B CompE Bachelor of Computer Engineering Bachelor of Computer Engineering C Language 4

Question 1

In C, what is undefined behavior?

Accepted Answer

Code whose behavior is not specified by the C standard and may produce any result

Answer

Undefined behavior (UB) means the C standard imposes no requirements on what the program does, so compilers may produce any output, including seemingly correct results.

Question 2

Which of the following is a correct way to swap two integers in C without a temporary variable using XOR?

Accepted Answer

a = a ^ b; b = a ^ b; a = a ^ b;

Answer

The sequence `a^=b; b^=a; a^=b;` (written out fully) correctly swaps `a` and `b` using XOR without a temporary variable.

Question 3

What is the difference between `struct` and `union` in C?

Accepted Answer

A `struct` stores members sequentially with individual storage; a `union` shares the same memory for all members

Answer

In a `struct`, each member has its own storage; in a `union`, all members share the same memory location, sized to the largest member.

Question 4

What is the output of: `int x = 10; printf("%d", x++);`?

Accepted Answer

10

Answer

The post-increment operator `x++` evaluates to the current value of `x` (10) before incrementing, so `printf` prints 10.

Question 5

In C, which header file must be included to use `assert()`?

Accepted Answer

<assert.h>

Answer

The `assert()` macro is declared in `<assert.h>` and aborts the program with a diagnostic message if its argument evaluates to false.

B CompE Bachelor of Computer Engineering Practice Test

B CompE Bachelor of Computer Engineering Practice Test

B CompE Bachelor of Computer Engineering Bachelor of Computer Engineering C Language 4