Interview Questions
- Why is a & operator used in relation to a Pointer?
- Why is a * operator used in relation to a Pointer?
- How are arrays and pointers related?
- Can you change the address pointed to by an array variable?
- What are Character Pointers?
- What is the result of this program?
Why is a & operator used in relation to a Pointer?
The unary operator & gives the address of an object. In the below example, pi = &i is read as pi is the address of i.
#include <stdio.h>
int main()
{
int i;
int *pi;
pi = &i; //Read as "address of" i.
}
Why is a * operator used in relation to a Pointer?
The unary operator * is the indirection or dereferencing operator; In the below example, j = *pi. This is read as (j is the “value at” pi).
#include <stdio.h>
int main()
{
int i = 10;
int *pi;
int j;
pi = &i; //Read as "address of" i.
j = *pi; // Read as "value at" pi.
}
How are arrays and pointers related?
An array variable stores the address of where the first element(index 0) of the array is stored. Hence an array variable is actually a pointer. In the above example marks is similar to a pointer.
Program below shows the different pointer operations that can be done on an array.
#include <stdio.h>
int main()
{
int marks[] = {35,45,67};
printf("%d\n",*marks);//35
printf("%d\n",*(marks+1));//45
printf("%d\n",*(marks+2));//67
printf("%p\n",marks);//0x7fff57a3baac
}
Can you change the address pointed to by an array variable?
No. That’s actually one of the few differences between a normal pointer and an array. The value of a variable or expression of type array is the address of element zero of the array. An array name is not a variable; constructions like marks=pmarks and marks++ are illegal.
#include <stdio.h>
int main()
{
int marks2 = {96,97,98};
int marks[] = {35,45,67};
int *pmarks;
pmarks = marks2;
marks = pmarks; //Not Allowed : Compilation Error
}
What are Character Pointers?
Below program shows an example of character pointer.
#include <stdio.h>
int main()
{
char* text = "Something";
}
What is the result of this program?
#include <stdio.h>
void swap(int *pi, int *pj) //Definition of Function
{
int temp = *pi;
*pi = *pj;
*pj = temp;
}
int main()
{
int a=5, b=6;
swap(&a,&b);
printf("a:%d,b:%d",a,b);//a:6,b:5a
}
In the program above, the values a and b are swapped. The address of the variables a and b are passed to the function. So, the function modifies the original values.
