Pointers in C Programming

In this tutorial, you are going to learn about Pointers in C Programming.

Pointers in C Programming

• Pointers are variables like any other type. However they are also derived type like arrays.
• Just like other variables, it is mandatory to declare pointers before using them.
• Pointers can be used to hold “memory address” of other variables of a given type.
• However just like, each variable has a type, pointers also have type, like:
  • Pointer to an int - It can be used to hold addresses of only and only int variables
  • Pointer to a char - holds addresses of only and only char.

Pointers are variables that contain memory addresses as their values. A variable name directly references a value. A pointer indirectly references a value.  Referencing a value through a pointer is called indirection. A pointer variable must be declared before it can be used.

Concept of Address and Pointers

• Memory can be conceptualized as a linear set of data locations.
• Variables reference the contents of locations.
• Pointers have a value at the address of a given location.
• Pointer is a value that points to a location in the memory
• Pointer is associated with a type

Operators used in Pointers

& - "address operator" which gives or produces the memory address of a data variable.

* - "dereferencing operator" which provides the contents in the memory location specified by a pointer.

Pointer Variable Definition

Basic syntax: Type *Name

Examples:

int *P;    /* P is var that can point to an int var */

float *Q;  /* Q is a float pointer */

char *R;   /* R is a char pointer */

Complex example:

int *AP[5];   /* AP is an array of 5 pointers to ints */

Examples of pointer declarations:

int  *a;

float *b;

char *c;

The asterisk, when used as above in the declaration, tells the compiler that the variable is to be a pointer, and the type of data that the pointer points to.

Pointer Initialization and Dereferencing Pointer

• You need to set proper values (address) to pointers just like you set values for variables, before you can use them.
• Initialize them at the time of declaration with address of a known variable, example

Method 1: If not initialized, it can later be assigned an address of any variable of the same type, before using it

int *j;

j = &i;                /* assign address

Method 2:

int *j = &i;            /* initialized to address of i.


Note: i should only be of type int and should already be defined or declared

Here ‘&’ is acting as “address of” operator.

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This post on Pointers in C Programming is written by Ritika Nagar (BCA, Sharda University). If you like TheCode11, then do follow us on Facebook, Twitter and Instagram.