The Pointer in C is a variable that stores the address of another variable. A pointer can also be used to refer to another pointer function. A pointer can be incremented/decremented, i.e., to point to the next/ previous memory location. The purpose of a pointer is to save memory space and achieve faster execution time.

Different Ways of Accessing Variable Address in C

Let us try to know what are the different ways by which we can print the address of a variable in C.

There are two ways by which we can actually print the address of a variable. Those two methods are:

Let us look into each method with an example

In this method, we will be using the concept of the ampersand to print the address of a variable.

printf("The address of variable varNumValue: %x\n", &varNumValue  );

printf("varTextValue variable address is : %x\n", &varTextValue  );

Now, copy the above code snippet and run it

The address of variable varNumValue: a0665a48

The address of variable varTextValue is : a0665a3e

Although, one might see the different value which is assigned randomly while running the example

The above-mentioned example is not much used, but it is worth knowing. Now let us look to the other concept which we are discussing in this topic.

This is a modern approach to access the address of a variable. Before using a pointer, let us know the general syntax of declaring a pointer.

The general syntax of declaring a pointer – A common syntax which we use for declaring a variable is:

This is a common way to declare any pointer in C, here data_type represents the type of the variable whose address needs to be stored. * denotes that the variable declared is a pointer. a variable is simply used for accessing the value

After discussing the concept of the General syntax of declaring a pointer, let us know how we can use a pointer in programming.

To use a pointer in C, basically, one needs to follow the following three steps:

Assigning the address of the variable whose address we want to hold in the pointer variable

Now, once we have a pointer variable with the address, we can again retrieve the value of the variable from the address stored in the pointer. This could be done using is simply one of the unary operators in C.

Let us use the above-mentioned steps with an example, and then we will explain this example step by step.

printf("Address of the variable varNumValue is: %x\n", &varNumValue  );

printf("Address stored in the variable ipointervarNumValue is: %x\n", ipointervarNumValue);

printf("Value of the variable *ipointervarNumValue is: %d\n", *ipointervarNumValue );

Address of the variable varNumValue is: bf7b7f94

Address stored in the variable ipointervarNumValue is: bf7b7f94

Value of the variable *ipointervarNumValue is: 10

Now, let us try to understand the above example

The line int  varNumValue = 10; simply declares a variable with value 10

The second line that is a line next to it: int  * ipointervarNumValue; is simply declared to store the address of the variable

The next code snippet, which is: ipointervarNumValue = &varNumValue, is used to hold the address of the variable. Here, we are using the concept of an ampersand, which we discussed earlier in the article

Now, we can simply get the value and use a pointer in our code snippet

Now, let us look into different types of a pointer in C

Different types of pointers in C are following:

We can create a null pointer by assigning null value during the pointer declaration. This method is useful when you do not have any address assigned to the pointer. A null pointer always contains value 0.

Following program illustrates the use of a null pointer:

	printf(“The value inside variable p is:\n%x”,p);

In C programming, a void pointer is also called as a generic pointer. It does not have any standard data type. A void pointer is created by using the keyword void. It can be used to store an address of any variable.

Following program illustrates the use of a void pointer:

printf("The size of pointer is:%d\n",sizeof(p));

Today we'll discuss what a pointer is and what's its use.

Pointer in C

A pointer in c is an address, which is a numeric value. Therefore, you can perform arithmetic operations on a pointer just as you can on a numeric value. There are four arithmetic operators that can be used on pointers: ++, --, +, and -

To understand pointer arithmetic, let us consider that ptr is an integer pointer which points to the address 1000. Assuming 32-bit integers, let us perform the following arithmetic operation on the pointer −

After the above operation, the ptr will point to the location 1004 because each time ptr is incremented, it will point to the next integer location which is 4 bytes next to the current location. This operation will move the pointer to the next memory location without impacting the actual value at the memory location. If ptr points to a character whose address is 1000, then the above operation will point to location 1001 because the next character will be available at 1001.

We prefer using a pointer in our program instead of an array because the variable pointer can be incremented, unlike the array name which cannot be incremented because it is a constant pointer. The following program increments the variable pointer to access each succeeding element of the array −

   /* let us have array address in pointer */

      printf("Address of var[%d] = %x\n", i, ptr );

      printf("Value of var[%d] = %d\n", i, *ptr );

The same considerations apply to decrementing a pointer, which decreases its value by the number of bytes of its data type as shown below −

      printf("Address of var[%d] = %x\n", i-1, ptr );

      printf("Value of var[%d] = %d\n", i-1, *ptr );

      /* move to the previous location */

We cannot add the two pointers, as it would also result in the address of an unknown memory location. So there is no use of it. But we can add any integer value to the pointer in order to point to that memory location. Addition of integer value works according to the datatype of the value pointer pointing to using ptr+x. For example, if the pointer holds the address of any integer value (64 – bit integer system having 4 bytes integer), on adding +2 in it, it will increment the value by 8 bytes.

// pointer 'ptr' to point the above 'num' and 'ptr1' to point 'a'

// pointer 'ptr' holding the address of 'num' location and 'ptr1' to hold the address of character 'a'

printf("\n The address which the pointer holds is %u",ptr);

printf("\n The address which the pointer holds is %u",ptr1);

// adding the integer value 4 to the pointer value

// Pointer address will now gets incremented by 4*8 bytes as it holds the address of double value

printf("\n Now the address which the pointer holds is %u",ptr);

// Pointer address will now gets incremented by 4*1 bytes as it holds the address of character value

printf("\n Now the address which the pointer holds is %u",ptr1);

The address which the pointer holds is 322376700

The address which the pointer holds is 3223766999

Now the address which the pointer holds is 3223767032

Now the address which the pointer holds is 3223767003

Subtraction in case of pointers is possible with two addresses (i.e. with 2 pointer values) as well as subtraction of an integer value from the pointer. Subtraction of an integer value from the pointer works similar to the addition of integer value as discussed above, i.e. any integer value can be subtracted from the pointer using ptr-x. And it will result the difference of pointer by x * bytes of value datatype hold by pointer.

In this article, we'll know about the pointer arithmetic of C.

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