C puzzles

1. What is the output of following C program ?

int main()
{
func(5);
return 0;
}
func(int a)
{
int a;
a=10;
printf("%d",a);
}

=> This will end up in error.

error: 'a' redeclared as different kind of symbol

Reason: As int a is a local variable it will be stored in stack, when once 

again a is re-declared it will thrown an error.

2.What is the output of following C program ?

int a=5;
int main()
{
func(5);
return 0;
}
func(int a)
{
a=10;
printf("%d",a);
}

Output => 10

Reason: In statement int a =5; a will be stored in data segment of memory, 

where as int a in func(int a) will be stored in stack. So no redeclaration 

scenario like earlier case.

3. In the below program 'a' is a global variable. So it can be accessed by 

all functions.Is there any way to restrict the access of variable 'a' from 

func3() ?

int a;
int main()
{
func1();

func2();

func3();
return 0;
}
func1()
{

}
func2()
{

}
func3()
{

}

Answer => Yes. Look into the previous example. By declaring 'a' inside func3() 

we can restrict access to global variable 'a'

int a;
int main()
{
func1();func2();func3();
return 0;
}
func1()
{

}
func2()
{

}
func3()
{
int a;
}

4. What is the output of the following two programs?

int main()
{
char *p = NULL;
printf("%d %d",p,p++);
return 0;
}

Output => 0 1

Reason: NULL is always stored in the zeroth location. Increment pointer of char type

will shift to position 1 as char takes 1 byte.

int main()
{ 

int *p = NULL;
printf("%d %d",p,p++);
return 0;
}

Output => 0 4

Reason: NULL is always stored in the zeroth location. Increment pointer of int type

will shift to position 4 as int takes 4 byte. 

5. What is the prototype of malloc and free ?

Answer =>

void *malloc(size_t size); 
void free(void *ptr);  

size_t is of unsigned type.