Which header file must be included to use the NULL macro?

The correct answer is D: Any of the above. NULL is defined in multiple standard headers including , , , , and others. Any of these can be included to use NULL.

What will be the output of this recursive function? int fact(int n) { if(n

The correct answer is C: 120. This calculates factorial. fact(5) = 5*4*3*2*1 = 120. Base case n

In C99, which of the following is a valid use of token pasting operator (##)?

The correct answer is D: Both A and B. Both options A and B are valid. The ## operator pastes two tokens together. Whitespace around ## doesn't matter. #define CONCAT(a,b) a##b could be used as CONCAT(var, 1) to create var1.

What happens if a function declared as returning int doesn't contain a return statement?

The correct answer is C: Returns undefined/garbage value. Without an explicit return statement, the function returns whatever value is in the return register, which is undefined behavior.

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C Programming
Arrays & Strings

C language from basics to advanced placement prep

30 Q 10 Topics Take Mock Test

Difficulty: All Easy Medium Hard 21–30 of 30

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.21 Easy Arrays & Strings

What does strlen() function return for the string "C2025"?

A 5

B 6

C 4

D Undefined behavior

Correct Answer: A. 5

EXPLANATION

strlen() counts characters before the null terminator. "C2025" has 5 characters, so strlen returns 5. The null terminator is not counted.

Test

Q.22 Easy Arrays & Strings

What is the time complexity of accessing an element at index 5 in an array?

A O(1) - Constant time

B O(n) - Linear time

C O(log n) - Logarithmic time

D O(n²) - Quadratic time

Correct Answer: A. O(1) - Constant time

EXPLANATION

Array access by index is O(1) because arrays use contiguous memory allocation, allowing direct access via base address + offset calculation.

Test

Q.23 Easy Arrays & Strings

How much memory is allocated for char name[50] declaration?

A 50 bytes

B 49 bytes

C 51 bytes

D Depends on compiler

Correct Answer: A. 50 bytes

EXPLANATION

char name[50] allocates exactly 50 bytes. The null terminator '\0' must fit within this 50-byte allocation.

Test

Q.24 Easy Arrays & Strings

In C, a string is internally represented as:

A An array of characters terminated by '\0'

B An array of integers with length prefix

C A special data type with built-in length

D A pointer to the first character with separate length variable

Correct Answer: A. An array of characters terminated by '\0'

EXPLANATION

In C, strings are null-terminated character arrays. The null character '\0' marks the end of the string.

Test

Q.25 Easy Arrays & Strings

If an integer array arr[10] is declared globally in C, what will be the initial values of its elements?

A All elements initialized to 0

B All elements contain garbage values

C All elements initialized to 1

D Elements are uninitialized until explicitly set

Correct Answer: A. All elements initialized to 0

EXPLANATION

Global arrays in C are automatically initialized to 0 by default. Only local arrays contain garbage values.

Test

Q.26 Easy Arrays & Strings

Consider a 2D array declared as: int matrix[3][4]. How many elements does it have?

A 3

B 4

C 7

D 12

Correct Answer: D. 12

EXPLANATION

A 2D array with dimensions 3x4 has 3*4 = 12 total elements.

Test

Q.27 Easy Arrays & Strings

What does the following code do? strcpy(dest, src);

A Compares two strings

B Copies string src to dest

C Concatenates two strings

D Finds length of string

Correct Answer: B. Copies string src to dest

EXPLANATION

strcpy() copies the contents of the source string to the destination string.

Test

Q.28 Easy Arrays & Strings

Which of the following is NOT a valid string initialization?

A char str[] = "Program";

B char str[10] = {'P','r','o','g'};

C char str[10]; str = "Program";

D char *str = "Program";

Correct Answer: C. char str[10]; str = "Program";

EXPLANATION

Array names are constant pointers and cannot be reassigned. Direct assignment to char array after declaration is invalid.

Test

Q.29 Easy Arrays & Strings

What will be the output of strlen("Hello") in C?

A 4

B 5

C 6

D Error

Correct Answer: B. 5

EXPLANATION

strlen() returns the length of the string excluding the null terminator '\0'. "Hello" has 5 characters.

Test

Q.30 Easy Arrays & Strings

What is the correct way to declare a 1D array of 10 integers in C?

A int arr[10];

B int arr(10);

C int arr{10};

D int [10]arr;

Correct Answer: A. int arr[10];

EXPLANATION

In C, arrays are declared with the syntax: datatype arrayname[size]. Option A follows the correct syntax.

Test

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