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 Null Pointer is a pointer that does not point to any memory location. It stores the base address of the segment. The null pointer stores the Null value while void is the type of the pointer.

A null pointer is a special reserved value that is defined in a stddef header file. Here, Null means that the pointer is referring to the 0th memory location.

If we do not have any address which is to be assigned to the pointer, then it is known as a null pointer. When a NULL value is assigned to the pointer, then it is considered as a Null pointer.

   Declare a pointer p of the integer datatype.

Let us see an example of how null pointers are created.

printf("The value of pointer assigned is : %x\n", ptr  );

Explanation: In the above code, we are initializing the variable “ptr”  to 0 (zero) so when we print the pointer value which Null pointer.

Suppose let us take another example where the pointer variables are not assigned to any memory address.

printf("Address of the given pointer variable: %d", pointer_var);

printf("Value of pointer variable is : %d", * pointer_var);

timeout: the monitored command dumped core

sh:  line 1:  15771 Segmentation fault         timeout 10s main

Explanation: In the above code, the pointer_var variable is not assigned to zero nor does it store any address of any variable in it, when the code is executed during the compile-time it gives an error where it throws garbage value which might harm your computer. So usually when we try to write or read from a null pointer we get a run time error as we saw in the above code which we get segmentation fault which is a null pointer exception sometimes it also throws an exception as a null pointer exception. In most of the examples, a null pointer is used to denote or indicate the end of the list.

To avoid this exception we can rewrite the above code as

printf("Value of pointer variable is : %d",* pointer_var);

Explanation: In the above-modified code, we assign a pointer_var to the “NULL” value and we check with the condition if the value of the pointer is null or not. In most the operating system, codes or programs are not allowed to access any memory which has its address as 0 because the memory with address zero 0is only reserved by the operating system as it has special importance, which states that the pointer is not intended to point to any memory location that can be accessible. So by default, we can say that if a pointer is assigned to zero then it is nothing but it only points to nothing.

A Null pointer is a pointer that is a variable with the value zero or an address leading to nothing in the C programming language. To make a variable a null pointer, we use the keyword NULL, which is a predefined macro in C. Also, after the data is no longer in use, the memory allocated to it must be released, or the dangling pointer would reappear. Also, never declare a pointer without first assigning NULL to it, as this will result in an error when the program is launched.

Let's discuss everything about the null pointer.

Everything  About Null Pointer 

As we know that we can create a pointer of any data type such as int, char, float, we can also create a pointer pointing to a function. The code of a function always resides in memory, which means that the function has some address. We can get the address of memory by using the function pointer.

Function_returntype ( *Pointer_name) ( argument_list)

First, we have to write the return type of function which can be void, double, etc. Then we have to give a name to our function pointer after that in another bracket we have to list the argument.

In the above syntax func_pointer is a pointer to a function taking an integer argument that will return void.

Let us have a look at the working of Function Pointer in the C programming language

Here is the C code to demonstrate the working of Function Pointer:

functiontopointer = sum ; // This part can also be done using void ( *fun_ptr ) ( int ) = &fun ;

//Here we are calling using the function pointer

int Output1 = functiontopointer (20, 98) ;

// Here we are calling function in normal way

printf ( " Calling through function pointer: %d " , Output1 ) ;

printf ( " \n Calling through function name: %d " , Output2 ) ;

Output 1 : Calling using the function pointer:  118

Output 2: Calling using the function name :  118 

Explanation: In the above code, you can see we have declared a method called Sum to add the two declared variables var1 and var2 and store the output of addition in Sum. In the main class, we have declared a function pointer FTP with an integer argument that returns void. Similarly, for using the function pointer functionality we are taking two inputs from the user. One is for showing the addition using function pointer while the other one is for showing the result using the normal pointer.

printf ( " The addition of both the input is %d \n " , i+j ) ;

printf ( " The substraction of both the input is %d\n " , i-j ) ;

printf ( " The multiplication of both the input is %d\n " , i*j ) ;

void ( *funcpointer_arr[] )( int , int ) = { addition, substraction, multiplication} ;

printf ( " Please enter: 0 for Add , 1 for Substract and 2 "

( *funcpointer_arr [ character ] ) ( i ,  j ) ;

Explanation: In the above code, you can see we are applying the same technique of function pointer as we did in the previous code. We have separately created functions for addition, multiplication, and subtraction. We have declared a function pointer named void ( *funcpointer_arr [] )( int, int ) to store the values separately for all the operations with two integer data types a and b. Therefore, based on the choices 0, 1, and 2 we can perform the preferred operation separately.

Here is another C code to demonstrate the working of Function Pointer:

int comparison ( const void* lhs , const void* rhs )

return ( * ( int * ) rhs - * ( int * ) lhs ) ;

int ( *cmp ) ( const void* , const void* ) ;

int array [] = {15,42,93,54,15,66,37,8,81} ;

qsort ( array, sizeof ( array ) / sizeof ( *array ) , sizeof ( *array ) , cmp ) ;

while ( x < sizeof ( array ) / sizeof ( *array ) )

Explanation: In the above code, you can see we have declared a function pointer named as the comparison in which we have two arguments of type constant named as LHS and RHS, and the function is declared as integer, therefore, it will return this value ( * ( int * ) RHS – *( int * ) LHS ). Then in the main class, we are calling our function parameter and declaring a *camp ( pointer ) to store the address value of the comparison function pointer. We have declared an array of integer data types in which we have defined some random values in a random sequence. Then we are using a quick sort method to sort the array in decreasing order sequence in output. Finally, until the while condition is satisfied it will print the compared value on by one. Once the while condition turns false it will stop and print the final sorted result.

Function pointer in C programming language can make code faster, easy, short, and efficient without occupying any large space in the code as the function pointer contains the start of the executable code. We can also use a function name to get the address of a function pointer.

In this blog, we'll know about the function pointer in C.

c program

Trending Blogposts on c program

Pointer in C

Everything About Null Pointer

Function Pointer in C

Popular Discussions on c program

PRODUCTS

QUICK LINKS

LEGAL

c program

Trending Blogposts on c program

Pointer in C

Everything About Null Pointer

Function Pointer in C

Popular Discussions on c program