C Programming — Basics & Syntax Questions & Answers

Q.1 Medium Basics & Syntax

What is the output of this code?
#include
int main() {
int a = 5, b = 10;
a = a ^ b;
b = a ^ b;
a = a ^ b;
printf("%d %d", a, b);
return 0;
}

A 5 10

B 10 5

C 0 0

D 10 10

Correct Answer: B. 10 5

EXPLANATION

This is a classic XOR swap algorithm. After three XOR operations, a and b exchange their values. Result: a=10, b=5.

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Q.2 Medium Basics & Syntax

What will be printed by the following code?
#include
int main() {
int arr[5] = {1, 2, 3, 4, 5};
int *p = arr;
printf("%d %d", *(p+2), arr[2]);
return 0;
}

A 3 3

B 2 4

C 4 3

D 3 4

Correct Answer: A. 3 3

EXPLANATION

*(p+2) accesses the element at index 2 (value 3), and arr[2] also accesses index 2 (value 3). Both print 3.

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Q.3 Medium Basics & Syntax

Consider the following code:
int x = 5;
int *ptr = &x;
int **pptr = &ptr;
printf("%d", **pptr);
What is the output?

A 5

B Address of x

C Address of ptr

D Compilation Error

Correct Answer: A. 5

EXPLANATION

pptr is a pointer to pointer. **pptr dereferences twice: first to get ptr, then to get x's value which is 5.

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Q.4 Medium Basics & Syntax

Which of the following about register variables is TRUE?

A They must be initialized

B They are faster to access than normal variables

C They cannot be pointers

D They are stored in RAM

Correct Answer: B. They are faster to access than normal variables

EXPLANATION

register keyword suggests the compiler to store the variable in CPU register for faster access. Modern compilers often ignore this hint. You cannot take address of register variables.

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Q.5 Medium Basics & Syntax

What does the 'volatile' keyword in C indicate?

A Variable value can change unexpectedly

B Variable is constant

C Variable is local

D Variable must be initialized

Correct Answer: A. Variable value can change unexpectedly

EXPLANATION

volatile tells the compiler that a variable's value can change unexpectedly (e.g., in hardware registers or interrupt handlers), so it should not optimize away repeated reads.

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Q.6 Medium Basics & Syntax

What is the output of: printf("%d %d", 10 % 3, 10 / 3);

A 3 3

B 1 3

C 3 1

D 10 10

Correct Answer: B. 1 3

EXPLANATION

10 % 3 = 1 (remainder), 10 / 3 = 3 (integer division). Output is '1 3'.

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Q.7 Medium Basics & Syntax

Which of the following is correct about static variables in C?

A They are destroyed after function returns

B They retain their value between function calls

C They cannot be used in functions

D They are global by default

Correct Answer: B. They retain their value between function calls

EXPLANATION

Static variables retain their value between function calls and are initialized only once. They persist for the lifetime of the program.

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Q.8 Medium Basics & Syntax

What will be the output of: int a = 5; int b = a < 10 ? 20 : 30; printf("%d", b);

A 5

B 10

C 20

D 30

Correct Answer: C. 20

EXPLANATION

This is the ternary operator. Since 5 < 10 is true, b = 20. If false, b would be 30.

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Q.9 Medium Basics & Syntax

What is the purpose of the getchar() function in C?

A Get a string from input

B Get a single character from input

C Get a number from input

D Get a pointer from input

Correct Answer: B. Get a single character from input

EXPLANATION

getchar() reads a single character from standard input and returns it. For strings, fgets() or scanf() is used.

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Q.10 Medium Basics & Syntax

In C99 and later standards, what is the purpose of 'inline' keyword?

A To declare variables inline

B A suggestion to the compiler to inline function calls

C To restrict variable scope

D To allocate memory inline

Correct Answer: B. A suggestion to the compiler to inline function calls

EXPLANATION

'inline' is a hint to the compiler suggesting it should inline the function, though the compiler may ignore it.

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