Declaring and Initializing a pointer
In this tutorial, we will learn how to declare, initialize and use a pointer and also about NULL pointer and its uses.
Check these topics before continue reading:
Declaration of C Pointer variable
The general syntax of pointer declaration is,
datatype *pointer_name;
The data type of the pointer and the variable to which the pointer variable is pointing must be the same.
Initialization of C Pointer variable
Pointer Initialization is the process of assigning address of a variable to a pointer variable. It contains the address of a variable of the same data type. In C language address operator & is used to determine the address of a variable. The & (immediately preceding a variable name) returns the address of the variable associated with it.
int a = 10;
int *ptr; //pointer declaration
ptr = &a; //pointer initialization
Pointer variable always points to variables of the same datatype. For example:
float a;
int *ptr = &a; // ERROR, type mismatch
While declaring a pointer variable, if it is not assigned to anything then it contains garbage value. Therefore, it is recommended to assign a NULL value to it,
A pointer that is assigned a NULL value is called a NULL pointer in C.
int *ptr = NULL;
Using the pointer or Dereferencing of Pointer
Once a pointer has been assigned the address of a variable, to access the value of the variable, the pointer is dereferenced, using the indirection operator or dereferencing operator *. Consider the following example for better understanding.
#include <stdio.h>
int main()
{
int a;
a = 10;
int *p = &a; // declaring and initializing the pointer
//prints the value of 'a'
printf("%d\n", *p);
printf("%d\n", *&a);
//prints the address of 'a'
printf("%u\n", &a);
printf("%u\n", p);
printf("%u\n", &p); //prints address of 'p'
return 0;
}
10
10
3795480300
3795480300
3795480304
Points to remember while using pointers
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While declaring/initializing the pointer variable, * indicates that the variable is a pointer.
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The address of any variable is given by preceding the variable name with Ampersand &.
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The pointer variable stores the address of a variable.
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The declaration int *a doesn't mean that a is going to contain an integer value. It means that a is going to contain the address of a variable storing integer value.
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To access the value of a certain address stored by a pointer variable * is used. Here, the * can be read as 'value at'.
Since we have learned the basics of Pointers in C, you can check out some C programs using pointer.
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