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  ◄Variables►   ◄Declaring Array Variables►   ◄Contents►   ◄Index►
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Declaring Array Variables
 
An array is a group of objects referenced with the same variable name. The
individual values in an array are elements. Array elements are also
variables, and can be used in any BASIC statement or function that uses
variables. You "dimension" an array when you use it the first time or when
you declare the name, type, and number of elements in the array.
 
Each element in an array is referred to by an array variable subscripted
with an integer or an integer expression. (Noninteger numeric expressions
used as array subscripts are rounded to integer values.) An array-variable
name has as many subscripts as there are dimensions in the array. For
example, V(10) refers to a value in a one-dimensional array, while T$(1,4)
refers to a value in a two-dimensional string array.
 
The default upper subscript value for any array dimension is 10. The
maximum subscript value and the number of dimensions can be set by using
the DIM statement. The maximum number of dimensions for an array is 60.
The maximum number of elements per dimension is 32,767.
 
You may have arrays of any simple variable type, including records. To
declare an array of records, first declare the data type in a TYPE
statement and then dimension the array:
 
  TYPE TreeNode
    LeftPtr AS INTEGER
    RightPtr AS INTEGER
    DataField AS STRING * 20
  END TYPE
  DIM Tree(500) AS TreeNode
 
Each element of the array Tree is a record of type TreeNode. To use a
particular element of a record in an array, use the dot notation form
(variablename.elementname):
 
  CONST MAXEMPLOYEES = 500
  TYPE EmployeeRec
    FullName AS STRING * 25
    SocSec   AS STRING * 9
  END TYPE
  DIM Employees(MAXEMPLOYEES) AS EmployeeRec
  .
  .
  .
  PRINT Employees(I).FullName;" ";Employees(I).SocSec
 
Note: Array names are distinct from simple variable names. The array
      variable T and the simple variable T in the following example
      are two different variables:
 
        DIM T(11)
        T = 2 : T(0) = 1          'T is simple variable.
        FOR I% = 0 TO 10          'T(0) is element of array.
          T(I% + 1) = T * T(I%)
        NEXT
 
Array elements, like simple variables, require a certain amount of memory,
depending on the variable type.
 
To find the total amount of memory required by an array, multiply the
number of elements by the bytes per element required for the array type.
For example, consider the following two arrays:
 
  DIM Array1(0 TO 100) AS INTEGER
  DIM Array#(-5 TO 5)
 
The first array, Array1, has 101 integer elements, so its values take 202
bytes of memory. The second array, Array2, has 11 double-precision
elements, and so its values require 88 bytes of memory.  Because BASIC
must store information about the array along with the array's values,
arrays take slightly more memory than just the space for the values.