Table File Structure (.dbc, .dbf, .frx, .lbx, .mnx, .pjx, .scx, .vcx)

Visual FoxPro 9.0 SP2

See Also

Visual FoxPro uses tables to store data that defines different file types. The following list includes the file types that are saved as tables:

Database (.dbc)
Form (.scx)
Label (.lbx)
Menu (.mnx)
Project (.pjx)
Report (.frx)
Table (.dbf)
Visual class library (.vcx)

You can use and browse these files in the same way that you browse any table file because these files are actually tables.

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.

For information about the table structures of the different file types, see Table Structures of Table Files.

Table Header Record Structure

Byte offset	Description
0	File type: 0x02 FoxBASE / dBase II 0x03 FoxBASE+ / FoxPro /dBase III PLUS / dBase IV, 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 – 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 – n	Field subrecords The number of fields determines the number of field subrecords. One field subrecord exists for each field in the table.
n+1	Header record terminator (0x0D)
n+2 to n+264	A 263-byte range that contains the backlink, which is the relative path of an associated database (.dbc) file, information. If the first byte is 0x00, the file is not associated with a database. Therefore, database files always contain 0x00.

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).

Field type:

W - Blob

C – Character

C – Character (binary)

Y – Currency

B – Double

D – Date

T – DateTime

F – Float

G – General

I – Integer

L – Logical

M – Memo

M – Memo (binary)

N – Numeric

P – Picture

Q - Varbinary

V - Varchar

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

Length of field (in bytes)

Number of decimal places

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

Value of autoincrement Step value

24 – 31

Reserved

For information about limitations on characters per record, maximum fields, and so on, see Visual FoxPro System Capacities.

Table File Structure (.dbc, .dbf, .frx, .lbx, .mnx, .pjx, .scx, .vcx)

Table Header Record Structure

Field Subrecords Structure

Remarks

See Also

Tasks

Reference

Other Resources