CONST Statement Details Syntax CONST constantname = expression [,constantname = expression]... Argument Description constantname A name following the same rules as a BASIC variable name. You may add to the name a type-declaration character (%, &, !, #, or \$) to indicate its type, but this character is not part of the name. expression An expression consisting of literals (such as 1.0), other constants, or any of the arithmetic and logical operators except exponentiation (^). You may also use a single literal string such as "Error on input". You cannot use string concatenation, variables, user-defined functions, or intrinsic functions like SIN or CHR\$ in expressions assigned to constants. If you use a type-declaration character in the name, you may omit the character when the name is used, as shown in the following example: CONST MAXDIM% = 250 . . . DIM AccountNames\$(MAXDIM) If you omit the type-declaration character, the constant is given a type based on the expression in the CONST statement. Strings always yield a string constant. With numeric expressions, the expression is evaluated and the constant is given the simplest type that can represent the constant. For example, if the expression gives a result that can be represented as an integer, the constant is given an integer type. Note: Names of constants are not affected by DEFtype statements such as DEFINT. A constant's type is determined either by an explicit type-declaration character or by the type of the expression. Constants must be defined before they are referenced. The following example produces an error because the constant ONE is not defined before it is used to define TWO (constants are defined from left to right): CONST TWO = ONE + ONE, ONE = 1 Constants declared in a SUB or FUNCTION are local to the SUB or FUNCTION. A constant declared outside a procedure is defined throughout the module. You can use constants anywhere that you would use an expression. A common programming practice is to use a statement like the following (recall that any nonzero value represents "true"): TRUE=-1 Constants offer several advantages over using variables for constant values: - Constants need to be defined only once for an entire module. - Constants cannot be inadvertently changed. - In stand-alone programs, using constants produces more efficient code than using variables. - Constants make programs easier to modify.