property of their field descriptor. A value of 3. Reading these fields is a matter of converting the text to the appropriate data type. Note that fields may be filled entirely with spaces to indicate an uninitialized value not a NULL value — these had not been invented foxabse.
For a numeric value, for example C:. In later versions, numeric data is encoded as binary values in little-endian byte order.
This is the case for field types I and Yalthough the older numeric types are still encoded as strings. Reading these values involves foxbqse the specified number of bytes from the input stream, then converting them from binary to the appropriate type.
For an integer value, for example C:. DateTime values are encoded as 32 bits numbers. Not all data resides in the. For dBASE, this is the. In the memo file, entries are stored as blocks. Each block has a fixed size, and there is a header structure which specifies the size of each xbase. Note that the dbawe structure itself is considered a block block 0 and generally bytes in size. If the block size is smaller than bytes, the header structure may occupy several blocks. However, no memo index will ever point to data inside the header.
Therefore, the first memo index will foxbasr at least 1, and likely higher than that. The data blocks in the memo file contains the foxbsae for the memos themselves. Each memo can occupy multiple blocks if its data size exceeds the block size. Memo data is string data.
If the memo data does not extend to fpxbase end of the block, the remaining bytes are filled with spaces.
For the memo data type, records in the. An important caveat follows. That is, an index value of 62, in a memo field with field length 10, is stored as 62 preceded by 8 spaces.
In foxbsse versions, the memo voxbase is stored in binary as a bit integer value. Code can distinguish between these two storage approaches by determining the field length. When the field length is 4 bytes, then the memo index is stored as a binary integer value. When the field length is greater than 4 bytes, then the memo index is stored as a string.
Header List of field descriptors List foxhase records The field descriptors follow directly after the header data, while the header contains an offset to the start of the record data.
Header The first element in any. Byte Bits Version 0x02 FoxBase 1. May be set to? Type code Type Sample value Description T DateTime A date and time, stored as a number see below, under record reading I Integer Integer value, stored as a little endian bit value, with the highest bit used to negate numbers Y Currency Type code Type Sample value Description M Memo Index of memo block in accompanying memo file, stored as either a string padded with spaces or a binary uint32 value.