Basics of Structure Triple Pointers
=====================================

In this section, you are going to learn

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                How to use Triple Pointers ?

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                Basics of Triple Pointers

                * :ref:`1 Triple Pointer 1 Double Pointer, 1 Single Pointer : Simple variables <basic_ptr_struct_tp_sp_ex1>`
                * :ref:`1 Triple Pointer, 1 Double Pointer, 1 Single Pointer : With Single pointer pointing to arrays <basic_ptr_struct_tp_sp_ex2>`
                * :ref:`1 Triple Pointer, 1 Double Pointer, 1 Single Pointer : With Single pointer heap allocation <basic_ptr_struct_tp_sp_ex3>`
                * :ref:`1 Triple Pointer, 1 Double Pointer : With two heap allocations : Create 1x1 array <basic_ptr_struct_tp_sp_ex4>`
                * :ref:`1 Triple Pointer, 1 Double Pointer : With two heap allocations : Create 1x10 array <basic_ptr_struct_tp_sp_ex5>`
                * :ref:`1 Triple Pointer, 1 Double Pointer : Pointing to array of single pointers : Dynamic <basic_ptr_struct_tp_sp_ex7>`

.. _basic_ptr_struct_tp_sp_ex1:

.. tab-set::

        .. tab-item:: 1 Triple Pointer, 1 Double Pointer, 1 Single Pointer : Simple variables

                * Step 1 : Define a Structure

                .. code-block:: c

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        struct ABC x = { .a = 1, .b = 2, .c = 3 };

                * Step 2 : Define a Single pointer

                .. code-block:: c

                        struct ABC *sp = &x;

                OR

                .. code-block:: c

                        struct ABC *sp;

                        sp = &x;

                * Step 3 : Define a Double pointer

                .. code-block:: c

                        struct ABC **dp = &sp;

                OR

                .. code-block:: c

                        struct ABC **dp;

                        dp = &sp;

                * Step 4 : Define a Triple pointer

                .. code-block:: c

                        struct ABC ***tp = &dp;

                OR

                .. code-block:: c

                        struct ABC ***tp;

                        tp = &dp;

                * Step 5 : Access user data (in this case structure) using single pointer

                .. code-block:: c

                        printf("sp->a = %d\n", sp->a);
                        printf("sp->b = %d\n", sp->b);
                        printf("sp->c = %d\n", sp->c);

                * Step 6 : Access user data (in this case structure) using double pointer

                .. code-block:: c

                        printf("(*dp)->a = %d\n", (*dp)->a);
                        printf("(*dp)->b = %d\n", (*dp)->b);
                        printf("(*dp)->c = %d\n", (*dp)->c);

                * Step 7 : Access user data (in this case structure) using triple pointer

                .. code-block:: c

                        printf("(**tp)->a = %d\n", (**tp)->a);
                        printf("(**tp)->b = %d\n", (**tp)->b);
                        printf("(**tp)->c = %d\n", (**tp)->c);

                * See full program below

                .. code-block:: c

                        #include <stdio.h>

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        int main(void)
                        {
                                struct ABC x = { .a = 1, .b = 2, .c = 3 };

                                struct ABC *sp;
                                sp = &x;

                                struct ABC **dp;
                                dp = &sp;

                                struct ABC ***tp;
                                tp = &dp;

                                printf("sp->a = %d\n", sp->a);
                                printf("sp->b = %d\n", sp->b);
                                printf("sp->c = %d\n", sp->c);

                                printf("(*dp)->a = %d\n", (*dp)->a);
                                printf("(*dp)->b = %d\n", (*dp)->b);
                                printf("(*dp)->c = %d\n", (*dp)->c);

                                printf("(**tp)->a = %d\n", (**tp)->a);
                                printf("(**tp)->b = %d\n", (**tp)->b);
                                printf("(**tp)->c = %d\n", (**tp)->c);

                                return 0;
                        }

                * Output is as below

                .. code-block:: c

                        sp->a = 1
                        sp->b = 2
                        sp->c = 3

                        (*dp)->a = 1
                        (*dp)->b = 2
                        (*dp)->c = 3

                        (**tp)->a = 1
                        (**tp)->b = 2
                        (**tp)->c = 3

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                        Summary of Naming conventions

                        Consider

                        .. code-block:: c

                                struct ABC ***tp;

                        then

                        * tp is a triple pointer
                        * \*tp is a double pointer
                        * \*\*tp is a single pointer
                        * \*\*\*tp is user data

.. _basic_ptr_struct_tp_sp_ex2:

.. tab-set::

        .. tab-item:: 1 Triple Pointer, 1 Double Pointer, 1 Single Pointer : With Single pointer pointing to arrays

                * Step 1 : Define a single dimension array of structures

                .. code-block:: c

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        struct ABC arr[3] = {
                                { .a = 1, .b = 2, .c = 3 },
                                { .a = 10, .b = 20, .c = 30 },
                                { .a = 100, .b = 200, .c = 300 },
                        };

                * Step 2 : Define a single pointer

                .. code-block:: c

                        struct ABC *sp = arr;

                OR

                .. code-block:: c

                        struct ABC *sp;

                        sp = arr;

                OR

                .. code-block:: c

                        struct ABC *sp;

                        sp = &arr[0];

                * Step 3 : Define a double pointer

                .. code-block:: c

                        struct ABC **dp = &sp;

                OR

                .. code-block:: c

                        struct ABC **dp;

                        dp = &sp;

                * Step 4 : Define a Triple pointer

                .. code-block:: c

                        struct ABC ***tp = &dp;

                OR

                .. code-block:: c

                        struct ABC ***tp;

                        tp = &dp;

                * Step 5 : Access user data (in this case array of structures) using single pointer variable ``arr``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("arr[%d].a = %d\n", i, arr[i].a);
                                printf("arr[%d].b = %d\n", i, arr[i].b);
                                printf("arr[%d].c = %d\n", i, arr[i].c);
                        }

                * Step 5 : Access user data (in this case array of structures) using single pointer variable ``sp``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("sp[%d].a = %d\n", i, sp[i].a);
                                printf("sp[%d].b = %d\n", i, sp[i].b);
                                printf("sp[%d].c = %d\n", i, sp[i].c);
                        }


                * Step 6 : Access user data (in this case array of structures) using double pointer variable ``dp``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("(*dp)[%d].a = %d\n", i, (*dp)[i].a);
                                printf("(*dp)[%d].b = %d\n", i, (*dp)[i].b);
                                printf("(*dp)[%d].c = %d\n", i, (*dp)[i].c);
                        }

                * Step 7 : Access user data (in this case array of structures) using triple pointer variable ``tp``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("(**tp)[%d].a = %d\n", i, (**tp)[i].a);
                                printf("(**tp)[%d].b = %d\n", i, (**tp)[i].b);
                                printf("(**tp)[%d].c = %d\n", i, (**tp)[i].c);
                        }

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                        Note ``*dp`` should be called as single pointer because of below equations

                        * dp = &sp;
                        * \*dp = sp;

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                        Note ``**tp`` should be called as single pointer because of below equations

                        * tp = &dp;
                        * \*tp = dp;
                        * \*tp = &sp;
                        * \*\*tp = sp;  

                * See full program below

                .. code-block:: c

                        #include <stdio.h>

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        int main(void)
                        {
                                struct ABC arr[3] = {
                                        { .a = 1, .b = 2, .c = 3 },
                                        { .a = 10, .b = 20, .c = 30 },
                                        { .a = 100, .b = 200, .c = 300 },
                                };

                                struct ABC *sp;
                                sp = arr;

                                struct ABC **dp;
                                dp = &sp;

                                struct ABC ***tp;
                                tp = &dp;

                                for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                                {
                                printf("arr[%d].a = %d\n", i, arr[i].a);
                                printf("arr[%d].b = %d\n", i, arr[i].b);
                                printf("arr[%d].c = %d\n", i, arr[i].c);
                                }

                                for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                                {
                                printf("sp[%d].a = %d\n", i, sp[i].a);
                                printf("sp[%d].b = %d\n", i, sp[i].b);
                                printf("sp[%d].c = %d\n", i, sp[i].c);
                                }

                                for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                                {
                                        printf("(*dp)[%d].a = %d\n", i, (*dp)[i].a);
                                        printf("(*dp)[%d].b = %d\n", i, (*dp)[i].b);
                                        printf("(*dp)[%d].c = %d\n", i, (*dp)[i].c);
                                }

                                for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                                {
                                        printf("(**tp)[%d].a = %d\n", i, (**tp)[i].a);
                                        printf("(**tp)[%d].b = %d\n", i, (**tp)[i].b);
                                        printf("(**tp)[%d].c = %d\n", i, (**tp)[i].c);
                                }
        
                                return 0;
                        }

                * Output is as below

                .. code-block:: c

                        arr[0].a = 1
                        arr[0].b = 2
                        arr[0].c = 3
                        arr[1].a = 10
                        arr[1].b = 20
                        arr[1].c = 30
                        arr[2].a = 100
                        arr[2].b = 200
                        arr[2].c = 300

                        sp[0].a = 1
                        sp[0].b = 2
                        sp[0].c = 3
                        sp[1].a = 10
                        sp[1].b = 20
                        sp[1].c = 30
                        sp[2].a = 100
                        sp[2].b = 200
                        sp[2].c = 300

                        (*dp)[0].a = 1
                        (*dp)[0].b = 2
                        (*dp)[0].c = 3
                        (*dp)[1].a = 10
                        (*dp)[1].b = 20
                        (*dp)[1].c = 30
                        (*dp)[2].a = 100
                        (*dp)[2].b = 200
                        (*dp)[2].c = 300

                        (**tp)[0].a = 1
                        (**tp)[0].b = 2
                        (**tp)[0].c = 3
                        (**tp)[1].a = 10
                        (**tp)[1].b = 20
                        (**tp)[1].c = 30
                        (**tp)[2].a = 100
                        (**tp)[2].b = 200
                        (**tp)[2].c = 300

.. _basic_ptr_struct_tp_sp_ex3:

.. tab-set::

        .. tab-item:: 1 Triple Pointer, 1 Double Pointer, 1 Single Pointer : With Single pointer heap allocation

                * Step 1 : Define a single pointer

                .. code-block:: c

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        struct ABC *sp;

                * Step 2 : Allocate heap memory to single pointer

                .. code-block:: c

                        sp = malloc(3 * sizeof(struct ABC));

                * Step 3 : Copy User data to heap memory

                .. code-block:: c

                        sp[0].a = 1;
                        sp[0].b = 2;
                        sp[0].c = 3;

                        sp[1].a = 10;
                        sp[1].b = 20;
                        sp[1].c = 30;

                        sp[2].a = 100;
                        sp[2].b = 200;
                        sp[2].c = 300;

                * Step 4 : Define a double pointer

                .. code-block:: c

                        struct ABC **dp;
                        dp = &sp;

                * Step 5 : Define a Triple pointer

                .. code-block:: c

                        struct ABC ***tp = &dp;

                OR

                .. code-block:: c

                        struct ABC ***tp;

                        tp = &dp;

                * Step 6 : Access User data using single pointer variable ``sp``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("sp[%d].a = %d\n", i, sp[i].a);
                                printf("sp[%d].b = %d\n", i, sp[i].b);
                                printf("sp[%d].c = %d\n", i, sp[i].c);
                        }

                * Step 7 : Access User data using double pointer variable ``dp``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("(*dp)[%d].a = %d\n", i, (*dp)[i].a);
                                printf("(*dp)[%d].b = %d\n", i, (*dp)[i].b);
                                printf("(*dp)[%d].c = %d\n", i, (*dp)[i].c);
                        }

                * Step 8 : Access User data using triple pointer variable ``tp``

                .. code-block:: c

                        for (int i = 0 ; i < sizeof(arr)/sizeof(arr[0]); i++)
                        {
                                printf("(**tp)[%d].a = %d\n", i, (**tp)[i].a);
                                printf("(**tp)[%d].b = %d\n", i, (**tp)[i].b);
                                printf("(**tp)[%d].c = %d\n", i, (**tp)[i].c);
                        }

                * Step 9 : Free memory after usage

                .. code-block:: c

                        free(sp);

                OR

                .. code-block:: c

                        free(*dp);

                OR

                .. code-block:: c

                        free(**tp);

                * See full program below

                .. code-block:: c

                        #include <stdio.h>
                        #include <stdlib.h>
                        #include <string.h>

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        int main(void)
                        {
                                struct ABC *sp;

                                sp = malloc(3 * sizeof(struct ABC));

                                sp[0].a = 1;
                                sp[0].b = 2;
                                sp[0].c = 3;

                                sp[1].a = 10;
                                sp[1].b = 20;
                                sp[1].c = 30;

                                sp[2].a = 100;
                                sp[2].b = 200;
                                sp[2].c = 300;

                                struct ABC **dp;
                                dp = &sp;

                                struct ABC ***tp;
                                tp = &dp;

                                for (int i = 0 ; i < 3; i++)
                                {
                                        printf("sp[%d].a = %d\n", i, sp[i].a);
                                        printf("sp[%d].b = %d\n", i, sp[i].b);
                                        printf("sp[%d].c = %d\n", i, sp[i].c);
                                }
        
                                for (int i = 0 ; i < 3; i++)
                                {
                                        printf("(*dp)[%d].a = %d\n", i, (*dp)[i].a);
                                        printf("(*dp)[%d].b = %d\n", i, (*dp)[i].b);
                                        printf("(*dp)[%d].c = %d\n", i, (*dp)[i].c);
                                }

                                for (int i = 0 ; i < 3; i++)
                                {
                                        printf("(**tp)[%d].a = %d\n", i, (**tp)[i].a);
                                        printf("(**tp)[%d].b = %d\n", i, (**tp)[i].b);
                                        printf("(**tp)[%d].c = %d\n", i, (**tp)[i].c);
                                }

                                free(sp);

                                return 0;
                        }

                * Output is as below

                .. code-block:: c

                        sp[0].a = 1
                        sp[0].b = 2
                        sp[0].c = 3
                        sp[1].a = 10
                        sp[1].b = 20
                        sp[1].c = 30
                        sp[2].a = 100
                        sp[2].b = 200
                        sp[2].c = 300

                        (*dp)[0].a = 1
                        (*dp)[0].b = 2
                        (*dp)[0].c = 3
                        (*dp)[1].a = 10
                        (*dp)[1].b = 20
                        (*dp)[1].c = 30
                        (*dp)[2].a = 100
                        (*dp)[2].b = 200
                        (*dp)[2].c = 300

                        (**tp)[0].a = 1
                        (**tp)[0].b = 2
                        (**tp)[0].c = 3
                        (**tp)[1].a = 10
                        (**tp)[1].b = 20
                        (**tp)[1].c = 30
                        (**tp)[2].a = 100
                        (**tp)[2].b = 200
                        (**tp)[2].c = 300

.. _basic_ptr_struct_tp_sp_ex4:

.. tab-set::

        .. tab-item:: 1 Triple Pointer, 1 Double Pointer : With two heap allocations : Create 1x1 array

                * Step 1 : Define a double pointer

                .. code-block:: c

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        struct ABC **dp;

                * Step 2 : Allocate memory to a double pointer

                .. code-block:: c

                        dp = malloc(sizeof(struct ABC *));

                * Step 3 : Allocate memory to a single pointer

                .. code-block:: c

                        *dp = malloc(sizeof(struct ABC));

                * Step 4 : Store user data

                .. code-block:: c

                        (*dp)->a = 1;
                        (*dp)->b = 2;
                        (*dp)->c = 3;

                * Step 5 : Define a Triple pointer

                .. code-block:: c

                        struct ABC ***tp = &dp;

                OR

                .. code-block:: c

                        struct ABC ***tp;

                        tp = &dp;

                * Step 6 : Read user data using ``dp``

                .. code-block:: c

                        printf("(*dp)->a = %d\n", (*dp)->a);
                        printf("(*dp)->b = %d\n", (*dp)->b);
                        printf("(*dp)->c = %d\n", (*dp)->c);

                * Step 7 : Read user data using ``tp``

                .. code-block:: c

                        printf("(**tp)->a = %d\n", (**tp)->a);
                        printf("(**tp)->b = %d\n", (**tp)->b);
                        printf("(**tp)->c = %d\n", (**tp)->c);

                * Step 8 : Free memory in opposite flow of allocation

                .. code-block:: c

                        free(*dp);

                        free(dp);

                OR

                .. code-block:: c

                        free(**tp);

                        free(*tp);

                * See full program below

                .. code-block:: c

                        #include <stdio.h>
                        #include <string.h>
                        #include <stdlib.h>

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        int main(void)
                        {
                                struct ABC **dp;

                                dp = malloc(sizeof(struct ABC *));

                                *dp = malloc(sizeof(struct ABC));

                                (*dp)->a = 1;
                                (*dp)->b = 2;
                                (*dp)->c = 3;

                                printf("(*dp)->a = %d\n", (*dp)->a);
                                printf("(*dp)->b = %d\n", (*dp)->b);
                                printf("(*dp)->c = %d\n", (*dp)->c);

                                struct ABC ***tp;
                                tp = &dp;
        
                                printf("(**tp)->a = %d\n", (**tp)->a);
                                printf("(**tp)->b = %d\n", (**tp)->b);
                                printf("(**tp)->c = %d\n", (**tp)->c);

                                free(*dp); // or free(**tp);

                                free(dp);  // or free(*tp);

                                return 0;
                        }

                * Output is as below

                .. code-block:: c

                        (*dp)->a = 1
                        (*dp)->b = 2
                        (*dp)->c = 3

                        (**tp)->a = 1
                        (**tp)->b = 2
                        (**tp)->c = 3

.. _basic_ptr_struct_tp_sp_ex5:

.. tab-set::

        .. tab-item:: 1 Triple Pointer, 1 Double Pointer : With two heap allocations : Create 1x3 array

                * Step 1 : Define a double pointer

                .. code-block:: c

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        struct ABC **dp;

                * Step 2 : Allocate memory to a double pointer

                .. code-block:: c

                        dp = malloc(sizeof(struct ABC *));

                * Step 3 : Allocate memory to a single pointer

                .. code-block:: c

                        *dp = malloc(3 * sizeof(struct ABC));

                * Step 4 : Copy User data to heap

                .. code-block:: c

                        (*dp)[0].a = 1;
                        (*dp)[0].b = 2;
                        (*dp)[0].c = 3;

                        (*dp)[1].a = 10;
                        (*dp)[1].b = 20;
                        (*dp)[1].c = 30;

                        (*dp)[2].a = 100;
                        (*dp)[2].b = 200;
                        (*dp)[2].c = 300;

                * Step 5 : Define a Triple pointer

                .. code-block:: c

                        struct ABC ***tp = &dp;

                OR

                .. code-block:: c

                        struct ABC ***tp;

                        tp = &dp;

                * Step 6 : Read user data from heap using ``dp``

                .. code-block:: c

                        for (int i = 0; i < 3; i++) {
                                printf("(*dp)[%d].a = %d\n", i, (*dp)[i].a );
                                printf("(*dp)[%d].b = %d\n", i, (*dp)[i].b );
                                printf("(*dp)[%d].c = %d\n", i, (*dp)[i].c );
                        }

                * Step 7 : Read user data from heap using ``tp``

                .. code-block:: c

                        for (int i = 0; i < 3; i++) {
                                printf("(**tp)[%d].a = %d\n", i, (**tp)[i].a );
                                printf("(**tp)[%d].b = %d\n", i, (**tp)[i].b );
                                printf("(**tp)[%d].c = %d\n", i, (**tp)[i].c );
                        }

                * Step 6 : Free memory in opposite flow of allocation

                .. code-block:: c

                        free(*dp);

                        free(dp);

                OR

                .. code-block:: c

                        free(**tp);

                        free(*tp);

                * See full program below

                .. code-block:: c
        
                        #include <stdio.h>
                        #include <string.h>
                        #include <stdlib.h>

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        int main(void)
                        {
                                struct ABC **dp;

                                dp = malloc(sizeof(struct ABC *));
                
                                *dp = malloc(3 * sizeof(struct ABC));

                                (*dp)[0].a = 1;
                                (*dp)[0].b = 2;
                                (*dp)[0].c = 3;

                                (*dp)[1].a = 10;
                                (*dp)[1].b = 20;
                                (*dp)[1].c = 30;

                                (*dp)[2].a = 100;
                                (*dp)[2].b = 200;
                                (*dp)[2].c = 300;

                                struct ABC ***tp;

                                tp = &dp;

                                for (int i = 0; i < 3; i++) {
                                        printf("(*dp)[%d].a = %d\n", i, (*dp)[i].a );
                                        printf("(*dp)[%d].b = %d\n", i, (*dp)[i].b );
                                        printf("(*dp)[%d].c = %d\n", i, (*dp)[i].c );
                                }

                                for (int i = 0; i < 3; i++) {
                                        printf("(**tp)[%d].a = %d\n", i, (**tp)[i].a );
                                        printf("(**tp)[%d].b = %d\n", i, (**tp)[i].b );
                                        printf("(**tp)[%d].c = %d\n", i, (**tp)[i].c );
                                }

                                free(*dp); // or free(**tp);

                                free(dp);  // or free(*tp);

                                return 0;
                        }

                * Output is as below

                .. code-block:: c

                        (*dp)[0].a = 1
                        (*dp)[0].b = 2
                        (*dp)[0].c = 3
                        (*dp)[1].a = 10
                        (*dp)[1].b = 20
                        (*dp)[1].c = 30
                        (*dp)[2].a = 100
                        (*dp)[2].b = 200
                        (*dp)[2].c = 300

                        (**tp)[0].a = 1
                        (**tp)[0].b = 2
                        (**tp)[0].c = 3
                        (**tp)[1].a = 10
                        (**tp)[1].b = 20
                        (**tp)[1].c = 30
                        (**tp)[2].a = 100
                        (**tp)[2].b = 200
                        (**tp)[2].c = 300

.. _basic_ptr_struct_tp_sp_ex7:

.. tab-set::

        .. tab-item:: 1 Triple Pointer, 1 Double Pointer : Pointing to array of single pointers : Dynamic

                * Step 1 : Define a double pointer

                .. code-block:: c

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        struct ABC **dp;

                * Step 2 : Allocate heap memory : Create 2 single pointers ``dp[0]``, ``dp[1]``

                .. code-block:: c

                        dp = malloc(2 * sizeof(struct ABC *));

                * Step 3 : Allocate heap memory : Create 2 single dimension structure arrays of size 3 structures each

                .. code-block:: c

                        dp[0] = malloc(3 * sizeof(struct ABC));
                        dp[1] = malloc(3 * sizeof(struct ABC));

                * Step 4 : Store user data

                .. code-block:: c

                        dp[0][0].a = 1;
                        dp[0][0].b = 2;
                        dp[0][0].c = 3;

                        dp[0][1].a = 4;
                        dp[0][1].b = 5;
                        dp[0][1].c = 6;

                        dp[0][2].a = 7;
                        dp[0][2].b = 8;
                        dp[0][2].c = 9;

                        dp[1][0].a = 10;
                        dp[1][0].b = 11;
                        dp[1][0].c = 12;
                        
                        dp[1][1].a = 13;
                        dp[1][1].b = 14;
                        dp[1][1].c = 15;

                        dp[1][2].a = 16;
                        dp[1][2].b = 17;
                        dp[1][2].c = 18;

                * Step 5 : Define a Triple pointer

                .. code-block:: c

                        struct ABC ***tp = &dp;

                OR

                .. code-block:: c

                        struct ABC ***tp;

                        tp = &dp;

                * Step 6 : Access user data using ``dp``

                .. code-block:: c

                        for (int i = 0 ; i < 2; i++)
                        {
                                for (int j = 0; j < 3; j++)
                                {
                                        printf("dp[%d][%d].a = %d\n", i, j, dp[i][j].a );
                                        printf("dp[%d][%d].b = %d\n", i, j, dp[i][j].b );
                                        printf("dp[%d][%d].c = %d\n", i, j, dp[i][j].c );
                                }
                        }

                * Step 7 : Access user data using ``tp``

                .. code-block:: c

                        for (int i = 0 ; i < 2; i++)
                        {
                                for (int j = 0; j < 3; j++)
                                {
                                        printf("(*tp)[%d][%d].a = %d\n", i, j, (*tp)[i][j].a );
                                        printf("(*tp)[%d][%d].b = %d\n", i, j, (*tp)[i][j].b );
                                        printf("(*tp)[%d][%d].c = %d\n", i, j, (*tp)[i][j].c );
                                }
                        }

                * Step 6 : Free 2 structure arrays

                .. code-block:: c

                        free(dp[0]);
                        free(dp[1]);

                OR                        

                .. code-block:: c

                        free((*tp)[0]);
                        free((*tp)[1]);

                * Step 7 : Free 2 single pointers

                .. code-block:: c

                        free(dp);

                * See full program below

                .. code-block:: c

                        #include <stdio.h>
                        #include <stdlib.h>
                        #include <string.h>

                        struct ABC {
                                int a;
                                int b;
                                int c;
                        };

                        int main(void)
                        {
                                struct ABC **dp;

                                dp = malloc(2 * sizeof(struct ABC *));

                                dp[0] = malloc(3 * sizeof(struct ABC));
                                dp[1] = malloc(3 * sizeof(struct ABC));

                                dp[0][0].a = 1;
                                dp[0][0].b = 2;
                                dp[0][0].c = 3;

                                dp[0][1].a = 4;
                                dp[0][1].b = 5;
                                dp[0][1].c = 6;
       
                                dp[0][2].a = 7;
                                dp[0][2].b = 8;
                                dp[0][2].c = 9;

                                dp[1][0].a = 10;
                                dp[1][0].b = 11;
                                dp[1][0].c = 12;

                                dp[1][1].a = 13;
                                dp[1][1].b = 14;
                                dp[1][1].c = 15;

                                dp[1][2].a = 16;
                                dp[1][2].b = 17;
                                dp[1][2].c = 18;

                                struct ABC ***tp;

                                tp = &dp;

                                for (int i = 0 ; i < 2; i++)
                                {
                                        for (int j = 0; j < 3; j++)
                                        {
                                                printf("dp[%d][%d].a = %d\n", i, j, dp[i][j].a );
                                                printf("dp[%d][%d].b = %d\n", i, j, dp[i][j].b );
                                                printf("dp[%d][%d].c = %d\n", i, j, dp[i][j].c );
                                        }
                                }
        
                                for (int i = 0 ; i < 2; i++)
                                {
                                        for (int j = 0; j < 3; j++)
                                        {
                                                printf("(*tp)[%d][%d].a = %d\n", i, j, (*tp)[i][j].a );
                                                printf("(*tp)[%d][%d].b = %d\n", i, j, (*tp)[i][j].b );
                                                printf("(*tp)[%d][%d].c = %d\n", i, j, (*tp)[i][j].c );
                                        }
                                }
        
                                free(dp[0]);
                                free(dp[1]);

                                free(dp);

                                return 0;
                        }

                * Output as is below

                .. code-block:: c

                        dp[0][0].a = 1
                        dp[0][0].b = 2
                        dp[0][0].c = 3
                        dp[0][1].a = 4
                        dp[0][1].b = 5
                        dp[0][1].c = 6
                        dp[0][2].a = 7
                        dp[0][2].b = 8
                        dp[0][2].c = 9
                        dp[1][0].a = 10
                        dp[1][0].b = 11
                        dp[1][0].c = 12
                        dp[1][1].a = 13
                        dp[1][1].b = 14
                        dp[1][1].c = 15
                        dp[1][2].a = 16
                        dp[1][2].b = 17
                        dp[1][2].c = 18

                        (*tp)[0][0].a = 1
                        (*tp)[0][0].b = 2
                        (*tp)[0][0].c = 3
                        (*tp)[0][1].a = 4
                        (*tp)[0][1].b = 5
                        (*tp)[0][1].c = 6
                        (*tp)[0][2].a = 7
                        (*tp)[0][2].b = 8
                        (*tp)[0][2].c = 9
                        (*tp)[1][0].a = 10
                        (*tp)[1][0].b = 11
                        (*tp)[1][0].c = 12
                        (*tp)[1][1].a = 13
                        (*tp)[1][1].b = 14
                        (*tp)[1][1].c = 15
                        (*tp)[1][2].a = 16
                        (*tp)[1][2].b = 17
                        (*tp)[1][2].c = 18

.. card:: See Also

        * Current Module

                * :doc:`../basic_ptr`

        * Previous Module

                * :doc:`../../variable_and_ptr/variable_and_ptr`

        * Next Module

                * :doc:`../../array_n_ptrs/array_n_ptrs`

        * Other Modules

                * :doc:`../../malloc_ptr/malloc_ptr`
                * :doc:`../../typecasting_n_ptr/typecasting_n_ptr`
                * :doc:`../../funcs_n_ptrs/funcs_n_ptrs`
                * :doc:`../../memcpy_ptr/memcpy_ptr`
                * :doc:`../../const_ptr/const_ptr`
                * :doc:`../../void_ptr/void_ptr`
                * :doc:`../../array_of_ptr/array_of_ptr`
                * :doc:`../../ptr_to_array/ptr_to_array`
                * :doc:`../../function_ptr/function_ptr`
                * :doc:`../../pre_incr_ptr/pre_incr_ptr`
                * :doc:`../../post_incr_ptr/post_incr_ptr`
                * :doc:`../../pre_decr_ptr/pre_decr_ptr`
                * :doc:`../../post_decr_ptr/post_decr_ptr`