pre decrement char single pointer
====================================

In this section, you are going to learn

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		How to iterate character strings using ``--ptr`` ?

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		What is the meaning of ``--ptr``, ``*--ptr``, ``*(--ptr)``, ``*--(ptr)``, ``--(*ptr)``, ``--*ptr`` ?

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		What is the meaning of ``c = --ptr``, ``c = *--ptr``, ``c = *(--ptr)``, ``c = *--(ptr)``, ``c = --(*ptr)``, ``c = --*ptr`` ?

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		What is the difference between ``--ptr``, ``*--ptr``, ``*(--ptr)``, ``*--(ptr)``, ``--(*ptr)``, ``--*ptr`` ?

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		What is the difference between ``c = --ptr``, ``c = *--ptr``, ``c = *(--ptr)``, ``c = *--(ptr)``, ``c = --(*ptr)``, ``c = --*ptr`` ?

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		Topics of Pre Decrement

		* :ref:`Basics of Pre Decrement <pre_decr_char_sp_mt_1>`
		* :ref:`Meaning of expressions <pre_decr_char_sp_mt_2>`
		* :ref:`Summary of expressions <pre_decr_char_sp_mt_3>`
		* :ref:`Pre Decrement : char pointer inside structure <pre_decr_char_sp_mt_4>`
		* :ref:`Pre Decrement : Function Call <pre_decr_char_sp_mt_5>`

.. _pre_decr_char_sp_mt_1:

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		Basics of Pre Decrement

		* :ref:`- -ptr Basic Usage <pre_decr_char_sp_ex_1>`
		* :ref:`- -ptr : Iterate and print characters of a string : Method 1 <pre_decr_char_sp_ex_2>`
		* :ref:`- -ptr : Iterate and print characters of a string : Method 2 <pre_decr_char_sp_ex_3>`
		* :ref:`- -ptr : Iterate and print characters of a string : Method 3 <pre_decr_char_sp_ex_4>`
		* :ref:`- -ptr : Iterate and print characters of a string : Method 4 <pre_decr_char_sp_ex_5>`

.. _pre_decr_char_sp_ex_1:

.. tab-set::

        .. tab-item:: Example 1 : ``--ptr`` : Basic Usage

		* Step 1 : Define a Single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Point ``ptr`` to Single dimension array

		.. code-block:: c

		        char *ptr;

		        ptr = a + strlen(a) - 1;

		* Step 3 : Decrement ``ptr``

		.. code-block:: c

		        --ptr;

		* Step 4 : Print ``*ptr``

		.. code-block:: c

		        printf("*ptr = %c\n", *ptr);

		* See full program below

		.. code-block:: c

			#include <stdio.h>

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a) - 1;

			        --ptr;

			        printf("*ptr = %c\n", *ptr);

			        return 0;
			}

		* Output is as below

		.. code-block:: c

			*ptr = o

.. _pre_decr_char_sp_ex_2:

.. tab-set::

        .. tab-item:: Example 2 : ``--ptr`` : Iterate and print characters of a string : Method 1

		* Step 1 : Define a Single Dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Point ``ptr`` to Single dimension array

		.. code-block:: c

		        char *ptr;

		        ptr = a + strlen(a) - 1;

		* Step 3 : Print string by iterating through all characters using ``--ptr``

		.. code-block:: c

		        for (int i = 0; i < strlen(a); i++)
		        {   
		                printf("*ptr = %c\n", *ptr);
		                --ptr;
		        }

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a) - 1;

			        for (int i = 0; i < strlen(a); i++)
			        {   
			                printf("*ptr = %c\n", *ptr);
			                --ptr;
			        }

			        return 0;
			}

		* Output is as below

		.. code-block:: c

			*ptr = p
			*ptr = o
			*ptr = t
			*ptr = p
			*ptr = a
			*ptr = L

.. _pre_decr_char_sp_ex_3:

.. tab-set::

        .. tab-item:: Example 3 : ``--ptr`` : Iterate and print characters of a string : Method 2

		* Step 1 : Define a Single Dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Point ``ptr`` to Single dimension array

		.. code-block:: c

		        char *ptr;

		        ptr = a + strlen(a) - 1;

		* Step 3 : Print string by iterating through all characters using ``--ptr``

		.. code-block:: c

		        while (ptr >= a)
		        {
		                printf("*ptr = %c\n", *ptr);
		                --ptr;
		        }

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a) - 1;

			        while (ptr >= a)
			        {
			                printf("*ptr = %c\n", *ptr);
			                --ptr;
			        }

			        return 0;
			}

		* Output is as below

		.. code-block:: c

			*ptr = p
			*ptr = o
			*ptr = t
			*ptr = p
			*ptr = a
			*ptr = L

.. _pre_decr_char_sp_ex_4:

.. tab-set::

        .. tab-item:: Example 4 : ``--ptr`` : Iterate and print characters of a string : Method 3

		* Step 1 : Define a Single Dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Point ``ptr`` to Single dimension array

		.. code-block:: c

		        char *ptr;

		        ptr = a + strlen(a);

		* Step 3 : Print string by iterating through all characters using ``--ptr``

		.. code-block:: c

		        while (ptr > a)
		        {
		                char c;

		                c = *--ptr;

		                printf("*ptr = %c\n", c); 
       			}

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

			        while (ptr > a)
			        {
			                char c;

			                c = *--ptr;

			                printf("*ptr = %c\n", c); 
        			}

			        return 0;
			}

		* Output is as below

		.. code-block:: c

			*ptr = p
			*ptr = o
			*ptr = t
			*ptr = p
			*ptr = a
			*ptr = L

		.. dropdown:: Guess what is going on ?

			* Statement ``c = *--ptr`` can be understood in two steps

				* Step 1 : Decrement ``ptr``

				* Step 2 : Assign ``*ptr`` to ``c``

.. _pre_decr_char_sp_ex_5:

.. tab-set::

        .. tab-item:: Example 5 : ``--ptr`` : Iterate and print characters of a string : Method 4

		* Step 1 : Define a Single Dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Point ``ptr`` to Single dimension array

		.. code-block:: c

		        char *ptr;

		        ptr = a + strlen(a);

		* Step 3 : Print string by iterating through all characters using ``--ptr``

		.. code-block:: c

		        while (ptr > a)
		        {
		                printf("*ptr = %c\n", *--ptr);
		        }

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

			        while (ptr > a)
			        {
			                printf("*ptr = %c\n", *--ptr);
			        }

			        return 0;
			}

		* Output is as below

		.. code-block:: c

			*ptr = p
			*ptr = o
			*ptr = t
			*ptr = p
			*ptr = a
			*ptr = L

		.. dropdown:: Guess what is going on ?

			* Statement ``printf("*ptr = %c\n", *--ptr);`` can be understood in two steps

				* Step 1 : Decrement ``ptr``

				* Step 2 : Pass ``*ptr`` as arguement to ``printf``

.. _pre_decr_char_sp_mt_2:


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		Meaning of expressions

		* :ref:`Meaning of --ptr and c = --ptr <pre_decr_char_sp_ex_6>`
		* :ref:`Meaning of *--ptr and c = *--ptr <pre_decr_char_sp_ex_7>`
		* :ref:`Meaning of *(--ptr) and c = *(--ptr) <pre_decr_char_sp_ex_10>`
		* :ref:`Meaning of *--(ptr) and c = *--(ptr) <pre_decr_char_sp_ex_8>`
		* :ref:`Meaning of --*ptr and c = --*ptr <pre_decr_char_sp_ex_9>`
		* :ref:`Meaning of --(*ptr) and c = --(*ptr) <pre_decr_char_sp_ex_11>`


.. _pre_decr_char_sp_ex_6:

.. tab-set::

        .. tab-item:: Meaning of ``--ptr`` and ``c = --ptr``

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			* Consider statement 

			.. code-block:: c

				p = --ptr;

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``ptr`` is assigned to ``p``

			* We now derived a rule

				* First Decrement, then Assign

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Define a single pointer and point to array

		.. code-block:: c

			char *ptr;

			ptr = a + strlen(a);

		OR

		.. code-block:: c

			char *ptr;

			ptr = &a[0];

		* Step 3 : Iterate and print the string

		.. code-block:: c

			while (ptr > a)
			{
				char *p; 

				p = --ptr;

				printf("*p = %c\n", *p);
			}


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			Can you guess what is happening ?

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			* Let us Recall 

			.. code-block:: c

				p = --ptr;

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``ptr`` is assigned to ``p``

			* We now derived a rule

				* First Decrement, then Assign

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

				while (ptr > a)
				{
					char *p; 

					p = --ptr;

					printf("*p = %c\n", *p);
				}

			        return 0;
			}

		Output is as below

		.. code-block:: c

			*p = p
			*p = o
			*p = t
			*p = p
			*p = a
			*p = L

.. _pre_decr_char_sp_ex_7:

.. tab-set::

        .. tab-item:: Meaning of ``*(--ptr)`` and ``c = *(--ptr)``

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			* Consider statement 

			.. code-block:: c

				c = *(--ptr);

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``*ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Define a single pointer and point to array

		.. code-block:: c

			char *ptr;

			ptr = a + strlen(a);

		OR

		.. code-block:: c

			char *ptr;

			ptr = &a[0];

		* Step 3 : Iterate and print the string

		.. code-block:: c

			while (ptr > a)
			{
				char c;

				c = *(--ptr);

				printf("c = %c\n", c);
			}


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			Can you guess what is happening ?

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			* Let us Recall

			.. code-block:: c

				c = *(--ptr);

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``*ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

				while (ptr > a)
				{
					char c;

					c = *(--ptr);

					printf("c = %c\n", c);
				}

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_10:

.. tab-set::

        .. tab-item:: Meaning of ``*--ptr`` and c = ``*--ptr``

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			* :ref:`Same as *(--ptr) and c = *(--ptr) <pre_decr_char_sp_ex_7>`

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			* Consider statement 

			.. code-block:: c

				c = *--ptr;

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``*ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Define a single pointer and point to array

		.. code-block:: c

			char *ptr;

			ptr = a + strlen(a);

		OR

		.. code-block:: c

			char *ptr;

			ptr = &a[0];

		* Step 3 : Iterate and print the string

		.. code-block:: c

			while (ptr > a)
			{
				char c;

				c = *--ptr;

				printf("c = %c\n", c);
			}

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			Can you guess what is happening ?

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			* Let us Recall

			.. code-block:: c

				c = *--ptr;

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``*ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

				while (ptr > a)
				{
					char c;

					c = *--ptr;

					printf("c = %c\n", c);
				}

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_8:

.. tab-set::

        .. tab-item:: Meaning of ``*--(ptr)`` and ``c = *--(ptr)``

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			* :ref:`Same as *(--ptr) and c = *(--ptr) <pre_decr_char_sp_ex_7>`

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			* Consider statement 

			.. code-block:: c

				c = *--(ptr);

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``*ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Define a single pointer and point to array

		.. code-block:: c

			char *ptr;

			ptr = a + strlen(a);

		OR

		.. code-block:: c

			char *ptr;

			ptr = &a[0];

		* Step 3 : Iterate and print the string

		.. code-block:: c

			while (ptr > a)
			{
				char c;

				c = *--(ptr);

				printf("c = %c\n", c);
			}


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			Can you guess what is happening ?


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			* Let us Recall

			.. code-block:: c

				c = *--(ptr);

			* There are two steps in this statement

				* ``ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``*ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

		* See full program below

		.. code-block:: c

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

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

				while (ptr > a)
				{
					char c;

					c = *--(ptr);

					printf("c = %c\n", c);
				}

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_9:

.. tab-set::

        .. tab-item:: Meaning of ``--*ptr`` and ``c = --*ptr``

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			* Consider statement 

			.. code-block:: c

				c = --*ptr;

			* There are two steps in this statement

				* ``*ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

.. _pre_decr_char_sp_ex_11:

.. tab-set::

        .. tab-item:: Meaning of ``--(*ptr)`` and ``c = --(*ptr)``

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			:column: col-lg-12 p-2
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			* Consider statement 

			.. code-block:: c

				c = --(*ptr);

			* There are two steps in this statement

				* ``*ptr`` is decremented

				* Current value of ``*ptr`` is assigned to ``c``

				* ``ptr`` is NOT decremented

			* We now derived a rule

				* First Decrement, then Assign

.. _pre_decr_char_sp_mt_3:


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		Summary of expressions

		* :ref:`Summary of Pre Decrement expressions <pre_decr_char_sp_ex_summary>`


.. _pre_decr_char_sp_ex_summary: 


.. tab-set::

        .. tab-item:: Summary of Pre Decrement expressions

		===================================== =========================================================================
		Expression                            Explanation
		===================================== =========================================================================
		c = --ptr			      * Decrement ``ptr``
						      * Assign ``ptr`` to ``c``
		c = \*--ptr		              * Decrement ``ptr``
						      * Assign ``*ptr`` to ``c``
						      * DO NOT decrement ``*ptr``
		c = \*(--ptr)		              * Decrement ``ptr``
						      * Assign ``*ptr`` to ``c``
						      * DO NOT decrement ``*ptr``
		c = \*--(ptr)		              * Decrement ``ptr``
						      * Assign ``*ptr`` to ``c``
						      * DO NOT decrement ``*ptr``
		c = --\*ptr		              * Decrement ``*ptr``
						      * Assign ``*ptr`` to ``c``
						      * DO NOT decrement ``ptr``
		c = --\*(ptr)		              * Decrement ``*ptr``
						      * Assign ``*ptr`` to ``c``
						      * DO NOT decrement ``ptr``
		===================================== =========================================================================


.. _pre_decr_char_sp_mt_4:

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		Pre Decrement : char pointer inside structure

		* :ref:`Char pointer accessed using Structure Object <pre_decr_char_sp_ex_struct_ex_1>`
		* :ref:`Char pointer accessed using Structure Single Pointer <pre_decr_char_sp_ex_struct_ex_2>`
		* :ref:`Char pointer accessed using Structure Double Pointer <pre_decr_char_sp_ex_struct_ex_3>`
		* :ref:`Char pointer accessed using Structure Triple Pointer <pre_decr_char_sp_ex_struct_ex_4>`
		* :ref:`Char pointer accessed using Nested Structure Object <pre_decr_char_sp_ex_struct_ex_5>`
		* :ref:`Char pointer accessed using Nested Structure Single Pointer <pre_decr_char_sp_ex_struct_ex_6>`
		* :ref:`Char pointer accessed using Nested Structure 2 level Pointers <pre_decr_char_sp_ex_struct_ex_7>`


.. _pre_decr_char_sp_ex_struct_ex_1:

.. tab-set::

        .. tab-item:: Char pointer accessed using Structure Object

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Create a structure object

		.. code-block:: c

			struct ABC abc;

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

			abc.ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while (abc.ptr > a)
		        {   
		                char c;

		                c = *--abc.ptr;

		                printf("c = %c\n", c); 
       			}

		* See full program below

		.. code-block:: c

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

			struct ABC
			{
			        char *ptr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

				struct ABC abc;

			        abc.ptr = a + strlen(a);

				while (abc.ptr > a)
				{   
					char c;

					c = *--abc.ptr;

					printf("c = %c\n", c); 
				}

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_struct_ex_2:

.. tab-set::

        .. tab-item:: Char pointer accessed using Structure Single Pointer

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Allocate memory for structure pointers

		.. code-block:: c

			struct ABC *sp;

			sp = malloc(sizeof(struct ABC));

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

			sp->ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while (sp->ptr > a)
		        {
		                char c;

		                c = *--sp->ptr;

		                printf("c = %c\n", c); 
		        }

		* Step 5 : Free memory after use

		.. code-block:: c

		        free(sp);

		* See full program below

		.. code-block:: c

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

			struct ABC 
			{
			        char *ptr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

			        struct ABC *sp;

			        sp = malloc(sizeof(struct ABC));

			        sp->ptr = a + strlen(a);

				while (sp->ptr > a)
				{
					char c;

					c = *--sp->ptr;

					printf("c = %c\n", c); 
				}

			        free(sp);

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_struct_ex_3:

.. tab-set::

        .. tab-item:: Char pointer accessed using Structure Double Pointer

		* Step 1 : Define a single dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Allocate memory for structure pointers

		.. code-block:: c

		        struct ABC **dp;

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

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

		        (*dp)->ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while ((*dp)->ptr > a)
		        {
		                char c;

		                c = *--(*dp)->ptr;

		                printf("c = %c\n", c); 
		        }

		* Step 5 : Free memory after use

		.. code-block:: c

		        free(*dp);
		        free(dp);

		* See full program below

		.. code-block:: c

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

			struct ABC 
			{
			        char *ptr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

			        struct ABC **dp;

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

			        (*dp)->ptr = a + strlen(a);

			        while ((*dp)->ptr > a)
			        {
			                char c;

			                c = *--(*dp)->ptr;

			                printf("c = %c\n", c); 
			        }

			        free(*dp);
			        free(dp);

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_struct_ex_4:

.. tab-set::

        .. tab-item:: Char pointer accessed using Structure Triple Pointer


		* Step 1 : Define a single dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Allocate memory for structure pointers

		.. code-block:: c

		        struct ABC ***dp;

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

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

		        (**dp)->ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while ((**dp)->ptr > a)
		        {
		                char c;

		                c = *--(**dp)->ptr;

		                printf("c = %c\n", c); 
		        }

		* Step 5 : Free memory after use

		.. code-block:: c

		        free(**dp);
		        free(*dp);
		        free(dp);

		* See full program below

		.. code-block:: c

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

			struct ABC
			{
			        char *ptr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

			        struct ABC ***dp;

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

			        (**dp)->ptr = a + strlen(a);

			        while ((**dp)->ptr > a)
			        {
			                char c;

			                c = *--(**dp)->ptr;

			                printf("c = %c\n", c); 
			        }

			        free(**dp);
			        free(*dp);
			        free(dp);

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_struct_ex_5:

.. tab-set::

        .. tab-item:: Char pointer accessed using Nested Structure Object

		* Step 1 : Define a single dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Create a structure object

		.. code-block:: c

		        struct ABC abc;

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

			abc.pqr.ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while (abc.pqr.ptr > a)
		        {
		                char c;

		                c = *--abc.pqr.ptr;

		                printf("c = %c\n", c); 
		        }

		* See full program below

		.. code-block:: c

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

			struct PQR
			{
			        char *ptr;
			};

			struct ABC 
			{
			        struct PQR pqr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

			        struct ABC abc;

			        abc.pqr.ptr = a + strlen(a);

			        while (abc.pqr.ptr > a)
			        {
			                char c;

			                c = *--abc.pqr.ptr;

			                printf("c = %c\n", c); 
			        }

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_struct_ex_6:

.. tab-set::

        .. tab-item:: Char pointer accessed using Nested Structure Single Pointer

		* Step 1 : Define a single dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Allocate memory for structure pointers

		.. code-block:: c

		        struct ABC *sp;

		        sp = malloc(sizeof(struct ABC));

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

		        sp->pqr.ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while (sp->pqr.ptr > a)
		        {
		                char c;

		                c = *--sp->pqr.ptr;

		                printf("c = %c\n", c); 
		        }

		* Step 5 : Free memory after use

		.. code-block:: c

		        free(sp);

		* See full program below

		.. code-block:: c

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

			struct PQR 
			{
			        char *ptr;
			};

			struct ABC 
			{
			        struct PQR pqr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

			        struct ABC *sp;

			        sp = malloc(sizeof(struct ABC));

			        sp->pqr.ptr = a + strlen(a);

			        while (sp->pqr.ptr > a)
			        {
			                char c;

			                c = *--sp->pqr.ptr;

			                printf("c = %c\n", c); 
			        }

			        free(sp);

			        return 0;
			}

		Output is as below

		.. code-block:: c
 
			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_ex_struct_ex_7:

.. tab-set::

        .. tab-item:: Char pointer accessed using Nested Structure 2 level Pointers 

		* Step 1 : Define a single dimension array

		.. code-block:: c

		        char a[7] = "Laptop";

		* Step 2 : Allocate memory for structure pointers

		.. code-block:: c

		        struct ABC *abc;

		        abc = malloc(sizeof(struct ABC));
		        abc->pqr = malloc(sizeof(struct PQR));

		* Step 3 : Point single character pointer to single dimension array

		.. code-block:: c

		        abc->pqr->ptr = a + strlen(a);

		* Step 4 : Iterate through single dimension array using pointer

		.. code-block:: c

		        while (abc->pqr->ptr > a)
		        {
		                char c;

		                c = *--abc->pqr->ptr;

		                printf("c = %c\n", c); 
        		}

		* Step 5 : Free memory after use

		.. code-block:: c

		        free(abc->pqr);
		        free(abc);

		* See full program below

		.. code-block:: c

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

			struct PQR
			{
			        char *ptr;
			};

			struct ABC
			{
			        struct PQR *pqr;
			};

			int main(void)
			{
			        char a[7] = "Laptop";

			        struct ABC *abc;

			        abc = malloc(sizeof(struct ABC));
			        abc->pqr = malloc(sizeof(struct PQR));

			        abc->pqr->ptr = a + strlen(a);

			        while (abc->pqr->ptr > a)
			        {
			                char c;

			                c = *--abc->pqr->ptr;

			                printf("c = %c\n", c); 
        			}

			        free(abc->pqr);
			        free(abc);

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_mt_5:


	.. panels::
		:container: container pb-4
		:column: col-lg-12 p-2
		:card: shadow

		Pre Decrement : Function Call

		* :ref:`*--ptr : Function Call <pre_decr_char_sp_call_by_value_ex_1>`
		* :ref:`--ptr : Function Call <pre_decr_char_sp_call_by_value_ex_2>`


.. _pre_decr_char_sp_call_by_value_ex_1:

.. tab-set::

        .. tab-item:: \*--ptr : Function Call

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Define a single pointer and point to array

		.. code-block:: c

			char *ptr;

			ptr = a + strlen(a);

		* Step 3 : Iterate array using --ptr and Pass by Value

		.. code-block:: c

			while (ptr > a)
			{
				fun(*--ptr);
			}

		* Step 4 : Define a function ``fun`` which receives a character from caller

		.. code-block:: c

			void fun(char c)
			{
				printf("c = %c\n", c);
			}

		.. panels::
			:container: container pb-4
			:column: col-lg-12 p-2
			:card: shadow

			Let us Recall,

			* In case of ``*--ptr``

				* ``ptr`` is decremented first, then current value of ``*ptr`` is assigned
			
			* Hence, in this case

				* ``ptr`` is decremented first, then Current value of ``*ptr`` is passed to function ``fun``

		* See full program below

		.. code-block:: c

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

			void fun(char c)
			{
			        printf("c = %c\n", c); 
			}

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

			        while (ptr > a)
			        {
			                fun(*--ptr);
			        }

			        return 0;
			}

		Output is as below

		.. code-block:: c

			c = p
			c = o
			c = t
			c = p
			c = a
			c = L

.. _pre_decr_char_sp_call_by_value_ex_2:

.. tab-set::

        .. tab-item:: --ptr : Function Call

		* Step 1 : Define a single dimension array

		.. code-block:: c

			char a[7] = "Laptop";

		* Step 2 : Define a single pointer and point to array

		.. code-block:: c

			char *ptr;

			ptr = a + strlen(a);

		* Step 3 : Iterate array using --ptr and Pass by Value

		.. code-block:: c

			while (ptr > a)
			{
				fun(--ptr);
			}

		* Step 4 : Define a function ``fun`` which receives a character pointer from caller

		.. code-block:: c

			void fun(char *c)
			{
				printf("*c = %c\n", *c);
			}

		.. panels::
			:container: container pb-4
			:column: col-lg-12 p-2
			:card: shadow

			Let us Recall,

			* In case of ``--ptr``

				* ``ptr`` is decremented first, then decremented
			
			* Hence, in this case

				* ``ptr`` is decremented first, then passed to function ``fun``

		* See full program below

		.. code-block:: c

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

			void fun(char *c)
			{
			        printf("*c = %c\n", *c);
			}

			int main(void)
			{
			        char a[7] = "Laptop";

			        char *ptr;

			        ptr = a + strlen(a);

			        while (ptr > a)
			        {
			                fun(--ptr);
			        }

			        return 0;
			}

		Output is as below

		.. code-block:: c

			*c = p
			*c = o
			*c = t
			*c = p
			*c = a
			*c = L

.. card:: See Also

        * Current Module

                * :doc:`../pre_decr_ptr`

        * Previous Module

                * :doc:`../../post_incr_ptr/post_incr_ptr`

        * Next Module

                * :doc:`../../post_decr_ptr/post_decr_ptr`

        * Other Modules

                * :doc:`../../variable_and_ptr/variable_and_ptr`
                * :doc:`../../array_n_ptrs/array_n_ptrs`
                * :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:`../../pre_incr_ptr/pre_incr_ptr`