Computer Knowledge - MCQ Practice Questions

Both malloc() and calloc() allocate dynamic memory. The key difference is that malloc() allocates uninitialized memory (contains garbage values), while calloc() allocates memory and initializes all bytes to zero. calloc() also takes two arguments (number of elements and size of each element), while malloc() takes one (total bytes needed).

In array notation, arr is a pointer to the first element. *(arr + 3) dereferences the pointer that points to the 4th element (index 3). Since array indexing is 0-based: arr[0]=1, arr[1]=2, arr[2]=3, arr[3]=4. Therefore, *(arr + 3) = 4.

The printf() function is defined in the Standard Input/Output library. Therefore, '#include <stdio.h>' must be included at the beginning of the program to use printf() and other I/O functions like scanf(), getchar(), putchar(), etc.

When p is a pointer to a structure, we cannot use p.x (dot notation) directly. The correct ways are: p->x (arrow operator) or (*p).x (dereference then dot operator). The notation p.x would be used only if p were a structure variable, not a pointer. Therefore, p.x is incorrect when p is a pointer.

3NF removes transitive dependencies where a non-key attribute depends on another non-key attribute. BCNF is stricter but 3NF is the standard answer for eliminating transitive dependencies.

Binary search divides the search space in half with each iteration, resulting in logarithmic time complexity O(log n).

DROP removes the entire table structure and data. DELETE removes only data. TRUNCATE removes data but is faster than DELETE.

Hash collisions occur when two different keys hash to the same table index. Resolution techniques include chaining and open addressing.

Relational databases store structured data in tables. Unstructured data is typically stored in NoSQL or document databases.

ACID properties ensure reliable database transactions: Atomicity (all-or-nothing), Consistency (valid state), Isolation (concurrent independence), Durability (permanent storage).

A heap (binary heap) efficiently implements priority queues with O(log n) insertion and deletion of minimum/maximum elements.

INNER JOIN returns only rows with matches in both tables. LEFT JOIN returns all rows from the left table plus matching rows from the right table.

IaaS provides infrastructure resources (compute, storage, networking). SaaS provides applications, PaaS provides development platforms.

Indexes speed up data retrieval by creating optimized lookup structures, reducing the number of disk accesses needed to find data.

Encryption converts data into unreadable format, protecting it from unauthorized access during transmission and storage.

Merge Sort and Quick Sort have O(n log n) average complexity. Merge Sort guarantees this; Quick Sort can degrade to O(n²) in worst case.

The query optimizer analyzes different execution strategies and selects the one with minimal resource consumption and execution time.

Training data is used to teach AI models to recognize patterns. Test data evaluates accuracy; validation data prevents overfitting.

A deadlock occurs when two or more transactions wait for resources held by each other, creating a circular wait condition that prevents progress.

Eventual consistency is a model in NoSQL and distributed systems where updates propagate asynchronously, achieving consistency over time rather than immediately.