Computer Knowledge - MCQ Practice Questions

Step 1: x=5. Step 2: ++x makes x=6 (pre-increment, used immediately). Step 3: y = 6 + x++ = 6 + 6 = 12. Step 4: x++ increments x to 7 after use. Final: x=7, y=12.

This is XOR swap algorithm. Step 1: a = 10^20. Step 2: b = (10^20)^20 = 10. Step 3: a = (10^20)^10 = 20. Result: a=20, b=10 (values are swapped).

fgets() is the safe way to read strings including spaces. scanf("%s") stops at whitespace, gets() is deprecated and unsafe due to buffer overflow risks.

A static variable inside a function is initialized only once and retains its value between successive function calls. It has memory allocated in the data segment, not the stack.

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

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

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.

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 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.

Division and multiplication have the same precedence and are evaluated left-to-right. Step 1: $\frac{10}{3}$ = 3 (integer division). Step 2: 3 * 3 = 9. Therefore, the result is 9.

When passing a 2D array to a function, the number of columns must be specified, but the number of rows is optional. Option C is the standard correct syntax.

# Understanding Pre-increment and Post-increment Operators in C

The key to solving this problem is understanding the difference between pre-increment (++x) and post-increment (x++) operators and their evaluation order.

Step 1: Evaluate Pre-increment (++x)

The pre-increment operator increases the variable first, then uses the updated value in the expression.

When ++x is evaluated, x changes from 5 to 6, and the expression uses 6.

Step 2: Evaluate Post-increment (x++) and Addition

The post-increment operator uses the current value in the expression first, then increments the variable afterward.

After the entire expression is evaluated, x++ increments x from 6 to 7, but this happens after the addition is complete.

Step 3: Calculate Final Result

The answer is (B) 12

The ternary operator syntax is: condition ? value_if_true : value_if_false. Option B is the only correctly formatted statement.