Developer Roadmaps & Core CS Academics

Model Answer: 1. Read Uncommitted (Suffers from Dirty Reads, Non-repeatable reads, Phantom reads). 2. Read Committed (Prevents Dirty Reads). 3. Repeatable Read (Prevents Dirty Reads & Non-repeatable reads, default in MySQL InnoDB). 4. Serializable (Prevents all phenomena, highest isolation, uses strict locking/MVCC).

Model Answer: In 3NF, for X -> A, A can be a prime attribute even if X is not a super key. In BCNF, X must ALWAYS be a super key. A relation with overlapping candidate keys (e.g. Student, Course, Instructor where Student+Course -> Instructor and Instructor -> Course) can be in 3NF but violates BCNF.

Model Answer: BSTs can degrade to O(N) without balancing and have high tree depth causing excessive disk I/O. Hash Tables provide O(1) point lookups but CANNOT perform range queries (`BETWEEN`, `>`, `<`). B+ Trees have a high branching factor (fanout), low disk I/O (depth 3-4 holds millions of rows), and linked leaf nodes for rapid range scans.

Model Answer: A Race Condition occurs when multiple threads concurrently read and write shared data, producing non-deterministic outcomes. A Mutex is a locking mechanism with ownership (only the thread that locked can unlock). A Semaphore is a signaling mechanism (integer counter) with wait() and signal() operations allowing N concurrent accesses.

Model Answer: Banker's algorithm tests for safety by simulating the allocation of predetermined maximum possible amounts of all resources, and then runs an algorithm to verify if there exists a 'Safe State' where all processes can complete without deadlock before actually granting the request.

Model Answer: Thrashing occurs when the system spends more time servicing page faults and swapping pages in and out of disk than executing actual instructions, causing CPU utilization to plummet. Resolved by increasing RAM, reducing the degree of multiprogramming, or using the Working Set Model.

Model Answer: 1. Browser checks local DNS cache -> OS cache -> Resolver query -> Root, TLD, Authoritative DNS to get IP. 2. ARP request resolves IP to Gateway MAC address. 3. TCP 3-way handshake (SYN, SYN-ACK, ACK). 4. TLS 1.3 cryptographic handshake (key exchange and certificate verification). 5. Browser sends HTTP GET request. 6. Server returns HTML response. 7. Browser parses DOM, fetches assets, and renders page.

Model Answer: A 2-way handshake cannot prevent duplicate or delayed old SYN packets from accidentally establishing a half-open ghost connection on the server. The 3-way handshake ensures that both client and server mutually verify each other's initial sequence numbers (ISNs) and confirm bidirectional communication capability.

Model Answer: The Diamond Problem occurs when class D inherits from classes B and C, which both inherit from class A, creating ambiguity over which superclass method D should execute. C++ resolves it using Virtual Inheritance (`virtual public A`). Java disallows multiple class inheritance altogether, allowing multiple inheritance only via Interfaces with default methods.

Model Answer: The classic Rectangle-Square problem: If `Square` inherits from `Rectangle` and overrides `setWidth(w)` to also change height to maintain squareness, a function expecting a generic `Rectangle` that sets width to 5 and height to 10 will fail unexpectedly. Square violates the mathematical invariants of Rectangle.