Data Structures, Algorithms, Programming Concepts (C/C++/Python/Java), OOP & Web Development (Part 4)

Question 1

Which storage class keyword in C is used to declare a global variable or function that is defined in a different source file?

Accepted Answer

extern

Answer

static

Answer

register

Answer

auto

Question 2

Which JavaScript method displays a modal popup dialog box with a specified message and an "OK" button?

Accepted Answer

alert()

Answer

prompt()

Answer

confirm()

Answer

message()

Question 3

In modern JavaScript (ES6+), what is the difference between `let` and `const` variable declarations?

Accepted Answer

`let` declares a block-scoped variable that CAN be reassigned; `const` declares a block-scoped variable that CANNOT be reassigned after initialization

Answer

`const` variables can only hold numbers

Answer

`let` is global only; `const` is local only

Answer

`const` variables expire after 1 hour

Question 4

Which of the following is a semantic layout element introduced in HTML5 to replace generic `

` containers for better document structure and SEO?

Accepted Answer

Answer

Answer

Answer

Question 5

Which HTML tag is used to define an individual data cell within a table row?

Accepted Answer

<td>

Answer

<tr>

Answer

<th>

Answer

<cell>

Question 6

What is the correct syntax for writing comments in an HTML document?

Accepted Answer

Answer

// This is a comment

Answer

/* This is a comment */

Answer

# This is a comment

Question 7

If `int *ptr;` is declared on a 64-bit system where integers are 4 bytes, what is the effect of executing `ptr = ptr + 1;`?

Accepted Answer

The memory address stored in `ptr` increases by 4 bytes (advancing to the next integer memory location)

Answer

The memory address increases by 1 byte

Answer

The value pointed to by `ptr` increases by 1

Answer

It throws a compiler error

Question 8

What is a "Dangling Pointer" in C and C++?

Accepted Answer

A pointer that continues to hold the memory address of a heap block that has already been deallocated/freed via `free()` or `delete`

Answer

A pointer initialized to NULL

Answer

A pointer that points to a function

Answer

A pointer stored in a CPU register

Question 9

What is a "Void Pointer" (`void *ptr`) in C?

Accepted Answer

A generic pointer that can hold the memory address of ANY data type, but must be explicitly typecast before dereferencing

Answer

A pointer that always points to address 0x0

Answer

A pointer that cannot be modified

Answer

A pointer used exclusively in void functions

Question 10

What is the key functional difference between `malloc()` and `calloc()` in C standard library `<stdlib.h>`?

Accepted Answer

`malloc()` allocates uninitialized memory containing garbage values; `calloc()` allocates memory and automatically initializes every allocated byte to zero (0)

Answer

`calloc()` allocates memory on the stack; `malloc()` allocates on the heap

Answer

`malloc()` takes two arguments; `calloc()` takes one

Answer

`calloc()` cannot be freed

Question 11

What occurs when a program continuously allocates heap memory using `malloc()` without ever deallocating it using `free()`?

Accepted Answer

A Memory Leak occurs, causing the program's RAM usage to grow continuously until system memory is exhausted

Answer

The CPU automatically deletes the old variables

Answer

The program runs faster over time

Answer

The compiler creates a backup copy on disk

Question 12

What is the defining behavior of a local variable declared with the `static` keyword inside a C function (e.g. `static int count = 0;`)?

Accepted Answer

It is initialized only ONCE at program startup and retains its value between successive function calls for the entire lifetime of the program

Answer

It is re-initialized to 0 on every function call

Answer

It is stored in the CPU register

Answer

It can be accessed by any other file

Question 13

What is the fundamental memory difference between a `struct` and a `union` in C/C++?

Accepted Answer

In a `struct`, every member has its own independent memory location (total size >= sum of member sizes); in a `union`, all members share the exact same overlapping memory location (size = size of the largest member)

Answer

A `union` is stored on disk; a `struct` is in RAM

Answer

A `struct` can hold only numbers; a `union` holds only text

Answer

Unions cannot contain pointers

Question 14

On a 32-bit architecture with 4-byte word alignment, what is the total size in bytes of `struct Example { char a; int b; char c; };`?

Accepted Answer

12 bytes (due to structure padding bytes inserted for word alignment)

Answer

6 bytes

Answer

4 bytes

Answer

8 bytes

Question 15

In C and C++, which pointer expression is strictly equivalent to the array indexing expression `arr[i]`?

Accepted Answer

*(arr + i)

Answer

&arr + i

Answer

*arr + i

Answer

arr + *i