Visual FoxPro System Capacities

Článek
10/23/2006

Some capacities may be limited by available memory.

Category	Feature	Number

Table and Index Files

	Maximum # of records per table file	1 billion
	Maximum size of a table file	2 gigabytes
	Maximum # of characters per record	65,500
	Maximum # of fields per record⁽¹⁾	255
	Maximum # of tables open at one time⁽²⁾	255
	Maximum # of characters per table field	254
	Maximum # of bytes per index key in a non-compact index⁽³⁾	100
	Maximum # of bytes per index key in a compact index⁽³⁾	240
	Maximum # of open index files per table⁽²⁾	unlimited
	Maximum # of open indexes in all work areas⁽²⁾	unlimited
	Maximum # of relations	unlimited
	Maximum length of relational expressions	unlimited

Field Characteristics

	Maximum size of character fields	254
	Maximum size of numeric (and float) fields	20
	Maximum number of characters in field names in a free table	10
	Maximum number of characters in field names in a table contained in a database	128
	Minimum value of an integer	-2,147,483,647
	Maximum value of an integer	2,147,483,647
	Digits of precision in numeric computations Visual FoxPro can handle numbers up to 9007199254740992 (2^53) in exact computations.	16
	64 bits = 8 bytes Largest number = 10 ^ 308 = 2 ^ 1023 -> 10 bits per exponent + 1 for exp sign plus 1 for the number's sign => 12 bits. Leaving 52 bits for the mantissa + 1 for implied normalized bit -> 53 bits LOG10(2^53) = 15.95 decimal digits accuracy.

Variables and Arrays

	Default # of variables	1,024
	Maximum # of variables	65,000
	Maximum # of arrays	65,000
	Maximum # of elements per array	65,000

Program and Procedure Files

	Maximum # of lines in source program files	unlimited
	Maximum size of compiled program modules⁽⁴⁾	64K
	Maximum # of procedures per file	unlimited
	Maximum # of nested DO calls	128
	Maximum # of READ nesting levels	5
	Maximum # of nested structured programming commands	384
	Maximum # of passed parameters	27
	Maximum # of transactions	5

Report Designer Capacities

	Maximum # of objects in a report definition⁽²⁾	unlimited
	Maximum length of a report definition	20 inches
	Maximum # of grouping levels	128
	Maximum length of character report variables	255

Other Capacities

	Maximum # of open windows (all types)⁽²⁾	unlimited
	Maximum # of open Browse windows	255
	Maximum # of characters per character string or memory variable	16,777,184
	Maximum # of characters per command line	8,192
	Maximum # of characters per label control on a report	252
	Maximum # of characters per macro substituted line	8,192
	Maximum # of open files	System limit
	Maximum keystrokes in keyboard macro	1,024
	Maximum fields that can be selected by a SQL SELECT statement	255
	Maximum length of a string literal	255

1. If one or more fields allow null values, the limit is reduced by one to 254 fields.
2. Limited by memory and available file handles. .cdx files use only one file handle.
3. If the collating sequence is set to MACHINE, each character uses one byte. If the collating sequence is not set to MACHINE, each character uses two bytes. If the indexed field supports null values, one additional byte is used in the index key. Note that non-machine indexes are always compact.
4. A program module is one procedure. A program or application can contain an unlimited number of program modules.

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Visual FoxPro System Capacities

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