The document contains code snippets demonstrating pointer concepts in C like pointer size, pointer arithmetic, passing pointers to functions, static vs extern variables, multiple definitions, etc. It also contains examples showing memory layout of variables in .o files and executable using nm utility. Conflicts due to multiple definitions and resolving them with static keyword is also demonstrated.

2. int *pi;
char *pc;
short int *psi;
printf(“ %d n”,sizeof(pi));
printf(“ %d n”,sizeof(pc));
printf(“ %d n”,sizeof(psi));
int *pi;
char *pc;
short int *psi;
printf(“ %d n”,sizeof(*pi));
printf(“ %d n”,sizeof(*pc));
printf(“ %d n”,sizeof(*psi));

3. int *pi = (int *)2000;
char *pc = (char *)2000;
pi++;
pc++;
printf(“ %u %u “ , pi , pc);

4. int x = 0x1234;
char c = x;
printf(“ %x “ , c);

5. const int x = 10;
1.int * const ptr1 = &x;
2.int const * ptr2 = &x;
3.const int * ptr3 = &x;

6. void update(int *p)
{
*p = *p + 5;
}
int main( )
{
int x = 10;
int *ptr = &x;
update(ptr);
printf(“x = %d “ , x);
}

7. void update(int *p)
{
p = p + 1;
}
int main( )
{
int arr[ ] = {10 , 12 , 25 , 45};
int *ptr = arr;
update(ptr);
printf(“*ptr = %d “ , *ptr);
}

8. void update(int *p)
{
*p = *p + 1;
}
int main( )
{
int arr[ ] = {10 , 12 , 25 , 45};
int *ptr = arr;
update(ptr);
printf(“*ptr = %d “ , *ptr);
}

9. void update(char *str)
{
str = “Devendra”;
}
int main( )
{
char *name = “Nimisha”;
update(name);
printf(“ %s n” , name);
}

10. void update(char *str)
{
str[0] = ‘H’;
}
int main( )
{
char name[ ] = “Nimisha”;
char *ptr = name;
update(ptr);
printf(“ %s n” , name);
}

11. void update(char *str)
{
*++str = ‘a’;
}
int main( )
{
char name[ ] = “Nimisha”;
char *ptr = name;
update(ptr);
printf(“ %s n” , name);
}

12. int main( )
{
char names[]
[10]={“OBAMA”,”PUTIN”,”MODI”,”CAMEROON”};
printf(“ %__ “ , *(names + 2) + 3);
printf(“ %__ “ , **(names + 2) + 3);
}

13. int main( )
{
char names[][10]={“OBAMA”,”PUTIN”,”MODI”,”CAMEROON”};
1. printf(“ %s “ , *(++names));
2. printf(“ %s “ , ++*(names));
3. printf(“ %c “ , ++**(names));
}

14. int main( )
{
char *names[10]={“OBAMA”,”PUTIN”,”MODI”,”CAMEROON”};
1. printf(“ %s “ , *(++names));
2. printf(“ %s “ , ++*(names));
3. printf(“ %c “ , ++**(names));
}

15. struct Student
{
int id;
char name[20];
};
int main( )
{
struct Student s1 = {1 , “Ayushi”};
struct Student s2 = {2 , “Ayushi”};
if(s1.name == s2.name)
printf(“Equal”);
else
printf(“Not Equal”);
}

16. char *names[ ] = {“Nimisha”,”Devender”,”Vikram”,”Balwant”};
printf(“ %d “ , sizeof(names));
printf(“ %d “ , sizeof(names[0]));
char names[ ][10] = {“Nimisha”,”Devender”,”Vikram”,”Balwant”};
printf(“ %d “ , sizeof(names));
printf(“ %d “ , sizeof(names[0]));

17. void display( char *names[ ])
{
printf(“Display : %d n “ , sizeof(names));
}
int main( )
{
char *names[ ] = {“Nimisha”,”Devender”,”Vikram”,”Balwant”};
printf(“Main : %d n“ , sizeof(names));
display( names );
}

18. static int x = 5;
int main( )
{
int x;
printf(“x = %d n”,x);
}

19. static int x = 5;
int main( )
{
extern int x;
printf(“x = %d n”,x);
}

20. int a = 5;
int b;
static int c = 7;
static int d;
int main( )
{
}
• Mention the memory segments of
variables after compiling (.o file) and
after linking (a.out)
• What is the difference between a
and c.
• Use nm utility to view the memory
segments
$gcc –c file.c
$nm file.o
$gcc file.c
$nm ./a.out

21. void func( );
int x;
int main( )
{
x = 5;
func( );
printf(“x = %d “ , x);
}
int x;
void func( )
{
x = 10;
}

22. [sikander@localhost ~]$ gcc -c f1.c
[sikander@localhost ~]$ gcc -c f2.c
[sikander@localhost ~]$ nm f1.o
U func
00000000 T main
U printf
00000004 C x
[sikander@localhost ~]$ nm f2.o
00000000 T func
00000004 C x
[sikander@localhost ~]$ gcc f1.o f2.o
[sikander@localhost ~]$ nm a.out
080495ac B x

23. void func( );
int x = 5;
int main( )
{
func( );
printf(“x = %d “ , x);
}
int x = 10;
void func( )
{
x++;
}

24.  [sikander@localhost ~]$ gcc -c f1.c
 [sikander@localhost ~]$ gcc -c f2.c
 [sikander@localhost ~]$ nm f1.o
 00000000 D x
 [sikander@localhost ~]$ nm f2.o
 00000000 D x
 [sikander@localhost ~]$ gcc f1.o f2.o
 f2.o(.data+0x0): multiple definition of `x'
 f1.o(.data+0x0): first defined here
 collect2: ld returned 1 exit status

25. C C
B
C D
D
D D
Multiple Definition
d d
No Conflict, two different variables
b b
No Conflict, two different variables
d b
No Conflict, two different variables
b d
No Conflict, two different variables
b D
No Conflict, two different variables

26. int x ; //C
int main( )
{
printf(“Main &x= %p” , &x);
printf(“x = %d n”, x);
func( );
}
int x ; //C
void func( )
{
printf(“Func &x= %p” , &x);
printf(“x = %d n”, x);
}
int x ; //C
int main( )
{
printf(“Main &x= %p” , &x);
printf(“x = %d n”, x);
func( );
}
int x = 5 ; //D
void func( )
{
printf(“Func &x= %p” , &x);
printf(“x = %d n”, x);
}

27. void func( );
int x = 5; //D
int main( )
{
printf(“Main &x= %p” , &x);
printf(“x = %d n”, x);
func( );
}
int x = 10; //D
void func( )
{
printf(“Func &x= %p” , &x);
printf(“x = %d n”, x);
}
void func( );
static int x = 5; //d
int main( )
{
printf(“Main &x= %p” , &x);
printf(“x = %d n”, x);
func( );
}
int x = 10; //D
void func( )
{
printf(“Func &x= %p” , &x);
printf(“x = %d n”, x);
}

28. const int x = 10; //Read Only
int main( )
{
const int y = 5; //Stack
}

29. const int x = 10; //Read Only
int main( )
{
const int y = 5; //Stack
printf(“Enter the value for local const variable : “);
scanf(“ %d”,&y);
printf(“Local Const = %d n” , y);
printf(“Enter the value for global const variable : “);
scanf(“ %d”,&x);
printf(“Global Const = %d n”,x);
}
[sikander@localhost ~]$ ./a.out
Enter the value for local const variable : 89
Local Const = 89
Enter the value for global const variable : 6
Segmentation fault

30.  [sikander@localhost ~]$ nm f1.o
 00000000 t display
 0000000a T main
 00000005 T print
static void display()
{
}
void print()
{
}
int main( )
{
display( );
print( );
}