Computer Knowledge — MCQ Practice Questions & Answers

Question 1

What is the output of the following C code? int x = 5; printf("%d", x++);

Accepted Answer

Correct answer: B. 5 — The post-increment operator (x++) returns the current value of x before incrementing. So printf prints 5, and then x becomes 6.

Answer

A. 6

Answer

C. Compilation error

Answer

D. Undefined behavior

Question 2

Which of the following is the correct syntax to declare a pointer in C?

Accepted Answer

Correct answer: A. int *ptr; — In C, pointers are declared using the asterisk (*) symbol before the variable name. The syntax is 'datatype *pointer_name;'

Answer

B. int& ptr;

Answer

C. int ^ptr;

Answer

D. int @ptr;

Question 3

What will be the size of the following array in bytes? char arr[10];

Accepted Answer

Correct answer: A. 10 bytes — Each char occupies 1 byte in memory. An array of 10 chars will occupy 10 × 1 = 10 bytes.

Answer

B. 20 bytes

Answer

C. 40 bytes

Answer

D. 5 bytes

Question 4

What is the purpose of the 'void' keyword in C?

Accepted Answer

Correct answer: C. Both A and B — void is used in two contexts: (1) as a function return type when a function doesn't return a value, and (2) to declare a generic pointer (void *) that can point to any data type.

Answer

A. To declare a function that returns nothing

Answer

B. To declare a generic pointer

Answer

D. To declare empty variables

Question 5

What is the output of the following C code? int a = 10, b = 20; int c = (a > b) ? a : b; printf("%d", c);

Accepted Answer

Correct answer: B. 20 — The ternary operator (condition ? true_value : false_value) evaluates the condition (a > b). Since 10 is not greater than 20, it returns b which is 20.

Answer

A. 10

Answer

C. Compilation error

Answer

D. 30

Question 6

What does the strlen() function return?

Accepted Answer

Correct answer: B. Number of characters in a string excluding null terminator — strlen() returns the length of a string without counting the null terminator ('\0'). For example, strlen("hello") returns 5, not 6.

Answer

A. Number of characters in a string including null terminator

Answer

C. Size of memory allocated to string

Answer

D. Address of the first character

Question 7

Which header file is required to use the printf() function in C?

Accepted Answer

Correct answer: B. #include — The stdio.h header file contains declarations for standard input/output functions like printf() and scanf().

Answer

A. #include

Answer

C. #include

Answer

D. #include

Question 8

Which of the following is a valid variable name in C?

Accepted Answer

Correct answer: B. _variable — Variable names in C must start with a letter or underscore, not a digit. _variable is valid. '2var' starts with digit, 'var-name' contains hyphen (invalid), 'var name' contains space (invalid).

Answer

A. 2var

Answer

C. var-name

Answer

D. var name

Computer Knowledge - MCQ Practice Questions