What is the role of Declaring a Pointer in C programming

Declaring a Pointer 

In this article, we are trying to understand the role of Declaring a Pointer in C, with program.

 

Declaring A Pointer

•  Pointing variables, must be declared before they may be used in a C program.
• When a pointer variable is declared, the variable name must be preceded by asterisk(*).
• The data type that appears in the declaration refers to the data item that is stored in the address represented by the pointer.
• Pointer variables can point to numeric or character variable, arrays, functions, other pointer variables, or null (zero) value.

 

Usage:

 data-type *pointer_variable;

• data-type refers to the data type of the pointer's object.
• *pointer_variable is the name of the pointer variable.
• Within a variable declaration, a pointer variable can be initialized by assigning it the address of another variable.

 

Program-1 

Difference between ordinary arithmetic expression & Declaring a Pointer

#include <stdio.h> 

/*Difference between ordinary arithmetic expression & Declaring a Pointer. */

void main()

{        int num1, num2;

          int value=3;

          int *value_pointer;                /*value_pointer points to value */

          num1 =2 * (value+5);                /* arithmetic expression */

          value_pointer =&value;

          num2 = 2 * (*value_pointer+5);

         printf("\nNum1 = %d  Num2 = %d", num1, num2);

         }

Run

Num 1 = 16  Num2 = 16

Explanation: 

There are 2 integer expressions in the above program. The first, 2 * (value + 5), is an ordinary arithmetic expression, while the second, 2 * (*value_pointer + 5), involves the use of pointers. Still, the  expressions are equal to each other because value and *value_pointer each represent the same integer value.

 Program-2

Assigning a value to a variable

#include <stdio.h> 

/*Assigning a value to a variable */

void main()

{        int value=3;

          int *value_pointer;               

          value_pointer =&value;

         printf("\n *Value_pointer = %d  Value = %d", *value_pointer, value);

         *value_pointer = 7;

         printf("\n *Value_pointer = %d  Value = %d", *value_pointer, value);

         }

Run

*Value_pointer = 3  Value  = 3

*Value_pointer = 3  Value  = 3

 

Explanation:

• Assign an initial value of 3 to the integer variable value
• Assign the address of value to the pointer variable value_pointer 

                  So, Value_pointer becomes a pointer to value
                 The expression *value_pointer represents the value 3

• The first printf statement displays the current values of *value_pointer and value
•  The value of *value_pointer is reset to 7

                 So, value will be reassigned the value 7

• The second printf statement displays the new values of *value_pointer and value.

     

Exercise regularly. Eat a nutritious diet. Don't smoke - WHO (Covid-19).

See also...

• Learn how to write the  C program step-by-step | Lesson -1
• Learn how to write the  C program step-by-step | Lesson -2   
• Learn how to write the  C program step-by-step | Lesson -3
• Learn how to write the  C program step-by-step | Lesson -4
• Learn how to write the  C program step-by-step | Lesson -5 
• Learn how to write the  C program step-by-step | Lesson -6 
• Learn how to write the  C program step-by-step | Lesson -7

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Thanks a lot for reading.

Neel Kamal