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dbf-structure [2016/04/15 07:12]
dbfmanager created
dbf-structure [2016/04/15 10:27] (current)
dbfmanager
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 +====== DBF structure ======
  
 +A table file consists of a header record and data records. The header record defines the structure of the table and contains any other information related to the table. The header record starts at file position zero. Data records follow the header, in consecutive bytes, and contain the actual text of the fields.
 +
 +Note: The data in the data file starts at the position indicated in bytes 8 to 9 of the header record. Data records begin with a delete flag byte. If this byte is an ASCII space (0x20), the record is not deleted. If the first byte is an asterisk (0x2A), the record is deleted. The data from the fields named in the field subrecords follows the delete flag.
 +
 +The length of a record, in bytes, is determined by summing the defined lengths of all fields. Integers in table files are stored with the least significant byte first
 +
 +**Table Header Record Structure**
 +
 +^ Byte offset ​             ^ Description ​                                                     ^
 +| 0                        | File type:\\ 0x02   ​FoxBASE\\ 0x03   ​FoxBASE+/​Dbase III plus, no memo\\ 0x30   ​Visual FoxPro\\ 0x31   ​Visual FoxPro, autoincrement enabled\\ 0x32   ​Visual FoxPro, Varchar, Varbinary, or Blob-enabled\\ 0x43   dBASE IV SQL table files, no memo\\ 0x63   dBASE IV SQL system files, no memo\\ 0x83   ​FoxBASE+/​dBASE III PLUS, with memo\\ 0x8B   dBASE IV with memo\\ 0xCB   dBASE IV SQL table files, with memo\\ 0xF5   ​FoxPro 2.x (or earlier) with memo\\ 0xFB   ​FoxBASE |
 +|1 - 3                     | Last update (YYMMDD) |
 +|4 – 7                     | Number of records in file |
 +|8 – 9                     | Position of first data record |
 +|10 – 11                   | Length of one data record, including delete flag |
 +|12 – 13                   | Reserved |
 +|14                        | Incomplete transaction/​Transaction ended (or rolled back)/​Transaction started |
 +|15                        | Encryption flag |
 +|16 – 27                   | Reserved |
 +|28                        | Table flags:\\ 0x01   file has a structural .cdx\\ 0x02   file has a Memo field\\ 0x04   file is a database (.dbc)\\\\ This byte can contain the sum of any of the above values. For example, the value 0x03 indicates the table has a structural .cdx and a Memo field. |
 +|29                        | Code page mark |
 +|30 – 31                   | Reserved, contains 0x00 |
 +|32                        | Header record terminator (0x0D) |
 +
 +**Field Subrecords Structure**
 +
 +^ Byte offset ​             ^ Description ​                                                     ^
 +| 0 – 10                        | Field name with a maximum of 10 characters. If less than 10, it is padded with null characters (0x00). |
 +|11 | Field type: \\ C   ​– ​  ​Character\\ Y   ​– ​  ​Currency\\ N   ​– ​  ​Numeric\\ F   ​– ​  ​Float\\ D   ​– ​  ​Date\\ T   ​– ​  ​DateTime\\ B   ​– ​  ​Double\\ I   ​– ​  ​Integer\\ L   ​– ​  ​Logical\\ M   – Memo\\ G   – General\\ C   ​– ​  ​Character (binary)\\ M   ​– ​  Memo (binary)\\ P   ​– ​  ​Picture\\ Q   ​– ​  ​Varbinary\\ V   ​– ​  ​Varchar (binary)\\ Note:\\ For each Varchar and Varbinary field, one bit, or "​varlength"​ bit, is allocated in the last system field, which is a hidden field and stores the null status for all fields that can be null. If the Varchar or Varbinary field can be null, the null bit follows the "​varlength"​ bit. If the "​varlength"​ bit is set to 1, the length of the actual field value length is stored in the last byte of the field. Otherwise, if the bit is set to 0, length of the value is equal to the field size. | 
 +|12 – 15| Displacement of field in record |
 +|16| Number of decimal places | 
 +|18| Field flags:\\ 0x01   ​System Column (not visible to user)\\ 0x02   ​Column can store null values\\ 0x04   ​Binary column (for CHAR and MEMO only)\\ 0x06   ​(0x02+0x04) When a field is NULL and binary (Integer, Currency, and Character/​Memo fields)\\ 0x0C   ​Column is autoincrementing |
 +|19 - 22| Value of autoincrement Next value |
 +|23| Value of autoincrement Step value |
 +|24 – 31| Reserved |
dbf-structure.txt · Last modified: 2016/04/15 10:27 by dbfmanager