Pointers and references: Difference between revisions

===Pointers===

Pointers are declared like so, optionally with the type or program they will point to:

 

<code>USAGE POINTER</code> data items are used in conjunction with <code>BASED</code> data items, with <code>ALLOCATE</code> optionally giving a pointer the address of the allocated memory. Pointers can also be used to free allocated memory, which will cause the pointer to be set to <code>NULL</code>.

 

<code>USAGE PROGRAM-POINTER</code> data items are used to point to programs and their entry points.

{{works with|OpenCOBOL}}

{{works with|Visual COBOL}}

 

Both types of pointer support basic pointer arithmetic.

SET ptr2 DOWN BY LENGTH OF foo</syntaxhighlight>

 

Pointers can also be set to point to where other pointers are pointing or to other pointers themselves.

SET ptr2 TO ADDRESS OF ptr3 *> ptr2 points to ptr3</syntaxhighlight>

 

To alter the value pointed to by a pointer, the <code>SET</code> statement is needed once again and is used to set the address of <code>BASED</code> or <code>LINKAGE SECTION</code> data items, which can then be used to modify the data.

MOVE "bar" TO foo</syntaxhighlight>

 

===References===

Object references are declared like so, optionally with the class/interface they will reference:

 

They contain either a reference to an object or <code>NULL</code>.

 

They are initialised using by invoking a class constructor, and set using the <code>SET</code> statement.

SET another-obj-ref TO obj-ref</syntaxhighlight>