Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

  ◄Summary►  ◄Details►  ◄Example►                ◄Contents►  ◄Index►  ◄Back►
──────────────────────────────────────────────────────────────────────────────
 CONST constantname = expression [,constantname = expression]...
 
 Usage Notes
   ■ If you use a type-declaration character in the name, you can 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.
 
   ■ Names of constants are not affected by DEFtype statements such as
     DEFINT. A constant type is determined either by an explicit type-
     declaration character or by the type of the expression.
     See: ◄DEFtype Statements►
 
   ■ Constants must be defined before they are referred to. 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 procedure 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 such as the
     following (any nonzero value represents "true"):
 
         TRUE = -1
 
   ■ Using constants offers several advantages over using variables for
     constant values:
     • You only define constants once for an entire module
     • Constants cannot be inadvertently changed
     • Using constants rather than variables produces faster and often more
       compact code in stand-alone programs
     • Constants make programs easier to modify