COBOL DATA-POINTER - Quick Reference

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* Basic DATA-POINTER declaration
01  data-pointer USAGE IS POINTER.
01  another-pointer USAGE IS POINTER.
 
* DATA-POINTER with ADDRESS OF
01  data-item PIC X(50) VALUE "Sample data".
01  pointer-to-data USAGE IS POINTER.
 
* Assigning address to pointer
SET pointer-to-data TO ADDRESS OF data-item.
 
* Accessing data through pointer
01  accessed-data PIC X(50).
MOVE ADDRESS OF accessed-data TO pointer-to-data.
 
* Multiple pointers
01  pointer-array OCCURS 10 TIMES.
    05  array-pointer USAGE IS POINTER.
01  current-pointer USAGE IS POINTER.
 
* Pointer arithmetic (if supported)
SET current-pointer UP BY 4.
SET current-pointer DOWN BY 2.

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* Pointer operations and memory management
PROCEDURE DIVISION.
POINTER-OPERATIONS.
    * Initialize pointer
    SET data-pointer TO NULL.
    
    * Allocate memory and assign to pointer
    PERFORM allocate-memory.
    
    * Use pointer to access data
    PERFORM access-data-through-pointer.
    
    * Free memory when done
    PERFORM free-memory.
    
    STOP RUN.
 
ALLOCATE-MEMORY.
    * Allocate memory for data
    ALLOCATE data-item RETURNING data-pointer.
    
    * Check if allocation was successful
    IF data-pointer = NULL
        DISPLAY "Memory allocation failed"
        PERFORM error-handling
    ELSE
        DISPLAY "Memory allocated successfully"
    END-IF.
 
ACCESS-DATA-THROUGH-POINTER.
    * Access data through pointer
    IF data-pointer NOT = NULL
        * Use pointer to access data
        MOVE "Data accessed through pointer" TO data-item.
        DISPLAY "Data: " data-item
    ELSE
        DISPLAY "Pointer is null"
    END-IF.
 
FREE-MEMORY.
    * Free allocated memory
    IF data-pointer NOT = NULL
        FREE data-pointer
        SET data-pointer TO NULL
        DISPLAY "Memory freed successfully"
    END-IF.

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* Dynamic array management using DATA-POINTER
DATA DIVISION.
WORKING-STORAGE SECTION.
01  dynamic-array.
    05  array-size PIC 9(4) VALUE 0.
    05  array-pointer USAGE IS POINTER.
01  array-element PIC 9(4).
01  index PIC 9(4).
 
PROCEDURE DIVISION.
MANAGE-DYNAMIC-ARRAY.
    * Create dynamic array
    PERFORM create-dynamic-array.
    
    * Populate array
    PERFORM populate-array.
    
    * Process array
    PERFORM process-array.
    
    * Clean up
    PERFORM cleanup-array.
    
    STOP RUN.
 
CREATE-DYNAMIC-ARRAY.
    * Get array size from user
    DISPLAY "Enter array size: ".
    ACCEPT array-size.
    
    * Allocate memory for array
    ALLOCATE array-element(array-size) RETURNING array-pointer.
    
    IF array-pointer = NULL
        DISPLAY "Failed to allocate array memory"
        STOP RUN
    ELSE
        DISPLAY "Array created with size: " array-size
    END-IF.
 
POPULATE-ARRAY.
    * Populate array with values
    PERFORM VARYING index FROM 1 BY 1
        UNTIL index > array-size
        MOVE index TO array-element(index)
        DISPLAY "Element " index ": " array-element(index)
    END-PERFORM.
 
PROCESS-ARRAY.
    * Process array elements
    DISPLAY "Processing array elements...".
    PERFORM VARYING index FROM 1 BY 1
        UNTIL index > array-size
        * Process each element
        COMPUTE array-element(index) = array-element(index) * 2
        DISPLAY "Processed element " index ": " array-element(index)
    END-PERFORM.
 
CLEANUP-ARRAY.
    * Free array memory
    IF array-pointer NOT = NULL
        FREE array-pointer
        SET array-pointer TO NULL
        DISPLAY "Array memory freed"
    END-IF.

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* Linked list implementation using DATA-POINTER
DATA DIVISION.
WORKING-STORAGE SECTION.
01  linked-list-node.
    05  node-data PIC X(50).
    05  next-node USAGE IS POINTER.
01  list-head USAGE IS POINTER.
01  current-node USAGE IS POINTER.
01  new-node USAGE IS POINTER.
01  node-count PIC 9(3) VALUE 0.
 
PROCEDURE DIVISION.
LINKED-LIST-OPERATIONS.
    * Initialize empty list
    SET list-head TO NULL.
    
    * Add nodes to list
    PERFORM add-node-to-list.
    PERFORM add-node-to-list.
    PERFORM add-node-to-list.
    
    * Display list
    PERFORM display-list.
    
    * Clean up list
    PERFORM cleanup-list.
    
    STOP RUN.
 
ADD-NODE-TO-LIST.
    * Create new node
    ALLOCATE linked-list-node RETURNING new-node.
    
    IF new-node = NULL
        DISPLAY "Failed to allocate node memory"
        RETURN
    END-IF.
    
    * Initialize new node
    SET next-node OF new-node TO NULL.
    MOVE "Node data " TO node-data OF new-node.
    ADD 1 TO node-count.
    MOVE node-count TO node-data OF new-node(11:3).
    
    * Add to beginning of list
    SET next-node OF new-node TO list-head.
    SET list-head TO new-node.
    
    DISPLAY "Added node: " node-data OF new-node.
 
DISPLAY-LIST.
    * Display all nodes in list
    DISPLAY "Linked List Contents:".
    SET current-node TO list-head.
    
    PERFORM UNTIL current-node = NULL
        DISPLAY "Node: " node-data OF current-node
        SET current-node TO next-node OF current-node
    END-PERFORM.
 
CLEANUP-LIST.
    * Free all nodes in list
    DISPLAY "Cleaning up linked list...".
    SET current-node TO list-head.
    
    PERFORM UNTIL current-node = NULL
        SET new-node TO next-node OF current-node
        FREE current-node
        SET current-node TO new-node
    END-PERFORM.
    
    SET list-head TO NULL.
    DISPLAY "Linked list cleaned up".