B CompE Bachelor of Computer Engineering Bachelor of Computer Engineering C Language 3

Question 1

What is the purpose of the `#pragma once` directive in C header files?

Accepted Answer

Prevents the header from being included more than once per compilation unit

Answer

`#pragma once` is a non-standard but widely supported guard that ensures a header is included only once during compilation.

Question 2

In C, what is the difference between `calloc` and `malloc`?

Accepted Answer

`calloc` zero-initializes the allocated memory; `malloc` does not

Answer

`calloc(n, size)` allocates `n` elements of `size` bytes each and zero-initializes the block, while `malloc` leaves memory uninitialized.

Question 3

Which C operator is used to access a struct member through a pointer?

Accepted Answer

->

Answer

The `->` operator dereferences a pointer and accesses the named member in one step, equivalent to `(*ptr).member`.

Question 4

What does `strncpy(dest, src, n)` do differently from `strcpy`?

Accepted Answer

It copies at most n bytes, padding with null bytes if src is shorter

Answer

`strncpy` copies at most `n` characters from `src` to `dest` and pads with null bytes if `src` is shorter than `n`, but may not null-terminate if `src` is longer.

Question 5

In C, what is the value of `NULL`?

Accepted Answer

Implementation-defined but guaranteed to compare equal to a null pointer

Answer

The C standard defines `NULL` as an implementation-defined null pointer constant that compares equal to a null pointer; it is typically defined as `0` or `(void*)0`.

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 3