Karnataka KSEAB II PUC Information Technology (Vocational) cheat sheet

Von Neumann architecture: CPU (ALU + control unit + registers), memory, input, output, and storage units connected by a shared bus; instructions and data share the same memory.

Storage hierarchy by speed and cost: CPU registers > cache (L1/L2/L3) > RAM > SSD > HDD > optical/tape. Volatile memory loses contents on power loss; RAM and cache are volatile, ROM and flash are non-volatile.

Units: 1 byte = 8 bits; 1 KB = 1024 bytes; 1 MB = 1024 KB; 1 GB = 1024 MB; 1 TB = 1024 GB. A 4 GB RAM holds 4 × 1024 × 1024 × 1024 bytes.

Primary memory: RAM (SRAM = flip-flop based, faster, used in cache; DRAM = capacitor based, needs refresh, used as main memory) and ROM (PROM, EPROM, EEPROM, flash).

Ports and connectors: USB (serial, hot-swappable, supplies power), HDMI (digital audio + video), VGA (analog video), RJ-45 (Ethernet LAN), 3.5 mm audio jack, and PS/2 for legacy keyboards/mice.

Input devices convert human data to machine form (keyboard, mouse, scanner, MICR, OCR, OMR, barcode reader, biometric sensor); output devices convert machine data to human form (monitor, printer, plotter, speaker).

Printer decision rule: dot matrix = impact, multi-part carbon copies; inkjet = cheap colour, low volume; laser = high speed, low cost per page; plotter = large engineering drawings.

Clock speed (GHz) sets cycles per second; word length is the number of bits the CPU processes at once; a 64-bit CPU addresses far more RAM than a 32-bit CPU (about 4 GB limit).

BIOS/UEFI firmware runs POST at power-on, detects hardware, then loads the bootloader from the boot device into RAM.

An OS manages processor, memory, files, devices, and users; it provides process scheduling, memory allocation, file systems, and a user interface (CLI or GUI).

Process states: new → ready → running → waiting (blocked) → terminated. Only one process per CPU core is in the running state at a time.

Scheduling rules: FCFS is simple but causes convoy effect; SJF gives minimum average waiting time but needs burst-time knowledge; Round Robin gives each process a fixed time quantum for fair response.

Memory: paging divides memory into fixed-size frames and logical memory into pages, eliminating external fragmentation; segmentation uses variable-size logical segments.

Virtual memory lets programs exceed physical RAM by swapping pages to disk; thrashing is excessive page-fault swapping that collapses throughput.

File path rules: absolute path starts at the root (C:\Users\Me\a.txt or /home/me/a.txt); relative path is resolved from the current working directory; .. means parent directory and . means current directory.

Common extensions: .txt plain text, .docx Word, .xlsx Excel, .pptx PowerPoint, .pdf portable fixed layout, .jpg/.png images, .mp3 audio, .mp4 video, .exe executable, .zip compressed archive.

GUI file operations: copy duplicates (Ctrl+C, Ctrl+V), cut moves (Ctrl+X, Ctrl+V), delete sends to Recycle Bin (Shift+Delete bypasses it), rename changes the name but not the contents.

Utility roles: antivirus, disk defragmenter (HDD only; SSDs should not be defragmented), disk cleanup, backup, compression, and device drivers.

Word processor objects: character, paragraph, section, page. Paragraph formatting (alignment, indents, line spacing, tabs) applies to whole paragraphs; character formatting (font, size, bold, italic, colour) applies to selected text.

Alignment shortcuts: Ctrl+L left, Ctrl+E centre, Ctrl+R right, Ctrl+J justify. Justified text stretches spaces so both margins are flush.

Line spacing options: single, 1.5, double, exactly, and multiple. Paragraph spacing sets space before and after a paragraph, distinct from line spacing.

Styles apply named formatting sets; the Heading 1/2/3 styles feed the automatic table of contents (References → Table of Contents) and the navigation pane.

Mail merge order: create main document → select or create the data source → insert merge fields → preview results → finish and merge. It produces one personalised copy per data record.

Headers and footers repeat on every page of a section; page numbering can restart per section, and different first-page or odd/even headers are options.

Track Changes records insertions and deletions for review; Comments attach notes without altering text; Accept/Reject resolves each change.

Find and Replace supports wildcards and formatting-based replacement; Ctrl+H opens Replace, Ctrl+F opens Find, Ctrl+Z undoes and Ctrl+Y redoes.

Print settings: orientation (portrait/landscape), paper size (A4 = 210 × 297 mm), margins, scaling (fit to 1 page), and print range (all pages, current page, selection).

Cell reference types: relative (A1) shifts when copied; absolute ($A$1) stays fixed; mixed ($A1 fixes column, A$1 fixes row). Pressing F4 cycles the $ placement.

Operator precedence: : and space (range operators) > negation – > % > ^ > * and / > + and – > & (concatenation) > comparison (=, <, >, <=, >=, <>).

Formula vs function: every formula begins with = ; a function is a named formula such as =SUM(A1:A10) or =AVERAGE(B2:B9).

Error values: #DIV/0! divide by zero; #VALUE! wrong data type; #REF! deleted/invalid reference; #NAME? unrecognised name; #N/A value not available; #### column too narrow.

Logical functions: =IF(condition, value_if_true, value_if_false); =AND(...) is TRUE only if all arguments are TRUE; =OR(...) is TRUE if any argument is TRUE; =COUNTIF(range, criteria) counts matches.

Lookup rule: =VLOOKUP(lookup_value, table_array, col_index, FALSE) searches the first column for an exact match and returns a value from the stated column; TRUE or 1 allows approximate match on sorted data.

Aggregation: =COUNT counts numbers, =COUNTA counts non-empty cells, =COUNTBLANK counts empty cells; =SUMIF(range, criteria, sum_range) adds only matching rows.

Chart choice: column/bar for comparison, line for trend over time, pie for parts of one whole (few categories), scatter for correlation between two numeric variables.

Sorting rearranges rows by a key (ascending/descending, multi-level); filtering hides non-matching rows without deleting them; both must be applied to the whole data range to keep records intact.

Slide structure: title slide, content slides, section dividers, closing slide. The slide master controls fonts, colours, and placeholder positions for all slides using that layout.

Views: Normal (edit one slide), Slide Sorter (reorder many), Notes Page (speaker notes), Reading/Slide Show (delivery), Outline (text-only structure).

Transitions apply between slides (one per slide); animations apply to objects inside a slide (entrance, emphasis, exit, motion path).

Animation triggers: On Click, With Previous, After Previous. Setting After Previous with a delay creates automatic sequencing without presenter input.

Multimedia elements: raster images (JPEG, PNG, GIF, BMP - pixel-based, lose quality on scaling) vs vector graphics (SVG, WMF - resolution-independent).

Audio/video formats: MP3 and WAV audio; MP4 (H.264) and AVI video. Embedding stores the file inside the presentation; linking keeps a path reference and breaks if the file moves.

File size reduction rules: compress pictures to lower resolution, remove trimmed media, use solid colour backgrounds instead of large images, and embed only the fonts actually used.

Delivery aids: speaker notes are visible only to the presenter in Presenter View; rehearse timings records slide durations for a self-running show; a custom slide show plays a chosen subset.

Accessibility: alt text on images, minimum readable font size (about 24 pt for body text), high contrast, and captions for audio/video content.

DBMS vs file system: a DBMS reduces redundancy, enforces integrity and concurrent access, provides backup/recovery, and separates data from programs through a schema.

Relational model terms: relation = table, tuple = row/record, attribute = column/field, degree = number of attributes, cardinality = number of tuples, domain = allowed values of an attribute.

Keys: super key uniquely identifies tuples; candidate key is a minimal super key; primary key is the chosen candidate key (unique and NOT NULL); foreign key references another table's primary key and enforces referential integrity.

SQL DDL: CREATE TABLE, ALTER TABLE, DROP TABLE. SQL DML: SELECT, INSERT, UPDATE, DELETE. DDL changes structure; DML changes data.

SELECT clause order: SELECT … FROM … WHERE … GROUP BY … HAVING … ORDER BY. WHERE filters rows before grouping; HAVING filters groups after aggregation.

Aggregate functions: COUNT, SUM, AVG, MIN, MAX. They ignore NULL except COUNT(*), which counts all rows.

Joins: INNER JOIN returns matching rows only; LEFT JOIN returns all left-table rows plus matches; a Cartesian product (no join condition) returns rows = rows(A) × rows(B).

Normalisation: 1NF removes repeating groups (atomic values); 2NF removes partial dependency on part of a composite key; 3NF removes transitive dependency of non-key attributes on other non-key attributes.

ACID properties: Atomicity (all or nothing), Consistency (valid state to valid state), Isolation (concurrent transactions do not interfere), Durability (committed data survives failure).

Program development cycle: problem definition → algorithm/flowchart → coding → compilation/interpretation → testing and debugging → documentation and maintenance.

Flowchart symbols: oval = start/stop, parallelogram = input/output, rectangle = process, diamond = decision, arrow = flow direction, circle = connector.

Data types: integer (whole numbers), float/real (decimals), char (one character), string (text), boolean (true/false). Type mismatch causes errors or implicit conversion.

Control structures: sequence, selection (if, if-else, switch/case), iteration (while = pre-test, do-while = post-test runs at least once, for = counted loop).

Operators: arithmetic (+ – * / % ), relational (< > <= >= == !=), logical (AND, OR, NOT). AND is true only if both operands are true; NOT negates.

Variable vs constant: a variable's value can change during execution; a constant is assigned once and cannot be reassigned. A variable must be declared before use in strongly typed languages.

Array: a collection of same-type elements stored in contiguous memory and accessed by index, usually starting at 0. Traversal requires a loop bounded by the array length.

Function vs procedure: a function returns a value; a procedure performs an action without returning one. Parameters pass by value (copy) or by reference (address).

Search and sort: linear search scans each element (O(n)); binary search requires sorted data and halves the range (O(log n)); bubble sort repeatedly swaps adjacent out-of-order pairs.

HTML defines structure, CSS defines presentation, JavaScript defines behaviour. HTML elements use opening and closing tags; empty elements such as
, , and

Document skeleton: , , (title, meta, link to CSS), (visible content). The appears in the browser tab, not in the page body.</p>

Common tags:

paragraph, hyperlink, image,

/
/
1. lists, //

   tables, with , ,

CSS rule anatomy: selector { property: value; }. Selectors: element (p), class (.note), id (#main). Inline style beats internal

URL anatomy: protocol://host:port/path?query#fragment, e.g. https://example.com:443/page?id=5#top. Default ports: HTTP 80, HTTPS 443, FTP 21, SMTP 25.

HTTP methods: GET retrieves data and appends parameters to the URL; POST sends data in the request body. Status codes: 200 OK, 301 moved, 404 not found, 500 server error.

Domain names are read right to left by hierarchy: host, second-level, top-level domain (.com, .org, .in, .edu). DNS resolves names to IP addresses.

Static vs dynamic pages: static pages return the same stored file; dynamic pages are generated per request by server-side code querying a database.

Client–server model: the browser (client) sends a request; the web server responds with status, headers, and body. Cookies store small client-side state between requests.

Network types by span: PAN (a few metres), LAN (building/campus), MAN (city), WAN (countries). The Internet is the largest WAN.

Topologies: star (central switch/hub; one cable failure isolates one node), bus (shared backbone; a backbone break downs the segment), ring (token passing), mesh (every node linked; maximum redundancy, highest cabling cost).

Transmission media: twisted pair (RJ-45, up to 100 m), coaxial cable, fibre optic (light pulses, high bandwidth, immune to EMI), and wireless (radio, microwave, satellite).

Bandwidth is capacity in bits per second; latency is delay in milliseconds; throughput is actual achieved rate. Bandwidth and latency are independent measures.

Switching: circuit switching reserves a dedicated path (telephone); packet switching splits data into packets routed independently (Internet).

OSI seven layers, bottom to top: Physical, Data Link, Network, Transport, Session, Presentation, Application. TCP/IP maps to four layers: Network Access, Internet, Transport, Application.

Protocols: IP (addressing/routing), TCP (reliable, ordered, connection-oriented), UDP (unreliable, fast, connectionless), HTTP/HTTPS (web), FTP (file transfer), SMTP (send mail), POP3/IMAP (receive mail), DNS (name resolution), DHCP (automatic IP assignment).

IPv4 is 32-bit dotted decimal (e.g. 192.168.1.10); IPv6 is 128-bit hexadecimal. Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16. Loopback is 127.0.0.1.

Devices: hub broadcasts to all ports (Layer 1), switch forwards by MAC address (Layer 2), router forwards by IP address between networks (Layer 3), modem converts between digital and analog/signal carrier.

Malware classes: virus (attaches to files, needs a host), worm (self-replicating across networks), trojan (disguised as legitimate software), ransomware (encrypts data for payment), spyware (secretly collects data), adware.

Phishing, vishing, and smishing are social-engineering attacks delivering fake messages by email, voice call, and SMS to steal credentials. Spear phishing targets a specific person.

Password rules: long unique passphrases, never reused across sites, combined with multi-factor authentication. A hash stores a one-way digest; encryption is reversible with a key.

Encryption: symmetric uses one shared key (fast, key-distribution problem); asymmetric uses a public/private key pair (key exchange, digital signatures). HTTPS combines both.

Firewall filters traffic by rules; antivirus matches signatures and heuristics; VPN creates an encrypted tunnel; IDS detects and alerts; IPS detects and blocks.

Cyber-ethics: do not access systems without authorisation, respect copyright and software licences, protect personal data, and report vulnerabilities responsibly rather than exploiting them.

Indian legal framework: Information Technology Act, 2000 (amended 2008) covers cybercrime and electronic signatures; the DPDP Act, 2023 governs processing of digital personal data.

Cloud service models: IaaS (virtual machines, storage), PaaS (runtime and development platform), SaaS (ready applications). Deployment: public, private, hybrid.

Emerging technologies: AI/ML (learning from data), IoT (networked sensors), blockchain (distributed immutable ledger), big data (volume, velocity, variety), edge computing (processing near the source), 5G (high bandwidth, low latency).