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REDIM changes the space allocated to an array that has been declared
dynamic.
 
REDIM [SHARED | PRESERVE] variable(subscripts) [AS type]
               [,variable(subscripts) [AS type]]...
    ■ The SHARED attribute differs from the SHARED statement, which affects
      only the variables within a single module. SHARED can be used in REDIM
      statements only in the module-level code.
    ■ PRESERVE preserves data when changing the outer bound of the array.
    ■ subscripts are the dimensions of the array. Multiple
      dimensions can be declared. The subscript syntax is:
 
        [lower TO] upper [,[lower TO] upper]...
 
         lower TO upper    Indicates the lower and upper bounds of an
                           array's subscripts. Lower and upper are numeric
                           expressions that specify the lowest and highest
                           value for the subscript. See the
                           ◄DIM statement details► for more information
                           about using the TO keyword.
 
    ■ AS type declares the type of the variable. The type may be
      INTEGER, LONG, SINGLE, DOUBLE, STRING (for variable-length strings),
      STRING * length (for fixed-length strings), CURRENCY, or a user-
      defined type.
 
New Features
    ■ The PRESERVE keyword preserves data in the array, allowing you
      to allocate space to arrays more efficiently.
    ■ BASIC now supports the CURRENCY data type (type suffix @). This is
      used in the AS type clause of REDIM.
    ■ BASIC now supports static arrays in user-defined types.
 
Usage Notes
    ■ The REDIM statement changes the space allocated to an dynamic array.
    ■ When a REDIM statement is compiled, all arrays declared in the
      statement are treated as dynamic. At run time, when a REDIM
      statement is executed, the array is deallocated (if it is already
      allocated) and then reallocated with the new dimensions. If you
      do not use PRESERVE, old array-element values are lost.
    ■ The PRESERVE keyword allows you to raise or lower the outer
      bound of a dynamic array without erasing data. For example:
 
      REDIM X(10, 10, 10)
      .
      .
      .
      REDIM PRESERVE X(10, 10, 15)
 
      This example keeps any data entered in the array X() and adds
      space for more elements in the third dimension of the array.
      The third dimension of X() is the rightmost bound of the array.
      To change the leftmost bound, you must compile the program with /R.
 
Important
    ■ Although you can change the size of an array's dimensions with
      the REDIM statement, you cannot change the number of dimensions.
      For example, the following statements are legal:
 
        ' $DYNAMIC
        DIM A(50,50)
        ERASE A
        REDIM A(20,15)    ' Array A still has two dimensions.
 
      However, the following statements are not legal, and produce the
      error message: "Wrong number of dimensions":
 
        ' $DYNAMIC
        DIM A(50,50)
        ERASE A
        REDIM A(5,5,5)   ' Changed number of dimensions from
                         ' two to three.