You can use the following formula to return the number of fields in a table file: (x – 296/32). In the formula, x is the position of the first record (bytes 8 to 9 in the table header record), 296 is 263 (backlink info) + 1 (header record terminator) + 32 (first field subrecord), and 32 is the length of a field subrecord.


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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: 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 – 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).

11
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

16
Length of field (in bytes)

17
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


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

Remarks
Visual FoxPro modifies the table header when you turn on or add autoincrementing for field values.

Visual FoxPro does not modify the header of a file that has been saved to a FoxPro 2.x file format unless one of the following features has been added to the file:

Null value support

DateTime, Currency, and Double data types

CHAR or MEMO field is marked as Binary

A table is added to a database (.dbc) file