Data File Header Structure for the dBASE Version 7 Table File
Note: Unless prefaced by "0x", all numbers specified in the Description column of the following tables are decimal. 1.1 Table File HeaderByteContentsDescription
01 byteValid dBASE for Windows table file, bits 0-2 indicate version number: 3 for dBASE Level 5, 4 for dBASE Level 7. Bit 3 and bit 7 indicate presence of a dBASE IV or dBASE for Windows memo file; bits 4-6 indicate the presence of a dBASE IV SQL table; bit 7 indicates the presence of any .DBT memo file (either a dBASE III PLUS type or a dBASE IV or dBASE for Windows memo file).
1-33 bytesDate of last update; in YYMMDD format. Each byte contains the number as a binary. YY is added to a base of 1900 decimal to determine the actual year. Therefore, YY has possible values from 0x00-0xFF, which allows for a range from 1900-2155.
4-732-bit numberNumber of records in the table. (Least significant byte first.)
8-916-bit numberNumber of bytes in the header. (Least significant byte first.)
10-1116-bit numberNumber of bytes in the record. (Least significant byte first.)
12-132 bytesReserved; filled with zeros.
141 byteFlag indicating incomplete dBASE IV transaction.
151 bytedBASE IV encryption flag.
16-2712 bytesReserved for multi-user processing.
281 byteProduction MDX flag; 0x01 if a production .MDX file exists for this table; 0x00 if no .MDX file exists.
291 byteLanguage driver ID.
30-312 bytesReserved; filled with zeros.
32-6332 bytesLanguage driver name.
64-674 bytesReserved.
68-n48 bytes eachField Descriptor Array (see 1.2).
n+11 byte0x0D stored as the Field Descriptor terminator.
n+2See below for
calculations of sizeField Properties Structure
n above is the last byte in the field descriptor array. The size of the array depends on the number of fields in the table file.
1. 2 Field Descriptor Array(One for each field in the table)
ByteContentsDescription
0-3132 bytesField name in ASCII (zero-filled).
321 byteField type in ASCII (B, C, D, N, L, M, @, I, +, F, 0 or G).
331 byteField length in binary.
341 byteField decimal count in binary.
35-362 bytesReserved.
371 byteProduction .MDX field flag; 0x01 if field has an index tag in the production .MDX file; 0x00 if the field is not indexed.
38-392 bytesReserved.
40-434 bytesNext Autoincrement value, if the Field type is Autoincrement, 0x00 otherwise.
44-474 bytesReserved.
1.3 Field Properties StructureThis contains a header describing the Field Properties array, followed by the actual array, followed by property data. It is contained in the .DBF header and comes immediately after the Field Descriptor terminator (See Table 1.1).
ByteContentsDescription
0-116-bit numberNumber of Standard Properties.
2-316-bit numberStart of Standard Property Descriptor Array. (see 1.3.1 )
4-516-bit numberNumber of Custom Properties.
6-716-bit numberStart of Custom Property Descriptor Array. (see 1.3.2 )
8-916-bit numberNumber of Referential Integrity (RI) properties.
10-1116-bit numberStart of RI Property Descriptor Array. (see 1.3.3 )
12-1316-bit numberStart of data - this points past the Descriptor arrays to data used by the arrays - for example Custom property names are stored here.
14-1516-bit numberActual size of structure, including data (Note: in the .DBF this will be padded with zeroes to the nearest 0x200, and may have 0x1A at the end). If the structure contains RI data, it will not be padded.
16-n15 bytes eachStandard Property Descriptor Array (n = (15*number of standard properties) + 16). (see 1.3.1)
(n+1)-m14 bytes eachCustom Property Descriptor Array (m = n+ 14*number of custom properties). (see 1.3.2)
(m+1)-o22 bytes eachRI Property Descriptor Array (o = m+ 22*number of RI properties). (see 1.3.3)
1.3.1 Standard Property and Constraint Descriptor Array
ByteContentsDescription
0-116-bit numberGenerational number. More than one value may exist for a property. The current value is the value with the highest generational number.
2-316-bit numberTable field offset - base one. 01 for the first field in the table, 02 for the second field, etc. Note: this will be 0 in the case of a constraint.
48-bit numberWhich property is described in this record:
01 Required
02 Min
03 Max
04 Default
06 Database constraint
51 byteField Type:
00 No type - constraint
01 Char
02 Numeric
03 Memo
04 Logical
05 Date
06 Float
08 OLE
09 Binary
11 Long
12 Timestamp
13 Double
14 AutoIncrement (not settable from the Inspector)
61 byte0x00 if the array element is a constraint, 0x02 otherwise.
7-104 bytesReserved
11-1216-bit numberOffset from the start of this structure to the data for the property. The Required property has no data associated with it, so it is always 0.
13-1416-bit numberWidth of database field associated with the property, and hence size of the data (includes 0 terminator in the case of a constraint).
1.3.2 Custom Property Descriptor Array
ByteContentsDescription
0-116-bit numberGenerational number. More than one value may exist for a property. The current value is the value with the highest generational number.
2-316-bit numberTable field offset - base one. 01 for the first field in the table, 02 for the second field, etc.
41 byteField Type
01 Char
02 Numeric
03 Memo
04 Logical
05 Date
06 Float
08 OLE
09 Binary
11 Long
12 Timestamp
13 Double
14 AutoIncrement (not settable from the Inspector)
51 byteReserved
6-716-bit numberOffset from the start of this structure to the Custom property name.
8-916-bit numberLength of the Custom property name.
10-1116-bit numberOffset from the start of this structure to the Custom property data.
12-1316-bit numberLength of the Custom property data (does not include null terminator).
1.3.3 Referential Integrity Property Descriptor Array
ByteContentsDescription
08-bit number0x07 if Master (parent), 0x08 if Dependent (child).
1-216-bit numberSequential number, 1 based counting. If this number is 0, this RI rule has been dropped.
3-416-bit numberOffset of the RI rule name - 0 terminated.
5-616-bit numberSize of previous value.
7-816-bit numberOffset of the name of the Foreign Table - 0 terminated.
9-1016-bit numberSize of previous value.
111 byteUpdate & delete behaviour:
Update Cascade 0x10
Delete Cascade 0x01
12-1316-bit numberNumber of fields in the linking key.
14-1516-bit numberOffset of the Local Table tag name - 0 terminated.
16-1716-bit numberSize of previous value.
18-1916-bit numberOffset of the Foreign Table tag name - 0 terminated.
20-2116-bit numberSize of previous value.
(Foreign = in the other table, Local = in this table)
Property DataFor standard properties, everything is stored exactly as it is in the Table records. Custom property data is stored as the Name string, followed immediately by the Value string, and a null terminator. The Constraint text is stored as a null-terminated string.
Table RecordsThe records follow the header in the table file. Data records are preceded by one byte, that is, a space (0x20) if the record is not deleted, an asterisk (0x2A) if the record is deleted. Fields are packed into records without field separators or record terminators. The end of the file is marked by a single byte, with the end-of-file marker, an OEM code page character value of 26 (0x1A).
Storage of dBASE Data TypesExcept for autoincrement fields, all types are initialized to binary zeroes. In addition, any fields which have been assigned a default property will contain the default value.
SymbolData TypeDescription
BBinary, a string10 digits representing a .DBT block number. The number is stored as a string, right justified and padded with blanks.
CCharacterAll OEM code page characters - padded with blanks to the width of the field.
DDate8 bytes - date stored as a string in the format YYYYMMDD.
NNumericNumber stored as a string, right justified, and padded with blanks to the width of the field.
LLogical1 byte - initialized to 0x20 (space) otherwise T or F.
MMemo, a string10 digits (bytes) representing a .DBT block number. The number is stored as a string, right justified and padded with blanks.
@Timestamp8 bytes - two longs, first for date, second for time. The date is the number of days since 01/01/4713 BC. Time is hours * 3600000L + minutes * 60000L + Seconds * 1000L
ILong4 bytes. Leftmost bit used to indicate sign, 0 negative.
+AutoincrementSame as a Long
FFloatNumber stored as a string, right justified, and padded with blanks to the width of the field.
ODouble8 bytes - no conversions, stored as a double.
GOLE10 digits (bytes) representing a .DBT block number. The number is stored as a string, right justified and padded with blanks.
Binary, Memo, OLE Fields and .DBT FilesBinary, memo, and OLE fields store data in .DBT files consisting of blocks numbered sequentially (0, 1, 2, etc.). SET BLOCKSIZE determines the size of each block. The first block in the .DBT file, block 0, is the .DBT file header.
Each binary, memo, or OLE field of each record in the .DBF file contains the number of the block (in OEM code page values) where the field's data actually begins. If a field contains no data, the .DBF file contains blanks (0x20) rather than a number.
When data is changed in a field, the block numbers may also change and the number in the .DBF may be changed to reflect the new location.
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