RSSB Computer Instructor cheat sheet

Von Neumann architecture: CPU (ALU + control unit + registers) fetches instructions and data from the same memory via the stored-program concept; the fetch-decode-execute cycle repeats per instruction.

Memory hierarchy by speed and cost per bit: registers > cache (L1/L2/L3) > main memory (RAM) > secondary storage (SSD/HDD) > tertiary (tape); capacity and access latency increase downward.

Number systems: binary base 2, octal base 8, decimal base 10, hexadecimal base 16; hex digit maps to exactly 4 bits, octal digit to 3 bits. 1 KB = 2^10 bytes, 1 MB = 2^20, 1 GB = 2^30.

Two's complement: to negate a binary number, invert all bits and add 1; an n-bit signed range is -2^(n-1) to +2^(n-1)-1.

Logic gates: AND outputs 1 only if all inputs 1; OR outputs 1 if any input 1; XOR outputs 1 for odd parity of inputs; NAND and NOR are universal gates.

Combinational circuits (adders, multiplexers, decoders) have no memory; sequential circuits (flip-flops, registers, counters) hold state and are clock-driven.

RISC favors a small fixed-length instruction set, many registers and pipelining; CISC favors complex variable-length instructions and microcode.

Bus types: address bus width sets addressable memory (n lines → 2^n locations); data bus width sets word transfer size; control bus carries read/write and interrupt signals.

Process states: new → ready → running → waiting → terminated; only one process per core is running at a time, and a context switch saves/restores the PCB.

CPU scheduling: FCFS (convoy effect), SJF (optimal average waiting time but needs burst prediction), Round Robin (time quantum), priority (starvation risk, fixed by aging).

Deadlock's four Coffman conditions: mutual exclusion, hold and wait, no preemption, circular wait; all four must hold simultaneously.

Banker's algorithm is a deadlock-avoidance method that grants a request only if the system stays in a safe state.

Paging divides logical memory into fixed-size pages and physical memory into frames; the TLB caches page-table entries; a page fault traps to the OS.

Thrashing is excessive paging caused by too-small a frame allocation; the working-set model estimates the pages a process needs in a time window.

File allocation methods: contiguous (fast, external fragmentation), linked (no fragmentation, no random access), indexed (random access via index block).

Disk scheduling: SSTF minimizes seek but can starve; SCAN (elevator) and C-SCAN give bounded wait; FCFS is fair but slow.

OSI seven layers top-down: Application, Presentation, Session, Transport, Network, Data Link, Physical; TCP/IP collapses the top three into Application.

Encapsulation adds headers downward: transport (TCP/UDP) → network (IP) → data link (frame) → physical (bits); decapsulation reverses it at the receiver.

IPv4 address is 32 bits; IPv6 is 128 bits. Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.

Subnetting: usable hosts = 2^h - 2, where h is the number of host bits; /24 leaves 8 host bits, so 254 usable addresses.

TCP is connection-oriented, reliable, ordered, with flow control (sliding window) and congestion control; UDP is connectionless and best-effort.

Three-way handshake: SYN → SYN-ACK → ACK. Port numbers: well-known 0–1023, registered 1024–49151, dynamic/ephemeral 49152–65535.

Media access: CSMA/CD for Ethernet (collision detection), CSMA/CA for Wi-Fi (collision avoidance); switches forward by MAC, routers by IP.

DNS resolves names to IPs; DHCP assigns addresses dynamically; ARP maps IP to MAC on a LAN; NAT translates private to public addresses.

ACID properties: Atomicity (all-or-nothing), Consistency (constraints preserved), Isolation (concurrent transactions do not interfere), Durability (committed data survives failure).

Relational keys: superkey, candidate key, primary key (unique, not null), foreign key (references a candidate key, enforces referential integrity).

Normal forms: 1NF atomic attributes; 2NF no partial dependency on part of a composite key; 3NF no transitive dependency; BCNF every determinant is a candidate key.

SQL command groups: DDL (CREATE, ALTER, DROP), DML (INSERT, UPDATE, DELETE), DQL (SELECT), DCL (GRANT, REVOKE), TCL (COMMIT, ROLLBACK).

Joins: INNER returns matching rows; LEFT/RIGHT return all rows from one side with NULLs; FULL returns all; CROSS returns the Cartesian product.

Aggregate functions (COUNT, SUM, AVG, MIN, MAX) collapse rows; GROUP BY forms groups, HAVING filters groups, WHERE filters rows before grouping.

Indexes speed up SELECT and slow INSERT/UPDATE/DELETE; a B+ tree index keeps all data in leaves and supports range scans.

Concurrency control: two-phase locking (growing and shrinking phases); a schedule is conflict-serializable if its precedence graph is acyclic.

Complexity order: O(1) < O(log n) < O(n) < O(n log n) < O(n^2) < O(2^n) < O(n!); binary search is O(log n) on sorted arrays.

Array access is O(1); linked-list insertion/deletion at a known node is O(1), but search is O(n); a stack is LIFO, a queue is FIFO.

Sorting: bubble/insertion/selection O(n^2); merge sort O(n log n) always but O(n) extra space; quicksort average O(n log n), worst O(n^2); heap sort O(n log n) in place.

Binary search tree: inorder traversal yields sorted order; average search O(log n), worst O(n) when skewed; AVL/red-black trees rebalance to O(log n).

Hash table average lookup O(1); collisions resolved by chaining or open addressing (linear/quadratic probing, double hashing); load factor triggers resizing.

Graph representations: adjacency matrix O(V^2) space, adjacency list O(V+E); BFS uses a queue and finds shortest unweighted paths; DFS uses a stack/recursion.

Dijkstra's algorithm finds single-source shortest paths with non-negative weights in O((V+E) log V) with a binary heap; it fails on negative edges.

Recursion needs a base case and a recursive case; each call consumes stack space, so deep recursion risks stack overflow.

SDLC phases: requirements → design → implementation → testing → deployment → maintenance; Waterfall is sequential, Agile is iterative and incremental.

Testing levels: unit → integration → system → acceptance; black-box tests behavior, white-box tests internal paths and coverage.

COCOMO estimates effort as a function of size in KLOC and cost drivers; function points measure size from inputs, outputs, files, and queries.

HTML structures content; CSS styles it (selectors, box model: content, padding, border, margin); JavaScript adds behavior in the browser.

HTTP methods: GET (safe, idempotent), POST (creates), PUT (idempotent replace), DELETE; status codes 2xx success, 3xx redirect, 4xx client error, 5xx server error.

Client-server vs three-tier: presentation, application logic, and data tiers; REST uses stateless resources identified by URIs.

Version control with Git: commit snapshots, branch isolates work, merge combines histories, pull request reviews changes before integration.

Software quality attributes: reliability, maintainability, usability, portability, efficiency; cohesion should be high and coupling low.

CIA triad: confidentiality (encryption, access control), integrity (hashing, checksums), availability (redundancy, DDoS protection).

Symmetric encryption uses one shared key (AES, DES); asymmetric uses a public/private pair (RSA, ECC); hashing (SHA-256) is one-way and detects tampering.

Digital signature: sign with the sender's private key, verify with the sender's public key; it provides authentication, integrity, and non-repudiation.

Malware classes: virus (needs a host), worm (self-replicating over networks), trojan (disguised), ransomware (encrypts and demands payment), spyware (collects data).

Attack types: phishing (deceptive messages), SQL injection (unsanitized input), XSS (injected scripts), man-in-the-middle, brute force, denial of service.

Firewall filters packets by rules; IDS detects and alerts, IPS detects and blocks; VPN creates an encrypted tunnel over an untrusted network.

India's IT Act 2000 (amended 2008) governs electronic records and digital signatures; Sections 65, 66, 66C, 66D, and 67 cover tampering, computer fraud, identity theft, cheating by personation, and obscene content.

The Digital Personal Data Protection Act 2023 regulates processing of digital personal data in India, with consent and purpose-limitation obligations on data fiduciaries.

Boolean identities: A + A' = 1, A·A' = 0, A + AB = A, A + A'B = A + B (absorption); De Morgan: (A·B)' = A' + B', (A+B)' = A'·B'.

Karnaugh map groups of 1, 2, 4, 8 adjacent cells eliminate 0, 1, 2, 3 variables respectively; grouping wraps around edges.

Half adder: Sum = A ⊕ B, Carry = A·B; full adder adds a carry-in and can be chained for multi-bit addition.

Flip-flops: SR (set-reset, invalid state when both 1), JK (toggles when both 1), D (data latch), T (toggle); edge-triggered devices sample on a clock edge.

Registers store a word; shift registers move bits serially; counters divide frequency and count clock pulses modulo their modulus.

Instruction pipeline stages: fetch, decode, execute, memory, write-back; hazards are structural, data (fixed by forwarding/stalling), and control (fixed by branch prediction).

Cache mapping: direct (one line per set), fully associative (any line), set-associative (n-way); write-through updates memory immediately, write-back defers until eviction.

Amdahl's law: speedup = 1 / ((1 - p) + p/s), where p is the parallel fraction and s the improvement factor.

Rajasthan is India's largest state by area (about 342,239 km²); Jaipur is the capital; the state was formed in stages, with the final unification completed in 1956.

Physiographic divisions: Thar Desert (west), Aravalli Range (central, including Guru Shikhar at about 1,722 m, the highest peak), eastern plains, and the Hadoti plateau.

Major rivers: Chambal (perennial, forms the boundary with Madhya Pradesh), Banas (entirely within Rajasthan), Luni (saline, drains into the Rann of Kutch), Mahi, and Sabarmati.

Forts of Rajasthan: Chittorgarh, Kumbhalgarh, Ranthambore, Amber, Jaisalmer, and Gagron are UNESCO World Heritage hill forts; Keoladeo National Park and Ranthambore are notable protected areas.

Fairs and festivals: Pushkar Camel Fair (Kartik), Teej (Jaipur), Gangaur (spring), Desert Festival (Jaisalmer), and the Baneshwar fair (Dungarpur).

Dance forms: Ghoomar (Bhil/aristocratic), Kalbelia (Kalbelia community, UNESCO intangible heritage), Gair (Mewar), and Chari.

Administrative facts: the state has 7 divisional headquarters and 33 districts; the Rajasthan High Court is at Jodhpur, and the Rajasthan Public Service Commission is at Ajmer.

Current affairs items (verify the latest figures before the exam): Rajasthan's education and IT initiatives, new districts and divisions announced by the state government, and central schemes active in the state.

Hindi संधि: स्वर संधि (दो स्वरों का मेल, जैसे विद्या + आलय = विद्यालय), व्यंजन संधि, विसर्ग संधि; संधि-विच्छेद करके प्रकार पहचानें।

समास के भेद: तत्पुरुष (अंतिम पद प्रधान), कर्मधारय (विशेषण-विशेष्य), द्विगु (संख्यावाचक), द्वंद्व (दोनों पद प्रधान), बहुव्रीहि (अन्य पद प्रधान)।

उपसर्ग अर्थ बदलते हैं (अ, अन, नि, प्र, वि, सु) और प्रत्यय शब्द के अंत में जुड़ते हैं (ता, त्व, आई, इक); इनसे बने शब्दों की पहचान करें।

मुहावरे और लोकोक्तियाँ: मुहावरा वाक्यांश है जिसका अर्थ शब्दों के सीधे अर्थ से भिन्न होता है; लोकोक्ति पूर्ण वाक्य रूप में कहावत है।

कारक और विभक्ति चिह्न: कर्ता ने, कर्म को, करण से/के द्वारा, संप्रदान के लिए, अपादान से (अलग होना), अधिकरण में/पर।

English parts of speech: noun, pronoun, verb, adjective, adverb, preposition, conjunction, interjection; a clause has a subject and a predicate, a phrase does not.

Tense consistency: simple present for habits, present continuous for ongoing actions, present perfect for past actions with present relevance, past perfect for the earlier of two past events.

Active to passive: object becomes subject, verb becomes be + past participle, subject moves to a by-phrase; only transitive verbs can be made passive.

Bloom's taxonomy (revised): Remember, Understand, Apply, Analyze, Evaluate, Create; lower-order objectives precede higher-order ones in lesson design.

Teaching methods: lecture (efficient for large groups), demonstration (shows procedure), project (learner-driven), problem-solving (inquiry), and discussion (peer interaction).

Assessment types: formative (during learning, feedback-oriented), summative (end of unit, judgment), diagnostic (before teaching, identifies gaps), and placement (determines level).

Learning theories: behaviorism (stimulus-response, reinforcement), cognitivism (information processing), constructivism (learners build knowledge from experience), and connectivism (networked learning).

A teaching aid is effective when it is relevant to the objective, simple, visible to all learners, and integrated into the lesson rather than used as decoration.

Individual differences: learners vary in prior knowledge, pace, learning style, and motivation; differentiated instruction adjusts content, process, or product.

Classroom management: establish clear rules and routines, use proximity and non-verbal cues, and reinforce positive behavior rather than only punishing misbehavior.

Inclusive education: adapt materials and assessment for learners with disabilities, use multiple representations, and ensure physical and curricular access.