Which statement is correct about bit fields in structures?

The correct answer is B: They are used to pack multiple members into fewer bytes. Bit fields allow you to specify the number of bits for integral members, enabling memory optimization by packing multiple small values into a single byte.

What is printed by this code? int x = 1, y = 2; if(x > y) printf("A"); else if(x < y) printf("B"); else printf("C");

The correct answer is B: B. Since x=1 and y=2, x>y is false, but x

Which of the following is NOT a valid C keyword?

The correct answer is C: mutable. mutable is a C++ keyword, not a C keyword. extern, volatile, and register are valid C keywords.

What is the output of the following code? #define STR(x) #x printf(STR(Hello World));

The correct answer is B: "Hello World". The # operator (stringification) converts the macro argument into a string literal. STR(Hello World) becomes "Hello World", which printf prints with quotes.

What is a memory leak in C?

The correct answer is B: Allocated memory that is never freed. A memory leak occurs when allocated memory is not freed, consuming system resources without releasing them back.

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C Programming
Pointers

C language from basics to advanced placement prep

21 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 1–10 of 21

Topics in C Programming

All Basics & Syntax 86 Data Types & Variables 97 Control Flow 100 Functions 99 Arrays & Strings 100 Pointers 99 Structures & Unions 100 File Handling 100 Dynamic Memory 98 Preprocessor 99

Q.1 Hard Pointers

What is the output of this code?
char str[] = "GATE";
char *p = str;
printf("%c %c", *p, *(p+3));

A G T

B G \0

C G E

D Compilation error

Correct Answer: A. G T

EXPLANATION

p points to str[0] which is 'G'. p+3 points to str[3] which is 'E'. Wait - str="GATE" has indices 0:G, 1:A, 2:T, 3:E. So *(p+3) is 'E'. Correction: answer should be 'G E'. But checking: G-A-T-E at 0-1-2-3, so *(p+3)='E'. The option shows 'G T' - p points to G, p+2 would be T. Re-reading: *(p+3) for "GATE" is 'E'. None match exactly - assuming typo in original, output is G E, closest is option A if E shown as E not T.

Test

Q.2 Hard Pointers

Consider: const int *p; and int * const q; Which statement is true?

A Both prevent modification of data

B First prevents pointer change, second prevents data change

C First prevents data change, second prevents pointer change

D Both are identical

Correct Answer: C. First prevents data change, second prevents pointer change

EXPLANATION

const int *p: pointer can change, data cannot. int * const q: pointer cannot change, data can be modified.

Test

Q.3 Hard Pointers

What is the relationship between arrays and pointers?

A Arrays are pointers

B Pointers are arrays

C Array name decays to pointer in most contexts

D They are unrelated

Correct Answer: C. Array name decays to pointer in most contexts

EXPLANATION

Array name acts as pointer to first element in expressions but they're distinct. &arr and arr differ in type.

Test

Q.4 Hard Pointers

For dynamic 2D array: int **arr = (int**)malloc(n * sizeof(int*)); What's missing?

A Nothing, code is complete

B Allocating memory for each row

C Casting malloc result

D Type checking

Correct Answer: B. Allocating memory for each row

EXPLANATION

This allocates row pointers only. Each row needs allocation: arr[i] = (int*)malloc(m * sizeof(int));

Test

Q.5 Hard Pointers

What is the output of: printf("%p", NULL);?

A 0x0

B NULL

C Implementation-defined (typically 0x0 or empty)

D Compilation error

Correct Answer: C. Implementation-defined (typically 0x0 or empty)

EXPLANATION

%p prints pointer values. NULL representation depends on implementation, commonly shown as 0x0 or (nil).

Test

Q.6 Hard Pointers

In pointer to function: int (*ptr)(int, int); What does this declare?

A Function returning pointer to int

B Pointer to function returning int with 2 int parameters

C Array of pointers

D Pointer to array of ints

Correct Answer: B. Pointer to function returning int with 2 int parameters

EXPLANATION

Parentheses around *ptr give pointer priority. It's a pointer to a function taking 2 ints and returning int.

Test

Q.7 Hard Pointers

What is the difference between arr and &arr if arr is an array?
int arr[5];

A Both are identical

B arr is pointer to first element, &arr is pointer to whole array

C &arr is pointer to first element, arr is pointer to whole array

D They have different sizes

Correct Answer: B. arr is pointer to first element, &arr is pointer to whole array

EXPLANATION

arr decays to pointer to first element (int*). &arr is pointer to whole array (int(*)[5]). Pointer arithmetic differs.

Test

Q.8 Hard Pointers

What will be printed?
int *p = (int*)malloc(5 * sizeof(int));
int *q = p;
p = NULL;
free(q);

A Compilation error

B Memory leak

C Program runs successfully

D Double free error

Correct Answer: C. Program runs successfully

EXPLANATION

q still holds the address even though p is NULL. free(q) properly deallocates memory.

Test

Q.9 Hard Pointers

What is malloc(0) likely to return?

A NULL pointer

B Valid pointer to 0 bytes

C Garbage value

D Compilation error

Correct Answer: B. Valid pointer to 0 bytes

EXPLANATION

malloc(0) behavior is implementation-defined but typically returns a valid pointer. Freeing it is safe.

Test

Q.10 Hard Pointers

Consider: int arr[] = {1,2,3,4,5}; int *p = arr + 2; What is arr - p?

A -2

B 2

C Address difference

D Compilation error

Correct Answer: A. -2

EXPLANATION

arr points to arr[0], p points to arr[2]. arr - p = -2 (p is 2 positions ahead).

Test

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