Computer Knowledge - MCQ Practice Questions

The correct answer is 6 because q is a pointer to pointer that points to p, which points to x. When we dereference q, we get the value of x (which is 5), and then adding 1 gives us 6, which is printed. The key concept here is understanding pointer dereferencing: a single asterisk dereferences one level, so double asterisks dereference two levels, bringing us from q to p to the actual value stored in x. Any other answer would be incorrect because it would either misunderstand the double dereferencing operation or incorrectly interpret what value is being accessed—for instance, if someone only dereferenced once or forgot to add 1, they would get a different result.

The output is 5 and 8 because sizeof(arr) returns 5 bytes (4 characters plus 1 null terminator in the string "GATE"), while sizeof(p) returns 8 bytes on a 64-bit system since p is a pointer variable and pointers occupy 8 bytes in 64-bit architecture. The key concept is that sizeof() behaves differently for arrays versus pointers: when applied to an array, it returns the total memory allocated for the entire array, but when applied to a pointer, it only returns the size of the pointer itself, not what it points to. Other options would be incorrect because they either miscalculate the array size by forgetting the null terminator, use incorrect pointer sizes (like 4 bytes for 32-bit systems), or confuse the size of the array with the size of the pointer variable.

Hash Tables achieve O(1) average-case time complexity for both insertion and search operations when using a well-designed hash function that minimizes collisions and maintains a good load factor.

Deletion also operates in O(1) average time.

However, in worst-case scenarios with poor hash functions or high collision rates, these operations can degrade to O(n).

The key to performance is maintaining low collision rates through techniques like chaining or open addressing.

A Heap (either Min-Heap or Max-Heap) is the optimal data structure for implementing priority queues with O(log n) insertion and deletion time complexity.

In a Max-Heap, the element with the highest priority is always at the root, enabling efficient extraction of the maximum element.

Arrays and Linked Lists would require O(n) time for priority-based operations, while Graphs are unsuitable for this purpose.

Heaps are fundamental in algorithms like Dijkstra's and Prim's for finding shortest paths.

This code exhibits undefined behavior because x is modified twice between sequence points without an intervening sequence point. The result depends on the compiler's implementation.

scanf() reads formatted input based on format specifiers and stops at whitespace. gets() reads a string until a newline is encountered. Note: gets() is deprecated due to buffer overflow vulnerabilities.

Both A and B are correct. Option A uses explicit type casting which is optional in C (not in C++). Option B avoids casting. Using sizeof(int) is preferred over hardcoding 4, as int size may vary across systems.

*ptr dereferences the pointer to access the value at the address it points to, which is x = 5. So both *ptr and x print 5.

strcpy() does not perform bounds checking. If the source string is longer than the destination buffer, it will write beyond the buffer boundary, causing a buffer overflow. This is a security vulnerability. Using strncpy() is safer.

ptr points to arr[0]. ptr + 1 points to arr[1]. *(ptr + 1) dereferences to get the value at arr[1] which is 20. Pointer arithmetic adds sizeof(int) to the address for each increment.

A static variable declared inside a function has local scope (visible only within that function) but persists for the entire program lifetime. Its value is retained between function calls and is initialized only once.

Step 1: Evaluate condition x < y → 10 < 20 → true. Step 2: Execute true branch: x++ returns 10, then x becomes 11. Step 3: z = 10. Step 4: printf prints x=11, y=20, z=10.

A pointer is a variable that stores the memory address of another variable. It is declared using the * symbol.

malloc() (memory allocation) allocates a block of memory dynamically during program execution and returns a pointer to it.

Arrays in C are declared with square brackets containing the size, followed by initialization in curly braces. Option A is the correct syntax.

In C, if a function's return type is not explicitly specified, it defaults to int. However, modern C standards require explicit return type declaration.

The break statement immediately terminates the loop and transfers control to the statement following the loop.

The arrow operator (->) is used to access structure members through a pointer. The dot operator (.) is used for direct access.

#define is a preprocessor directive used to define symbolic constants (macros) and performs text substitution before compilation.

To explicitly declare a function with no parameters in C, use 'void' as the parameter. int func(); is ambiguous in older C standards.