Computer Knowledge - MCQ Practice Questions

Both are valid syntax. Option A declares an anonymous structure with immediate variable instantiation. Option B declares a named structure type that can be used later to create variables.

The volatile keyword tells the compiler that a variable's value may change unexpectedly (e.g., due to hardware, interrupts, or other threads), preventing compiler optimizations that assume the value doesn't change.

When ptr points to the array arr, ptr[1] is equivalent to *(ptr+1), which accesses the second element of the array, which is 2.

The increment (++) and decrement (--) operators have the highest precedence among all operators in C, followed by unary operators, then multiplicative, additive, and so on.

The 'break' statement is used to exit or terminate a loop or switch statement immediately. It transfers control to the statement following the loop or switch.

The while loop starts with i=0. It prints 0, then increments i to 1, prints 1, increments to 2, prints 2, increments to 3, and the condition i<3 becomes false, so the loop terminates. Output: 0 1 2

The free() function is used to deallocate memory that was previously allocated using malloc(), calloc(), or realloc(). This prevents memory leaks.

This declaration creates a pointer to an integer and initializes it to NULL, which means it doesn't point to any valid memory address. This is a safe initialization practice.

Since both 5 and 2 are integers, integer division is performed: $\frac{5}{2}$ = 2. The %f format specifier then prints this integer value (2) as a floating-point number: 2.000000

A 2D array in C is declared using the syntax: datatype arrayName[rows][columns]. So 'int arr[3][4];' creates a 2D array with 3 rows and 4 columns.

The sizeof() operator returns the size in bytes of a data type or variable. For example, sizeof(int) typically returns 4 on most 32-bit systems.

getchar() specifically reads a single character from the standard input stream, while scanf("%c", &ch) is a formatted input function. getchar() is more straightforward for reading single characters.

The array has 5 rows and 3 columns, so total elements = 5 × 3 = 15 elements. Each int typically occupies 4 bytes. Total memory = 15 × 4 = 60 bytes (assuming sizeof(int) = 4 bytes on most systems).

In C, the modulus operator (%) returns a remainder that has the same sign as the dividend. For example, -7 % 3 = -1 (not 2), because -7 is the dividend and it's negative.

A pointer is a variable that stores the memory address of another variable. You can access the value at that address using the dereference operator (*), and pointers can point to any data type.

Both 'const int x = 10;' and 'int const x = 10;' are valid ways to declare a constant in C. The const keyword can be placed before or after the type specifier, and both have the same meaning.

The do-while loop executes the body at least once before checking the condition. The syntax is: do { statements; } while(condition);. In contrast, while and for loops check the condition first.

Variables declared inside a block (enclosed in curly braces) have local or block scope. They are accessible only within that block and cease to exist once the block execution is complete.

The loop executes for i=0, i=1, and i=2. When i=3, the break statement is encountered, which immediately terminates the loop. Therefore, the loop executes exactly 3 times.

All three methods are correct ways to initialize a pointer to NULL. 0, NULL, and (void*)0 all represent a null pointer. NULL is typically a macro defined as 0 or ((void*)0) in the standard library.