Page 67 - DCAP407_DATA_STRUCTURE

Data Structure

invalid addresses might cause the system to crash. Pointers used incorrectly can cause bugs and is
difficult to identify.
4.1 Fundamentals of Pointers

The address which locates a variable within the memory is a reference to that variable and can be
obtained by preceding the variable name with an ampersand (&) or the reference operator.

x = & a;

This would assign the address of a to x. Since, & is a reference operator, it stores the address of the
memory and not the content of the variable.

a= 30;
b= a;
x= &a;
Here, b will contain the value of a, whereas x will contain the address of a.
Pointer can be declared as:

type * variablename;
Here, type is the data types of the value like int, char, and float that the pointer points to.

int *a;
char *name;
float *username;
*variablename is used to point to a value that the pointer will point.
An asterisk (*) acts as a dereference operator.

void main ()
{
int iv, fv;
int * m;
m= & iv;
*m= 5;
m = &fv;
*m= 10;
printf( “ Initial value is %d\n “, &fv;)
printf( “ Final value is %d\n”, &sv;)
}
Output:
Initial value is 5
Final value is 10
In this example:
1. First, the address of iv is assigned to m using the reference operator (&).
2. Then, the value 5 is assigned to the memory location pointed by m because
at this moment, m is pointing to the location of iv, which modifies the value
of iv.
3. Then, the address of fv is assigned to m using the reference operator (&).
4. Finally, the value 10 is assigned to the memory location pointed to by m,
i.e., fv, using the dereference operator (*).

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