Address of a variable in c

Address of a variable in c :

Location in a memory where a variable stores its data or value is known as address of variable. To know address of any variable c has provided a special unary operator & which is known as dereferencing operator or address operator. It operator is only used with variables not with the constant. For example:

#include<stdio.h>

int main(){

    int a=5;

    printf("Address of variable a is: %d",&a);

    return 0;

}

We cannot write: &&a, because:

&&a=& (&a) =& (address of variable a) =& (a constant number)

And we cannot use address operator with constant.

Important points about address of variables in c:

(1)Address of any variable in c is an unsigned integer. It cannot be a negative number. So in printf statement we should use %u instead of %d, to print the address of any variable.

%d: It is used to print signed decimal number.

%u: It is used to print unsigned decimal number.

Since, if the address of any variable will beyond the range of signed short int it will print a cyclic value.

(2)Address of any variable must be within the range 0000 to FFFF in hexadecimal number format or 0 to 65535 i.e. range of unsigned short int in c. To print the address of any variable in hexadecimal number format by printf function we should use %x or %X.

%x: To print a number in hexadecimal format using 0 to 9 and a, b, c, d, e, f.

%X: To print a number in hexadecimal format using 0 to 9 and A, B, C, D, E, F.

(3)A programmer cannot know at which address a variable will store the data. It is decided by compiler or operating system.

(4)Any two variables in c cannot have same physical address.

(5)Address of any variable reserve two bytes of memory spaces.

(6) Address of any variable in c is not integer type so to assign an address to a integral variable we have to type cast the address. For example:

#include<stdio.h>

int main(){

    int a=100;

    unsigned int b=(unsigned)&b;

    printf("%u",b);

    return 0;

}

Address arithmetic in c:

(1) We can subtract address of any two variables.  For example:

#include<stdio.h>

int main(){

    int a;

    int b;

    printf("%d",&b-&a);

    return 0;

}

(2)We cannot add, multiply, divide two addresses.

(3) we can add or subtract a integer number with address.

(3)Other operators which can be used with addresses are:

(a)Negation operator:!

(b)Size operator: sizeof

(c)Type casting operator: (Type)

(e) Dereferencing operator: *

(f)Logical operator: &&, ||

Example:

#include<stdio.h>

int main(){

    int a=12;

    printf("%d",!&a);

    printf("%d",sizeof(&a));

    printf("%d",(int)&a);

    printf("%d",*&a);

    printf("%d  %d %d %d",&a&&&b,&a&&b,&a||&b,&a||b);

    return 0;

}