CHSE Odisha Elective Information Technology cheat sheet

Von Neumann architecture: CPU (ALU + control unit + registers), memory, input, output; instructions and data share the same memory.

CPU cycle = Fetch → Decode → Execute → Store; clock speed in GHz sets cycles per second, not instructions per second directly.

Primary memory is volatile RAM (SRAM fast/cache, DRAM main memory) or non-volatile ROM/Flash; secondary storage is non-volatile (HDD, SSD, optical).

Storage units: 1 KB = 1024 B, 1 MB = 1024 KB, 1 GB = 1024 MB, 1 TB = 1024 GB (binary prefixes).

Ports: USB (serial, hot-swappable), HDMI (digital audio+video), VGA (analog video), RJ-45 (Ethernet), 3.5 mm (analog audio).

Input devices convert physical signals to digital data; output devices do the reverse; a touchscreen is both.

Cache hierarchy L1 → L2 → L3 → RAM: smaller and faster closer to the CPU; hit ratio determines effective access time.

Firmware (BIOS/UEFI) runs POST at power-on and locates a bootable device before handing control to the OS loader.

OS roles: process management, memory management, file system management, device management, and user interface.

Process states: New → Ready → Running → Waiting → Terminated; the scheduler moves processes between Ready and Running.

Preemptive scheduling allows the OS to interrupt a running process; non-preemptive waits until it yields or finishes.

Deadlock requires four simultaneous conditions: mutual exclusion, hold-and-wait, no preemption, circular wait.

Absolute path starts at the root (C:\Users... or /home/...); relative path is resolved from the current working directory.

File extension maps to a default handler: .docx → word processor, .xlsx → spreadsheet, .html → browser, .exe → executable.

Virtual memory uses disk as an extension of RAM; thrashing is excessive page swapping that collapses throughput.

Common file operations: create, open, read, write, append, rename, copy, move, delete; delete removes the directory entry, not necessarily the data.

Styles (Heading 1, Heading 2, Normal) drive consistent formatting and enable automatic table of contents generation.

Character formatting affects selected text (font, size, bold, italic); paragraph formatting affects alignment, spacing, indents, and tabs.

Section breaks allow different page orientation, headers/footers, or column layouts within one document.

Mail merge requires a main document plus a data source (table/spreadsheet) with matching field names.

Track Changes records insertions and deletions with reviewer identity; Accept/Reject resolves each revision.

Find and Replace supports wildcards and special characters (^p paragraph mark, ^t tab) for pattern edits.

Tables of contents, captions, footnotes, and cross-references update automatically when fields are refreshed (F9).

Page setup controls margins, paper size, orientation, and gutter; header/footer distance is separate from body margins.

Cell reference types: A1 relative (adjusts on copy), $A$1 absolute (fixed), $A1 column-locked, A$1 row-locked.

Formula must begin with =; functions: SUM, AVERAGE, COUNT, COUNTA, COUNTIF, SUMIF, IF, VLOOKUP, INDEX, MATCH.

Error codes: #DIV/0! divide by zero, #REF! invalid reference, #NAME? unrecognized name, #VALUE! wrong type, #N/A lookup miss.

IF(logical_test, value_if_true, value_if_false) can nest; modern alternatives are IFS and SWITCH.

VLOOKUP(lookup_value, table_array, col_index, [range_lookup]) - FALSE/0 for exact match; lookup column must be the first column.

Charts: column for category comparison, line for trends over time, pie for parts of a whole (single series only), scatter for correlation.

Sorting and filtering (AutoFilter) rearrange or hide rows; pivot tables summarize by row/column/value fields without altering source data.

Relative vs absolute matters in fill operations; $ locks a coordinate so it does not shift when copied.

Slide master controls fonts, colors, and placeholder positions for all slides using that layout.

Transitions apply between slides; animations apply to objects within a slide; both can be timed or on-click.

Multimedia types: text, graphics (raster/vector), audio, video, animation; raster loses quality on scaling, vector does not.

Common image formats: JPEG (lossy, photos), PNG (lossless, transparency), GIF (256 colors, animation), SVG (vector).

Audio formats: MP3, WAV (uncompressed), AAC; video: MP4/H.264, AVI, MOV - codec and container are different concepts.

Resolution: 1920×1080 = Full HD, 3840×2160 = 4K; frame rate in fps affects perceived smoothness.

File size of uncompressed image ≈ width × height × color depth (bits) ÷ 8 bytes.

Export options: PPTX (editable), PDF (fixed layout), video (MP4), image-per-slide (PNG/JPEG).

Relational model: table (relation) = rows (tuples) + columns (attributes); primary key uniquely identifies a row; foreign key references another table's primary key.

Normalization: 1NF atomic values, 2NF no partial dependency on part of a composite key, 3NF no transitive dependency on a non-key attribute.

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

SELECT columns FROM table WHERE condition GROUP BY ... HAVING ... ORDER BY ...; WHERE filters rows before grouping, HAVING filters groups.

Joins: INNER (matching rows only), LEFT/RIGHT (all rows from one side), FULL (all rows), CROSS (Cartesian product).

Aggregate functions: COUNT, SUM, AVG, MIN, MAX; NULL is not equal to zero and is excluded by most aggregates.

ACID properties: Atomicity, Consistency, Isolation, Durability - transactional guarantees.

Entity–relationship model: entity, attribute, relationship, cardinality (1:1, 1:N, M:N); M:N requires a junction table.

OSI layers (top-down): Application, Presentation, Session, Transport, Network, Data Link, Physical; TCP/IP collapses to Application, Transport, Internet, Link.

TCP is connection-oriented and reliable (handshake, acknowledgments, retransmission); UDP is connectionless and best-effort.

IPv4 is 32-bit dotted decimal; IPv6 is 128-bit hexadecimal; private ranges 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.

DNS resolves domain names to IP addresses; DHCP assigns IP configuration automatically; NAT translates private to public addresses.

HTTP (port 80), HTTPS (443), FTP (20/21), SMTP (25), POP3 (110), IMAP (143), SSH (22), DNS (53).

Topologies: star (central switch), bus (shared backbone), ring, mesh (redundant paths); LAN vs WAN vs MAN by geographic scope.

Bandwidth is capacity (bps); latency is delay (ms); throughput is actual achieved rate; packet switching shares links.

URL anatomy: scheme://host:port/path?query#fragment; HTTP methods GET, POST, PUT, DELETE.

Document skeleton: , , (meta, title, link), (visible content).

Headings h1–h6;

paragraph;
line break;

Lists:

unordered,
ordered, description; items use
1. .

Tables:

Forms:

CSS can be inline (style attribute), internal (

HTML is structure, CSS is presentation, JavaScript is behavior - separation of concerns.

Character entities: < < , > > , & & , " " ,   non-breaking space.

Three control structures: sequence, selection (if/else, switch), iteration (for, while, do-while).

Variable is a named storage location; data types include integer, float, char, string, boolean; declaration vs initialization.

Operators: arithmetic (+ - * / %), relational (== != < > <= >=), logical (&& || !), assignment (=).

Algorithm properties: finiteness, definiteness, input, output, effectiveness; flowchart symbols: oval (start/end), parallelogram (I/O), rectangle (process), diamond (decision).

Loop types: for (known count), while (test before body), do-while (test after body - executes at least once).

Function/method: parameters in, return value out; local vs global scope; recursion needs a base case to terminate.

Array is an indexed collection of same-type elements; index usually starts at 0; length vs last index differ by one.

Compilation translates source to machine code before execution; interpretation translates and runs line by line; syntax errors vs logic errors.

Malware types: virus (attaches to files), worm (self-replicating over network), trojan (disguised), ransomware (encrypts for payment), spyware (collects data).

Phishing, smishing, and vishing are social-engineering attacks via email, SMS, and voice; verify sender and never share OTPs.

Strong password rules: length over complexity, unique per site, stored in a password manager, 2FA/MFA wherever offered.

Encryption protects confidentiality; hashing (SHA-256, MD5 weak) verifies integrity; digital signature provides authenticity and non-repudiation.

Firewall filters traffic by rules; antivirus uses signatures and heuristics; VPN encrypts traffic over an untrusted network.

IT Act 2000 (India) governs cyber offences and digital signatures; ethical use means authorized access only, respect privacy, and cite sources.

Emerging tech: cloud computing (IaaS/PaaS/SaaS), IoT, AI/ML, blockchain (distributed immutable ledger), 5G, edge computing.

Digital footprint is permanent; copyright vs plagiarism vs fair use; open-source licenses (GPL, MIT, Apache) differ in copyleft requirements.

Mixed references ($A1, A$1) lock one axis - useful for multiplication tables and rate tables.

COUNT counts numeric cells; COUNTA counts non-empty; COUNTBLANK counts empty; COUNTIF counts by condition.

SUMIF(range, criteria, sum_range) and SUMIFS(sum_range, criteria_range1, criteria1, ...) - criteria in quotes for text.

INDEX(array, row_num, column_num) returns a value; MATCH(lookup, range, 0) returns position; combined they replace VLOOKUP for left-lookups.

Conditional formatting highlights cells by rule without changing values; data validation restricts entry (list, whole number, date).

Freeze panes locks rows/columns on scroll; split view creates independent panes; print area and page setup control output.

Pivot table fields: Rows, Columns, Values, Filters; aggregation choices include Sum, Count, Average, Max, Min.

Goal Seek, Scenario Manager, and Solver are what-if tools; Data Table shows one or two variable sensitivity.

Search operators: "exact phrase", site:, filetype:, -exclude, OR; refine results with quotes and minus.

Web browser vs search engine: browser is client software (Chrome, Firefox); search engine is a service (Google, Bing).

Cookies store session state; first-party vs third-party cookies; cache stores static resources for faster reloads.

HTTPS uses TLS: server certificate, key exchange, symmetric session key; padlock indicates encrypted transport, not trustworthy content.

Email fields: To, Cc (visible copy), Bcc (hidden copy), Subject, Body, Attachment; SMTP sends, IMAP/POP3 retrieves.

Cloud storage vs local: sync, version history, sharing permissions (view/comment/edit); offline availability.

Bandwidth vs latency vs jitter; ping measures round-trip time; traceroute shows path hops.

Netiquette: no all-caps, quote context, respect privacy, avoid forwarding chain mail, verify before sharing.

Block elements start on a new line (div, p, h1); inline elements flow within text (span, a, strong, em).

Attributes: id (unique), class (reusable), style (inline CSS), title (tooltip), src/href (resource links).

Semantic tags improve accessibility and SEO: header, nav, main, article, section, aside, footer.

Box model: content → padding → border → margin; box-sizing: border-box includes padding and border in width.

Responsive design uses relative units (%, em, rem, vw/vh) and media queries @media (max-width: 600px) { ... }.

HTML5 input types: email, number, date, range, color, url, tel; required and pattern attributes enable client-side validation.

Image alt text describes content for screen readers; tables should not be used for page layout.

Validate markup with W3C validator; keep CSS in external files for caching and maintainability.

Truth tables: AND true only when both true; OR false only when both false; NOT inverts.

De Morgan's laws: NOT(A AND B) = (NOT A) OR (NOT B); NOT(A OR B) = (NOT A) AND (NOT B).

Swap two variables needs a temporary: temp = a; a = b; b = temp (or a = a + b; b = a - b; a = a - b).

Sum of first n integers = n(n+1)/2; factorial n! = n × (n-1)! with 0! = 1.

Linear search is O(n); binary search is O(log n) but requires a sorted array.

Bubble/selection/insertion sorts are O(n²); merge and quick sort average O(n log n).

Trace tables step through variables line by line to verify logic before coding.

Pseudocode uses indentation to show block structure; comments explain why, not what.

Confidentiality, Integrity, Availability (CIA triad) is the core security model.

Authentication verifies identity; authorization decides permissions; accounting/audit logs record actions.

Social engineering defenses: verify identity out-of-band, slow down under pressure, report suspicious requests.

Data privacy principles: minimal collection, purpose limitation, consent, retention limits, right to erasure.

AI ethics: bias in training data, transparency, accountability, human oversight for high-stakes decisions.

Blockchain properties: decentralization, immutability, consensus; smart contracts execute automatically.

Green computing: power management, e-waste recycling, virtualization to reduce hardware footprint.

Cyber law in India: IT Act 2000, amendments; SPDI rules; CERT-In advisories for incident reporting.

Scheduling algorithms: FCFS (simple, convoy effect), SJF (optimal average wait but needs burst prediction), Round Robin (time quantum), Priority.

Paging divides memory into fixed-size pages/frames; segmentation uses variable-size logical segments.

Context switch saves the state of one process and restores another; overhead has no useful work.

Semaphore and mutex protect critical sections; race condition occurs without synchronization.

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

Disk scheduling: FCFS, SSTF, SCAN, C-SCAN reduce seek time.

Command line basics: cd, dir/ls, mkdir, copy/cp, move/mv, del/rm, type/cat, cls/clear.

Backup types: full, incremental (changes since last backup), differential (changes since last full).

Motherboard hosts CPU socket, RAM slots, chipset, BIOS chip, expansion slots (PCIe), and I/O ports.

RAM types: DDR3/DDR4/DDR5 differ in speed and notch; capacity in GB, speed in MHz/MT/s.

SSD uses flash memory (no moving parts, fast); HDD uses spinning platters and read/write heads.

SMPS converts AC mains to DC voltages (3.3 V, 5 V, 12 V) for components.

GPU handles parallel graphics/matrix work; integrated graphics share system RAM.

Peripheral interfaces: USB 2.0 (480 Mbps), USB 3.x (5+ Gbps), Thunderbolt, SATA, NVMe.

POST beep codes indicate hardware faults; BIOS/UEFI settings configure boot order and virtualization.

Troubleshooting order: check power → connections → POST/beep → OS → drivers → hardware replacement.

Clipboard operations: cut (Ctrl+X), copy (Ctrl+C), paste (Ctrl+V), paste special (unformatted, values only).

Undo/redo (Ctrl+Z / Ctrl+Y); save vs save as (new name/location); autosave and version history.

Alignment: left, center, right, justify; line spacing single/1.5/double; paragraph spacing before/after.

Bullets vs numbering; multilevel lists; indentation with ruler markers; tab stops (left, center, right, decimal).

Insert: page break (Ctrl+Enter), section break, hyperlink, bookmark, comment, equation, symbol.

Review: spelling/grammar, thesaurus, word count, comments, compare documents, restrict editing.

Print options: print range (all, current page, selection), copies, collate, duplex.

Accessibility: alt text on images, heading structure, sufficient contrast, table header rows.

Slide layouts: title slide, title and content, two content, comparison, blank; placeholders inherit from master.

Speaker notes are invisible to audience but visible in presenter view.

Animation types: entrance, emphasis, exit, motion path; trigger on click, with previous, after previous.

Slide show modes: presenter view, browse by individual, kiosk (loops, auto-advance).

Consistent design: limit fonts (2), use contrast, align objects, avoid text walls, one idea per slide.

Embed vs link media: embed increases file size but is portable; link requires the source file.

Rehearse timings records slide durations for automatic playback.

Export to PDF preserves layout; export to video needs narration and timings configured.

CREATE TABLE defines columns, data types (INT, VARCHAR, DATE, DECIMAL), constraints (PRIMARY KEY, FOREIGN KEY, NOT NULL, UNIQUE, CHECK, DEFAULT).

INSERT INTO table (cols) VALUES (...); UPDATE table SET col=val WHERE cond; DELETE FROM table WHERE cond - omitting WHERE affects all rows.

ALTER TABLE adds/drops/modifies columns; DROP TABLE removes the table and its data.

SELECT DISTINCT removes duplicate rows; ORDER BY sorts ASC/DESC; LIMIT restricts rows.

Subquery returns a value or set used in WHERE/HAVING; EXISTS tests for row presence.

Views are stored queries that present a virtual table; indexes speed lookups but slow writes.

Referential integrity: foreign key value must exist in the referenced primary key or be NULL.

Backup/restore and access control (GRANT/REVOKE) protect data; transactions use COMMIT/ROLLBACK.

MAC address is 48-bit hardware address; IP address is logical and routable; ARP maps IP to MAC.

Subnet mask separates network and host bits; /24 = 255.255.255.0 = 254 usable hosts.

Router forwards between networks; switch forwards within a LAN by MAC; hub broadcasts to all ports.

Protocols: HTTP/HTTPS (web), SMTP/POP3/IMAP (mail), FTP/SFTP (files), DNS (names), DHCP (config), SSH (remote).

Wireless standards 802.11 a/b/g/n/ac/ax differ in band and speed; WPA2/WPA3 secure Wi-Fi.

Firewall rules allow/deny by port, IP, or protocol; DMZ hosts public-facing services.

Cloud service models: IaaS (infrastructure), PaaS (platform), SaaS (software); deployment: public, private, hybrid.

Network troubleshooting: ping (reachability), ipconfig/ifconfig (config), tracert (path), nslookup (DNS).

HTML5 doctype triggers standards mode; missing doctype causes quirks mode.

Meta viewport enables responsive scaling.

CSS selectors: element, .class, #id, descendant (space), child (>), attribute ([type="text"]), pseudo-class (:hover).

Flexbox: display:flex with justify-content (main axis) and align-items (cross axis).

Grid: display:grid with grid-template-columns and gap for two-dimensional layout.

Forms should include for accessibility; use method="post" for sensitive data.

SEO basics: title tag, meta description, heading hierarchy, descriptive alt text, clean URLs.

Hosting: static files on web server; domain name via registrar; DNS A record points to server IP.

String operations: length, substring, concatenation, comparison, case conversion, trim.

Type conversion: implicit (automatic promotion) vs explicit (cast); integer division truncates.

Short-circuit evaluation: A && B stops if A is false; A || B stops if A is true.

Nested loops: outer controls rows, inner controls columns; total iterations = outer × inner.

Break exits the loop; continue skips to the next iteration.

Pass by value copies the argument; pass by reference passes the address.

Debugging: read error message, reproduce, isolate, inspect variables, fix, retest.

Documentation: comments, meaningful names, modular functions, consistent indentation.

Backup rule 3-2-1: three copies, two media types, one off-site.

Software updates patch known vulnerabilities; end-of-support software is unsafe.

Public Wi-Fi risks: eavesdropping, rogue hotspots; use HTTPS and VPN.

Screen lock, device encryption, and remote wipe protect lost devices.

Verify URLs: check domain spelling, HTTPS, and padlock; hover links before clicking.

Report incidents to CERT-In, bank, and platform; preserve evidence (screenshots, logs).

Parental controls and safe search limit exposure for minors.

Digital signature verifies sender identity and message integrity using public-key cryptography.

Number systems: binary (base 2), octal (8), decimal (10), hexadecimal (16); convert by grouping bits (4 bits = 1 hex digit).

ASCII is 7-bit (128 characters); Unicode supports multilingual text; UTF-8 is variable-length.

Logic gates: AND, OR, NOT, NAND, NOR, XOR; truth tables define output for every input combination.

Half adder sums two bits (sum, carry); full adder includes carry-in.

Flip-flop stores one bit; register is a group of flip-flops.

Machine cycle time = 1 / clock frequency; e.g., 2 GHz = 0.5 ns per cycle.

Booting: cold boot from power-off; warm boot restarts without power cycle.

Peripheral categories: input, output, storage, and communication devices.

GUI vs CLI: GUI uses windows/icons/pointer; CLI uses typed commands and is scriptable.

Multitasking vs multiprocessing vs multithreading: concurrency models differ in resources shared.

User accounts and permissions: administrator/root vs standard user; least privilege principle.

File attributes: read-only, hidden, system, archive; timestamps record created/modified/accessed.

Disk utilities: format, defragment (HDD), check disk, disk cleanup.

Task manager/process list shows CPU, memory, and can terminate unresponsive processes.

Device drivers translate OS requests to hardware-specific commands.

Updates and patches fix bugs and security flaws; rollback restores previous state.

IFERROR(value, fallback) traps errors; IFNA catches only #N/A.

CONCATENATE or & joins text; TEXTJOIN adds delimiters; LEFT/RIGHT/MID extract substrings.

ROUND, ROUNDUP, ROUNDDOWN, INT, MOD for numeric control.

TODAY() and NOW() return current date/time; DATEDIF computes differences.

VLOOKUP with approximate match (TRUE) requires sorted data; exact match (FALSE) is safer.

Pivot charts visualize pivot table summaries and refresh with source data.

Named ranges improve readability and can be used in formulas and validation.

Absolute references are essential when copying a formula down a column that references a fixed rate cell.

Color models: RGB (additive, screens), CMYK (subtractive, print), HSL/HSV.

Resolution: PPI for print, DPI for printer dots; higher resolution = larger file.

Compression: lossy (JPEG, MP3, MP4) discards data; lossless (PNG, FLAC) preserves quality.

Animation principles: frame rate, keyframes, tweening, easing.

Audio sampling: sample rate (Hz) and bit depth determine quality and size; file size ≈ rate × depth × channels × seconds ÷ 8.

Video containers (MP4, AVI, MKV) hold video, audio, and subtitle streams.

Accessibility: captions for video, transcripts for audio, alt text for images.

Copyright: use licensed or public-domain media; credit creators.

LIKE with % (any sequence) and _ (single character) for pattern matching.

IN (list) and BETWEEN low AND high simplify range conditions.

JOIN ... ON condition combines tables; USING (column) when names match.

GROUP BY groups rows; HAVING filters groups after aggregation; ORDER BY sorts final output.

UNION combines result sets (removes duplicates); UNION ALL keeps duplicates.

NULL handling: IS NULL / IS NOT NULL; COALESCE returns first non-null value.

Constraints enforce data integrity; CASCADE deletes/updates related rows.

Normalization reduces redundancy and update anomalies; denormalization may improve read performance.

Client-server model: browser requests, server responds with status codes (200 OK, 404 Not Found, 500 Server Error).

Static vs dynamic pages: static served as-is; dynamic generated by server-side code.

URL vs URI vs URN: URI is the general identifier; URL locates a resource; URN names it persistently.

HTTP is stateless; cookies and sessions maintain state.

Web hosting types: shared, VPS, dedicated, cloud; domain registration and DNS records (A, CNAME, MX, TXT).

Search techniques: keywords, quotes, site:, filetype:, minus, OR; evaluate source credibility (author, date, domain).

Net neutrality and digital divide are social issues around internet access.

E-commerce models: B2B, B2C, C2C, B2G; payment security uses encryption and OTP.

HTML comments: ; comments are not displayed.

Nested elements must close in reverse order of opening.

and convey importance; and are stylistic only.

links to an element with matching id; opens email client.

is a void element (no closing tag); src and alt are essential attributes.

HTML5 semantic elements improve structure and accessibility over generic

Variable naming: start with a letter or underscore, no spaces, case-sensitive in most languages.

Constants cannot change after assignment; use for fixed values like PI.

Arithmetic precedence: parentheses, exponent, multiply/divide/mod, add/subtract.

Relational operators return boolean; assignment (=) differs from equality (==).

If-else chain vs switch: switch is cleaner for many discrete cases.

Loop counters must be initialized, tested, and updated to avoid infinite loops.

Flowchart vs pseudocode: flowchart is visual; pseudocode is text-like and language-agnostic.

Testing: normal, boundary, and invalid inputs reveal logic errors.