Pointer — Part 1 MCQs with Explanations

The 'free' function in C is used to deallocate memory that was previously allocated using functions like malloc , calloc , or realloc . When memory is allocated dynamically , it resides in the heap, and it is the programmer's responsibility to release that memory when it is no longer needed. Using 'free' helps prevent memory leaks by returning the allocated memory back to the system. Option A is incorrect because allocating memory is done using malloc , calloc , or realloc . Option C is incorrect because 'free' does not create new pointers. Option D is incorrect because 'free' does not modify the value of the pointer; it only releases the memory the pointer points to. Therefore, the correct answer is Option B: Deallocate memory .

In the given C program code snippet: void main() { char far *farther, *farthest; printf("%d..%d", sizeof(farther), sizeof(farthest)); } The sizeof operator is used to determine the size, in bytes, of a variable or data type. 1. ** farther ** and ** farthest ** are both pointers of type **char***. In C, the size of a pointer is typically **4 bytes** on a 32-bit system or **8 bytes** on a 64-bit system. Assuming a standard 32-bit architecture, the size of both pointers would be **4 bytes**. 2. Therefore, the output of the printf function will be: - sizeof(farther) = 4 - sizeof(farthest) = 4 The printf statement prints these two sizes, resulting in the output **"4..4"**. Hence, the correct answer is **Option C: 4..4**.

In first sizeof, str1 is a character pointer so it gives you the size of the pointer variable. In second sizeof the name str2 indicates the name of the array whose size is 5 (including the 'null' termination character). The third sizeof is similar to the second one.

Using a pointer variable, without initializing it, will be disastrous, as it will have a garbage value.

int *ptr, p; ptr is declared as a pointer to an integer because of the `*` symbol next to it. This means that `ptr` can hold the address of an integer variable. p is declared as a regular integer variable, not a pointer. The absence of the `*` symbol means that `p` will hold an integer value directly, not an address. Key Points: - ptr : Pointer to integer, can store addresses of integer variables. - p : Regular integer variable, cannot store addresses.

* is a dereference operator & is a reference operator. They can be applied any number of times provided it is meaningful. Here p points to the first character in the string " Hello ". * p dereferences it and so its value is H . Again & references it to an address and * dereferences it to the value H .

char * p = NULL is same as char * q = 0. In both declarations p and q are initialized to null.

p is pointer of type void.

int * : pointer to int int const * : pointer to const int int * const : const pointer to int int const * const : const pointer to const int Now the first const can be on either side of the type so: const int * == int const * const int * const == int const * const So the above declaration is pointer to const int. Which means, we cannot change the value pointed by ptr .

Address of variable a is assigned to the integer pointer ptr . Due to the statement; *ptr += 1; value at address pointing by ptr incremented by 1. As the value at address is changed so variable a also get the updated value.

OPTION 'A' AS CORRECT... THERE ARE SEVERAL DIFFERENT USES OF POINTERS IN C...THEY ARE (1) int *p ; // p is a pointer to an integer quantity (2) int *p[10] ; // p is a 10-element array of pointers to integer quantities (3) int (*p)[10] ; // p is a pointer to a 10-element integer array (4) int *p(void); // p is a function that returns a pointer to an integer quantity (5) int p(char *a); // p is a function that accepts an argument which is a pointer to a character returns an integer quantity (6) int *p(char *a); // p is a function that accepts an argument which is a pointer to a character returns a pointer to an integer quantity. (7) int (*p)(char *a); // p is pointer to a function that accepts an argument which is a pointer to a character returns an integer quantity. (8) int (*p(char *a))[10]; // p is a function that accepts an argument which is a pointer to a character returns a pointer to a 10-element integer array. (9) int p(char (*a)[]); // p is a function that accepts an argument which is a pointer to a character array returns an integer quantity. (10) int p(char *a[]); // p is a function that accepts an argument which is a array of pointers to characters returns an integer quantity (11) int *p(char a[]); // p is a function that accepts an argument which is a character array returns a pointer to an integer quantity (12) int *p(char (*a)[]); // p is a function that accepts an argument which is a pointer to a character array returns a pointer to an integer quantity (13) int *p(char *a[]); // p is a function that accepts an argument which is an array of pointers to characters // returns a pointer to an integer quantity (14) int (*p)(char (*a)[]); // p is pointer to a function that accepts an argument which is a pointer to a character array returns an integer quantity (15) int *(*p)(char (*a)[]); // p is pointer to a function that accepts an argument which is a pointer to a character array returns a pointer to an integer quantity (16) int *(*p)(char *a[]); // p is pointer to a function that accepts an argument which is a array of pointers to characters returns a pointer to an integer quantity (17) int (*p[10])(void); // p is 10-element array of pointers to functions; each function returns an integer quantity (18) int (*p[10])(char a); // p is 10-element array of pointers to functions; each function accepts an argument which is a character and returns an integer quantity (19) int *(*p[10])(char a); // p is 10-element array of pointers to functions; each function accepts an argument which is a character and returns a pointer to an integer quantity (20) int *(*p[10])(char *a); // p is 10-element array of pointers to functions; each function accepts an argument which is a pointer to a character and returns a pointer to an integer

The sizeof () operator gives the number of bytes taken by its operand. p is a character pointer, which needs one byte for storing its value (a character). Hence sizeof (* p ) gives a value of 1. Since it needs two bytes to store the address of the character pointer sizeof ( p ) gives 2.

When subtracting pointers you get the number of elements between those addresses, not the number of bytes.

Every pointer regardless of its type whereas single pointer or pointer to pointer, needs only 2 bytes. Size of pointer and int is 2 bytes in Turbo C compiler on windows 32 bit machine . So size of pointer is compiler specific. But generally most of the compilers are implemented to support 4 byte pointer variable in 32 bit and 8 byte pointer variable in 64 bit machine.

&& is logical AND operator and this operator requires two operands.

After the execution of the program, the value of the first element of the array 'a' will be modified. Let's break down the code step by step: a[0] = 1; : Sets the first element of the array 'a' to 1. a[1] = 2; : Sets the second element of the array 'a' to 2. p = a; : Assigns the address of the first element of the array 'a' to the pointer 'p'. (*p)++; : Increments the value at the memory location pointed to by 'p'. Since 'p' points to the first element of 'a', it increments the value of 'a[0]' . After the execution of the program, the value of a[0] will be 2. Therefore, the correct statement is Option B: a[0] = 2 .

Variable declaration is the correct answer to “In C, what is a pointer primarily used for”. This question is standard in competitive examination syllabi for Pointer.

4 is the correct answer to “What is the result of the expression sizeof(int*) in C, assuming an int pointer on a typical system”. This question is standard in competitive examination syllabi for Pointer.

int *ptr is the correct answer to “In C, how do you declare a pointer variable that can store the address of an integer”. This question is standard in competitive examination syllabi for Pointer.

Member access operator is the correct answer to “What is the purpose of the '->' operator in C when used with pointers”. This question is standard in competitive examination syllabi for Pointer.

Undefined is the correct answer to “In C, what is the value of a pointer variable if it hasn't been assigned any address”. This question is standard in competitive examination syllabi for Pointer.

Value pointed to by ptr is the correct answer to “What is the result of the expression *ptr in C, where ptr is a pointer to an int”. This question is standard in competitive examination syllabi for Pointer.

To store any data type's address is the correct answer to “In C, what is the purpose of the 'void' pointer type (void*)”. This question is standard in competitive examination syllabi for Pointer.

int (*ptr)(int, int) is the correct answer to “How do you declare a pointer to a function that takes two integers and returns an integer in C”. This question is standard in competitive examination syllabi for Pointer.

Move ptr to the next memory location is the correct answer to “What is the result of the expression ptr++ in C, where ptr is a pointer”. This question is standard in competitive examination syllabi for Pointer.

To make the pointer point to a constant value is the correct answer to “In C, what is the purpose of the 'const' keyword when used with a pointer declaration”. This question is standard in competitive examination syllabi for Pointer.

Address of variable is the correct answer to “What is the result of the expression &variable in C, where variable is a variable of type int”. This question is standard in competitive examination syllabi for Pointer.

A pointer to a pointer is the correct answer to “In C, what is a double pointer (int**)”. This question is standard in competitive examination syllabi for Pointer.

Initialize ptr to 0 is the correct answer to “What is the result of the expression ptr = NULL in C, where ptr is a pointer”. This question is standard in competitive examination syllabi for Pointer.

Allocate memory on the heap is the correct answer to “In C, what is the purpose of the 'malloc' function”. This question is standard in competitive examination syllabi for Pointer.

Error is the correct answer to “What is the result of the expression *NULL in C”. This question is standard in competitive examination syllabi for Pointer.

Copy the contents of one memory location to another is the correct answer to “In C, what is the purpose of the 'memcpy' function”. This question is standard in competitive examination syllabi for Pointer.

4 is the correct answer to “What is the result of the expression sizeof(char*) in C, assuming a char pointer on a typical system”. This question is standard in competitive examination syllabi for Pointer.

int* arr[] is the correct answer to “In C, how do you declare an array of pointers to integers”. This question is standard in competitive examination syllabi for Pointer.

A pointer to a constant value is the correct answer to “In C, what is a pointer to a constant value (const int*)”. This question is standard in competitive examination syllabi for Pointer.

A pointer that points to a function is the correct answer to “In C, what is a function pointer”. This question is standard in competitive examination syllabi for Pointer.

Address of the first element in the array is the correct answer to “What is the result of the expression &array[0] in C, where array is an integer array”. This question is standard in competitive examination syllabi for Pointer.

A pointer that points to the address 0 is the correct answer to “In C, what is a null pointer (NULL or 0)”. This question is standard in competitive examination syllabi for Pointer.

Move ptr two memory locations forward is the correct answer to “What is the result of the expression ptr += 2 in C, where ptr is a pointer”. This question is standard in competitive examination syllabi for Pointer.

Allocate memory for an array of variables is the correct answer to “In C, what is the purpose of the 'calloc' function”. This question is standard in competitive examination syllabi for Pointer.