Data Type: ARRAY OF

An array is a collection of data elements of the same data type. Single and multi-dimensional arrays of fixed or variable length are supported.

One-dimensional array of fixed length

You can define arrays in the declaration part of a POU or in global variable lists.

Syntax of the declaration of a one-dimensional array:

<variable name> :  ARRAY[ <dimension> ] OF <data type> := <initialization> ;

`<variable name>`	Name of the array Example: `aiCounter`
`<dimension>`	Dimension (lower to higher index limit) Example: `1..100` One dimension can have any number of indexed elements, determined by the lower and upper index limit. The index limits are integers; maximum of the data type `DINT`.
`<data type>`	Data type of an element: Elementary data type User-defined data type Function block Tip References and pointers to `BIT` variables are invalid declarations, as well as array elements with base type `BIT`.
`<initialization>`	Optional Initial values of the array

Example 218. One-dimensional array of 10 integer elements

VAR
    aiCounter : ARRAY[0..9] OF INT;
END_VAR

Lower index limit: 0

Upper index limit: 9

Initialization for the 10 elements:

aiCounter : ARRAY[0..9] OF INT := [0, 10, 20, 30, 40, 50, 60, 70, 80, 90];

Data access

iLocalVariable := aiCounter[2];

The value 20 is assigned to the local variable.

Multi-dimensional array of fixed length

<variable name> :  ARRAY[ <1st dimension> , <next dimensions> ] OF <data type> := <initialization> ;

<variable name> [ <index of 1st dimension> , <index of next dimensions> ]

`<1st dimension>`	First dimension (lower to higher index limit)
`, <next dimensions>`	The next dimensions (comma-separated)

Syntax for data access

`<index of 1st dimension>`	Index limit of the first dimension
`, <next dimensions>`	Index limit of the next dimensions

Example 219. Two-dimensional array

VAR
    aiCardGame : ARRAY[1..2, 3..4] OF INT;
END_VAR

1st dimension: 1 to 2 (2 array elements)

2nd dimension: 3 to 4 (2 array elements)

Initialization for the 2 * 2 elements:

aiCardGame : ARRAY[1..2, 3..4] OF INT := [2(10),2(20)]; // Short notation for [10, 10, 20, 20]

Data access

iLocal_1 := aiCardGame[1, 3]; // Assignment of 10
iLocal_2 := aiCardGame[2, 4]; // Assignment of 20

Example 220. Three-dimensional array

VAR
    aiCardGame : ARRAY[1..2, 3..4, 5..6] OF INT;
END_VAR

1st dimension: 1 to 2

2nd dimension: 3 to 4

3rd dimension: 5 to 6

2 * 2 * 2 = 8 array elements

Initialization

aiCardGame : ARRAY[1..2, 3..4, 5..6] OF INT := [10, 20, 30, 40, 50, 60, 70, 80];

Data access

iLocal_1 := aiCardGame[1, 3, 5]; // Assignment of 10
iLocal_2 := aiCardGame[2, 3, 5]; // Assignment of 20
iLocal_3 := aiCardGame[1, 4, 5]; // Assignment of 30
iLocal_4 := aiCardGame[2, 4, 5]; // Assignment of 40
iLocal_5 := aiCardGame[1, 3, 6]; // Assignment of 50
iLocal_6 := aiCardGame[2, 3, 6]; // Assignment of 60
iLocal_7 := aiCardGame[1, 4, 6]; // Assignment of 70
iLocal_8 := aiCardGame[2, 4, 6]; // Assignment of 80

Initialization

aiCardGame : ARRAY[1..2, 3..4, 5..6] OF INT := [2(10), 2(20), 2(30), 2(40)]; // Short notation for [10, 10, 20, 20, 30, 30, 40, 40]

Data access

iLocal_1 := aiCardGame[1, 3, 5]; // Assignment of 10
iLocal_2 := aiCardGame[2, 3, 5]; // Assignment of 10
iLocal_3 := aiCardGame[1, 4, 5]; // Assignment of 20
iLocal_4 := aiCardGame[2, 4, 5]; // Assignment of 20
iLocal_5 := aiCardGame[1, 3, 6]; // Assignment of 30
iLocal_6 := aiCardGame[2, 3, 6]; // Assignment of 30
iLocal_7 := aiCardGame[1, 4, 6]; // Assignment of 40
iLocal_8 := aiCardGame[2, 4, 6]; // Assignment of 40

Example 221. Three-dimensional array of a user-defined structure

TYPE DATA_A
STRUCT
    iA_1 : INT;
    iA_2 : INT;
    dwA_3 : DWORD;
END_STRUCT
END_TYPE

PROGRAM PLC_PRG
VAR
    aData_A : ARRAY[1..3, 1..3, 1..10] OF DATA_A;
END_VAR

The array aData_A consists of a total of 3 * 3 * 10 = 90 array elements of data type DATA_A.

Initialize partially

aData_A : ARRAY[1..3, 1..3, 1..10] OF DATA_A 
    := [(iA_1 := 1, iA_2 := 10, dwA_3 := 16#00FF),(iA_1 := 2, iA_2 := 20, dwA_3 := 16#FF00),(iA_1 := 3, iA_2 := 30, dwA_3 := 16#FFFF)];

In the example, only the first 3 elements are initialized explicitly. Elements to which no initialization value is assigned explicitly are initialized internally with the default value of the basic data type. This initializes the structure components at 0 starting with the element aData_A[2, 1, 1].

Data access

iLocal_1 := aData_A[1,1,1].iA_1; // Assignment of 1
dwLocal_2 := aData_A[3,1,1].dwA_3; // Assignment of 16#FFFF

Example 222. Array of a function block

FUNCTION BLOCK FBObject_A
VAR
    iCounter : INT;
END_VAR
...
;

PROGRAM PLC_PRG
VAR
    aObject_A : ARRAY[1..4] OF FBObject_A;
END_VAR

The array aObject_A consists of 4 elements. Each element instantiates a FBObject_A function block.

Function call

aObject_A[2]();

Example 223. Two-dimensional array of a function block

Implementation of FB_Something with method FB_Init

FUNCTION_BLOCK FB_Something
VAR
    _nId : INT;
    _lrIn : LREAL;
END_VAR
...
    METHOD FB_Init : BOOL
    VAR_INPUT
        bInitRetains : BOOL;
        bInCopyCode : BOOL;
        nId : INT;
        lrIn : LREAL;
    END_VAR
    _nId := nId;
    _lrIn := lrIN;

The function block FB_Something has a method FB_Init that requires 2 parameters.

Instantiation of the array with initialization

PROGRAM PLC_PRG
VAR
    fb_Something_1 : FB_Something(nId := 11, lrIn := 33.44);
    a_Something : ARRAY[0..1, 0..1] OF FB_Something[(nId := 12, lrIn := 11.22), (nId := 13, lrIn := 22.33), (nId := 14, lrIn := 33.55),(nId := 15, lrIn := 11.22)];
END_VAR

Tip

Note the capability of using the implicit monitoring function CheckBounds() to monitor the maintenance of the index limits at runtime.

Array of arrays

The declaration of an "array of arrays" is an alternative syntax for multidimensional arrays. A collection of elements is nested instead of dimensioning the elements. The nesting depth is unlimited.

Syntax for declaration

<variable name> :  ARRAY[ <any dimension> ] OF ARRAY[ <any dimension> ] OF <data type> := <initialization> ;

Syntax for data access

<variable name> [<index of first array> ] [<index of next array> ]

`<variable name>`	Name of the array Example: `aaaiCounter`
`ARRAY[ <any dimension> ] OF ARRAY[ <any dimension> ] OF ARRAY[ <any dimension> ] OF`	Nested array in three levels Example: `ARRAY[1..2, 1..3] OF ARRAY[1..3] OF ARRAY[1..4] OF ARRAY[1..5]` Note The nesting depth is unlimited.
`<data type>`	Data type of an element: Elementary data type User-defined data type Function block
`<initialization>`	Optional Initial values for the nested array

PROGRAM PLC_PRG
VAR
    aiPoints : ARRAY[1..2,1..3] OF INT := [1,2,3,4,5,6];
    ai2Boxes : ARRAY[1..2] OF ARRAY[1..3] OF INT := [ [1, 2, 3], [ 4, 5, 6]];
    ai3Boxes : ARRAY[1..2] OF ARRAY[1..3] OF ARRAY[1..4] OF INT := [ [ [1, 2, 3, 4], [5, 6, 7, 8 ], [9, 10, 11, 12] ], [ [13, 14, 15, 16], [ 17, 18, 19, 20], [21, 22, 23, 24] ] ];
    ai4Boxes : ARRAY[1..2] OF ARRAY[1..3] OF ARRAY[1..4] OF ARRAY[1..5] OF INT;
END_VAR

aiPoints[1, 2] := 1200;
ai2Boxes[1][2] := 1200;

The variables aiPoints and ai2Boxes collect the same data elements, however the syntax for the declaration differs from that of the data access.

Array of variable length

In function blocks, functions, or methods, you can declare arrays of variable length in the VAR_IN_OUT declaration section.

The LOWER_BOUND and UPPER_BOUND operators are provided for determining the index limits of the actual used array at runtime.

Tip

Only statically declared arrays (not arrays generated by means of the operator __NEW) may be passed to an array with variable length.

Syntax of the declaration of a one-dimensional array of variable length

<variable name> :  ARRAY[*] OF <data type> := <initialization> ;

<variable name>

Name of the array

Example: aMyVariableArray

<data type>

Data type of an element:

Elementary data type
User-defined data type
Function block

<initialization>

Optional

Initial values for the array of arrays

Syntax of the declaration of a multi-dimensional array of variable length

<variable name> :  ARRAY[*, *] OF <data type> := <initialization> ;

<variable name>

Name of the array

Example: aMyVariableArray

ARRAY[*, *]

Declaration for a two-dimensional array of variable length

Formally, an asterisk stands for each dimension of variable length. The dimensions are comma-separated.

Note

Any number of dimensions of variable length are permitted.

Syntax of the operators for calculating the limit index

LOWER_BOUND( <variable name> , <dimension number> )
UPPER_BOUND( <variable name> , <dimension number> )

The SUM function adds the integer values of the array elements and returns the calculated sum as a result. The sum is calculated across all array elements available at runtime. As the actual number of array elements will only be known at runtime, the local variable is declared as a one-dimensional array of variable length.

FUNCTION SUM: INT;
VAR_IN_OUT
    aiData : ARRAY[*] OF INT;
END_VAR
VAR
    diCounter : DINT;
    iResult : INT;
END_VAR

iResult := 0;
FOR diCounter := LOWER_BOUND(aiData, 1) TO UPPER_BOUND(aiData, 1) DO // Calculates the length of the current array
    iResult := iResult + aiData[diCounter];
END_FOR;
SUM := iResult;