Pointers in C : MCQs & PYQs with Explanation

Option D

The expression *(arr+3) accesses the 4th element of the array (4). Adding 65 gives 69. Since %c is used, ASCII 69 is printed, which is E.

Option A

int *ptr; declares a pointer to an integer.
char *ptr; declares a pointer to a character.
float *ptr; declare a pointer to a float.
int **ptr; declares pointer to a int * and so on.

Option B

The expression is interpreted as ++(*ptr). Here, dereference happens first and the increment is applied to the value stored at that memory location. The pointer itself does not change, only the data it points to is incremented.

Option B

On a 64-bit system, pointers are typically 8 bytes, regardless of the data type they point to.

Option D

In C language, a pointer that is declared but not initialized with any valid address is called a Wild Pointer. Such pointers contain garbage values and may point to any random memory location, which can cause unpredictable behavior or crashes.
Dangling Pointer: It points to a memory location that has already been freed or deleted.
NULL Pointer: It is a pointer that is explicitly assigned NULL i.e., it points to nothing.
Void Pointer: It is a generic pointer that can hold the address of any data type.
For more about Pointer and Void Pointer.

Option C

In this program, a character array "LAKEVIEW" is stored, and pointer p points to the beginning of the string. Each character has an index position such as L(0), A(1), K(2), E(3), V(4), I(5), E(6), W(7).
The expression p+p[3]-p[1] uses pointer arithmetic. Here, p[3] is 'E' whose ASCII value is 69, and p[1] is 'A' whose ASCII value is 65. So the expression becomes p+(69-65) = p+4.
This means the pointer now points to index 4, which is character 'V'. When printf("%s", p+4) is executed, it prints the string starting from that position, resulting in "VIEW".

Option B

Postfix ++ has higher precedence than *, so increment is applied to the pointer first in parsing. 
However, because it is postfix, the current pointer value is used for dereferencing and then the pointer is incremented. Hence, value is accessed first and pointer moves afterward.

Option A

A pointer stores the address of a variable, and using the dereference operator *, we can access or modify the value stored at that address.
Here, the variable a is initialized with value 5. Then a pointer ptr is declared and assigned the address of a using ptr=&a;. This means ptr now points to a.
In given statement *ptr=*ptr*3, the *ptr accesses the value of a. So, this statement multiplies the current value of a by 3, i.e., 5*3=15 and stores the result back into a itself.
Finally, the printf statement prints the value of a, which is now 15.

Option A

This question involves pointers and operator precedence in C, so careful step-by-step evaluation is required. Initially, the values are a=2 and b=5. The function is called as tchange(&a, &b), so inside the function, pointer b refers to variable a, and pointer a refers to variable b.
First, the statement *a += *a is executed. Since a points to b, this updates b as 5+5 = 10. Next, *b *= *a is executed. Here, b points to a and *a is 10, so a becomes 2*10 = 20.
Now, the statement *a++ = ++*b is evaluated. The expression ++*b increments the value of a to 21. Then *a++ assigns this value to b, and afterward the pointer moves. So now both a and b become 21.
Finally, in the statement *--b = *--a, both pointers are decremented, but they still refer to the same updated variables. This does not change the values further.

Option C

In C, the name of an array represents the base address of the array. When we write ptr=a;, the pointer ptr points to the first element of the array, i.e., a[0].
The ptr+1 moves the pointer to the next integer location. So ptr+1 points to the second element of the array, which is a[1].
The expression *(ptr+1) first moves the pointer ptr to the next memory location, i.e., a[1]. After moving to this position, the * operator (Dereference Operator) is applied, which retrieves the value stored at that memory location, i.e., 2.