{{QBDLDATE:05-20-2022}}
{{QBDLTIME:23:16:04}}
A {{KW|REDIM}} statement can re-dimension one [[$DYNAMIC|dynamic]](flexible) [[Arrays|array]] or a [[comma]] separated list of arrays.


{{PageSyntax}}
:[[REDIM]] [{{KW|_PRESERVE}}] [{{KW|SHARED}}] ArrayName[''typesuffix''] ({''max_element''|low_element[{{KW|TO}} ''upper_element'', ...]}) [{{KW|AS}} {{KW|TYPE|Type}}]


{{PageDescription}}
* Can change the number of elements in an array (the present array data is lost unless [[_PRESERVE]] is used).
* Dynamic array elements can also be sized or resized by a program user's entry.
* The [[_PRESERVE]] option also allows the ''element'' range values to be moved upward or downward in '''QB64 only!'''
* {{Parameter|Array}} is the name of the array to be dimensioned or re-dimensioned.
* {{Parameter|elements}} is the number of elements the array should hold. Use the optional [[TO]] {{Parameter|elements2}} to set a range.
* '''Always use the same array [[TYPE]] suffix ([[AS]] type) or a new array type with the same name may be created.'''
* REDIM cannot change [[$STATIC]] arrays created with a [[DIM]] statement unless the [[$DYNAMIC]] [[Metacommand]] is used! 
* To create a dynamic array use the [[$DYNAMIC]] metacommand or use [[REDIM]] rather than [[DIM]] when first creating the array.
* Use REDIM [[_PRESERVE]] to change the range or number of array elements without losing the remaining elements. Data may move up or down to accommodate those boundary changes.  
* '''REDIM [[_PRESERVE]] cannot change the number of array dimensions or type!'''
* [[$DYNAMIC|Dynamic]] arrays MUST be [[REDIM]]ensioned if [[ERASE]] or [[CLEAR]] are used to clear the arrays as they no longer exist. 
* When [[AS]] is used to declare the type, use [[AS]] to retain that type or it will change to [[SINGLE]]!
* '''NOTE: Many QBasic keyword variable names CAN be used with a [[STRING]] suffix($) ONLY! You CANNOT use them without the suffix, use a numerical suffix or use [[DIM]], [[REDIM]], [[_DEFINE]], [[BYVAL]] or [[TYPE]] variable [[AS]] statements!'''
* '''Warning! Do not use negative array upper bound index values as OS access or "Out of Memory" [[ERROR Codes|errors]] will occur!'''


''Example 1:'' The [[$DYNAMIC]] Metacommand allows an array to be re-sized using [[DIM]] and REDIM.
{{CodeStart}}
'{{Cl|$DYNAMIC}}

{{Cl|INPUT}} "Enter array size: ", size 
{{Cl|DIM}} Array(size)

{{Cl|REDIM}} Array(2 * size)

{{Cl|PRINT}} {{Cl|UBOUND}}(Array) 
{{CodeEnd}}


''Example 2:'' Shows the difference between REDIM and REDIM [[_PRESERVE]].
{{CodeStart}}
{{Cl|REDIM}} array(20)
array(10) = 24

{{Cl|PRINT}} array(10)

{{Cl|REDIM}} {{Cl|_PRESERVE}} array(30)
{{Cl|PRINT}} array(10)

{{Cl|REDIM}} array(15)
{{Cl|PRINT}} array(10) 
{{CodeEnd}}
{{OutputStart}}
 24
 24
 0
{{OutputEnd}}
: ''Explanation:'' REDIM without _PRESERVE erases the array data and cannot change the number of dimensions.


{{PageSeeAlso}}
* [[Arrays]] 
* [[DIM]], [[SHARED]]
* [[_PRESERVE]], [[ERASE]]
* [[$DYNAMIC]], [[$STATIC]]


{{PageNavigation}}