Maharashtra HSC IT (Arts) cheat sheet

Data flows Input → Process (CPU) → Output, with storage holding data permanently; CPU = ALU (arithmetic/logic) + Control Unit + registers.

Memory hierarchy by speed and cost: registers > cache > RAM > SSD/HDD > optical/tape; RAM is volatile, ROM is non-volatile and holds firmware/BIOS.

Units: 1 byte = 8 bits; 1 KB = 1024 B, 1 MB = 1024 KB, 1 GB = 1024 MB, 1 TB = 1024 GB.

Input devices convert human data to machine form (keyboard, mouse, scanner, mic, barcode reader); output devices do the reverse (monitor, printer, speaker, plotter).

Ports: USB is hot-swappable and supplies power; HDMI carries digital audio+video; VGA is analog video only; Ethernet (RJ-45) is for LAN.

Printers: impact (dot matrix, uses ribbon, multi-part carbon copies) vs non-impact (inkjet, laser uses toner and a drum); DPI measures print resolution.

Clock speed in GHz sets cycles per second; more cores allow parallel execution but do not multiply single-thread speed.

Cache memory sits between CPU and RAM; larger cache reduces average memory access time; SRAM is used for cache, DRAM for main memory.

OS roles: process management, memory management, file management, device management (via drivers), and user interface (CLI or GUI).

Single-user vs multi-user and single-tasking vs multitasking describe concurrency; time-sharing gives each process a time slice.

File name = name + extension; extension maps to file type (.docx document, .xlsx spreadsheet, .pptx presentation, .txt plain text, .jpg image, .mp3 audio, .mp4 video, .exe executable).

Path types: absolute starts from the root (C:\Users\Me\file.txt); relative starts from the current working directory.

Wildcards: * matches any number of characters, ? matches exactly one character (e.g., report?.docx).

File operations: create, open, save, save as (new name/format), rename, copy, move, delete; delete usually sends to Recycle Bin, Shift+Delete bypasses it.

Folder tree: root → parent → child; a folder can hold files and subfolders; the same file name cannot exist twice in one folder.

Attributes such as read-only, hidden, and system restrict or conceal a file; read-only blocks editing but not opening.

Character formatting changes individual characters (font, size in points, bold/italic/underline, colour); paragraph formatting changes alignment, indents, spacing, and line spacing.

Alignment options: left, centre, right, justify; justify stretches spaces so both margins are flush.

Line spacing (single, 1.5, double) is space between lines of one paragraph; paragraph spacing is space before/after the paragraph.

Header appears at the top of every page, footer at the bottom; page numbers are inserted as fields so they renumber automatically.

Find locates text, Replace substitutes it; Replace All changes every occurrence at once.

Tables are organised in rows and columns of cells; cells can merge or split; a table can be sorted or converted to text.

Mail Merge combines a main document with a data source (list of names/addresses) to produce many personalised copies.

Track Changes records insertions/deletions for review; Comments attach notes without altering the text; Accept/Reject resolves them.

Spell check flags possible errors against a dictionary; grammar check reviews sentence structure; neither replaces human proofreading.

Cell reference = column letter + row number (B5); a range is written with a colon (A1:C10).

Relative reference (A1) shifts when copied; absolute reference ($A$1) stays fixed; mixed ($A1 or A$1) locks only row or only column.

Every formula starts with = ; arithmetic operators are + - * / ^ with ^ for exponent; % is percent.

Common functions: =SUM(range), =AVERAGE(range), =MAX(range), =MIN(range), =COUNT(range) counts numbers, =COUNTA(range) counts non-empty cells, =ROUND(number, digits).

Conditional logic: =IF(condition, value_if_true, value_if_false); comparisons use =, <>, >, <, >=, <=.

=COUNTIF(range, criterion) counts matching cells; =SUMIF(range, criterion, sum_range) adds matching values.

Sorting rearranges rows by a key column; filtering hides non-matching rows without deleting them.

A chart type follows data purpose: column for comparison, line for trend over time, pie for parts of one whole, scatter for correlation.

Error values: #DIV/0! division by zero, #REF! deleted reference, #NAME? unrecognised name, #VALUE! wrong data type.

A presentation is a series of slides; a slide layout defines placeholders for title, text, and objects; a theme sets fonts, colours, and effects consistently.

Slide Master controls formatting for all slides at once; changes made there propagate to every slide using that layout.

Slide Show views: Normal for editing, Slide Sorter for reordering, Slide Show (F5) for full-screen delivery; B blanks the screen during a show.

Transitions are effects between slides; animations are effects applied to objects within a slide; too many of either distract the audience.

Multimedia = text + graphics + audio + video + animation; bitmapped images lose quality when enlarged, vector images scale without loss.

Image formats: JPEG for photos (lossy), PNG for graphics with transparency (lossless), GIF for simple animation and 256 colours.

Audio: MP3 and WAV are common; WAV is uncompressed and larger, MP3 is compressed and smaller. Video: MP4 is widely used for compressed video.

Resolution and aspect ratio: 1920×1080 is 16:9 (widescreen); 1024×768 is 4:3; higher resolution gives sharper projection but larger files.

Internet is the global network of networks; the World Wide Web is a service on it accessed by HTTP/HTTPS.

URL structure: protocol://domain/path (e.g., https://www.example.com/page.html); HTTPS encrypts traffic with TLS, HTTP does not.

A browser renders web pages; a search engine indexes pages and returns results; a web page is written in HTML and styled with CSS.

Email address form: local-part@domain (e.g., [email protected]); the @ separates mailbox from mail server domain.

Email fields: To (primary recipients), Cc (carbon copy, visible to all), Bcc (blind copy, hidden from other recipients), Subject, Body, Attachment.

Reply goes to sender only; Reply All goes to sender plus all recipients in To and Cc; Forward sends the message to a new recipient.

Netiquette: no ALL CAPS (reads as shouting), keep subject lines meaningful, quote only relevant text, scan attachments before opening.

Cookies are small files a site stores in the browser to remember state; clearing them logs you out and resets preferences.

Network sizes: PAN (personal, ~10 m Bluetooth), LAN (building/campus), MAN (city), WAN (countries; the Internet is the largest WAN).

Topologies: star (central switch, single point of failure at hub), bus (shared backbone, collision-prone), ring (token order), mesh (redundant, costly).

Transmission media: twisted pair (Ethernet, limited distance), coaxial, fibre optic (high bandwidth, immune to EMI), and wireless (radio, microwave).

Bandwidth is capacity (bits per second); latency is delay; throughput is actual achieved rate; 1 Mbps = 10^6 bits/s.

IP address identifies a device on a network; IPv4 is 32-bit dotted decimal (e.g., 192.168.1.1), IPv6 is 128-bit hexadecimal.

DNS translates domain names to IP addresses; DHCP assigns IP addresses automatically; a router forwards traffic between networks.

Protocols: HTTP/HTTPS for web, SMTP for sending mail, POP3/IMAP for receiving, FTP for file transfer, TCP (reliable) and UDP (fast, unreliable).

Client-server: a server provides a service to clients; peer-to-peer: each node acts as both client and server.

A database is an organised collection of related data; a DBMS is software to create, store, and query it (e.g., MySQL, Oracle).

A table (relation) holds data in rows (records/tuples) and columns (fields/attributes); each column has one data type.

Primary key uniquely identifies each row and cannot be NULL; foreign key in one table references the primary key of another and enforces referential integrity.

SQL categories: DDL (CREATE, ALTER, DROP), DML (INSERT, UPDATE, DELETE), DQL (SELECT).

SELECT syntax: SELECT columns FROM table WHERE condition ORDER BY column ASC|DESC;

WHERE operators: =, <>, >, <, >=, <=, BETWEEN a AND b, IN (list), LIKE with % (any characters) and _ (one character).

Aggregate functions: COUNT(*), SUM(col), AVG(col), MAX(col), MIN(col); GROUP BY groups rows and HAVING filters groups (WHERE filters rows).

DISTINCT removes duplicate rows from output; NULL is unknown and is tested with IS NULL / IS NOT NULL, never with = NULL.

Phishing is a fake message that lures credentials; indicators are urgent threats, mismatched sender domain, and unexpected links or attachments.

Malware types: virus (attaches to files), worm (self-replicates over networks), trojan (disguised as useful software), ransomware (encrypts data for payment), spyware (secretly collects activity).

Strong password rule: long, mixed case, digits, symbols, unique per site; a password manager stores them; multi-factor authentication adds a second proof.

Firewall filters network traffic by rules; antivirus scans for known malicious patterns and needs updated signatures.

Encryption converts plaintext to ciphertext with a key; HTTPS, VPNs, and encrypted backups protect confidentiality in transit and at rest.

Digital footprint is the permanent trail of online activity; personal data such as address, phone, and school should not be posted publicly.

Cyberbullying is repeated harmful behaviour online; response is to save evidence, block/report, and inform a trusted adult or authority.

Cyber law in India: the Information Technology Act, 2000 covers offences such as unauthorised access and identity theft; copyright law protects creative work.

Artificial Intelligence: systems performing tasks needing human intelligence; Machine Learning learns patterns from data instead of explicit rules.

Cloud computing delivers computing as a service: IaaS (infrastructure), PaaS (platform), SaaS (software); access is over the Internet on a pay-per-use model.

IoT connects everyday devices with sensors and network links to collect and exchange data (smart meters, wearables, smart agriculture).

Blockchain is a distributed, append-only ledger of linked blocks secured by hashes; it underlies cryptocurrencies and tamper-evident records.

Big Data is characterised by volume, velocity, variety (plus veracity, value); analytics extracts patterns from large datasets.

AR overlays digital content on the real world (phone camera); VR replaces the real view with a simulated environment, usually via a headset.

5G offers higher speed and lower latency than 4G, enabling real-time applications; edge computing processes data near the source to cut delay.

e-Governance uses IT for public services (online certificates, digital payments, Aadhaar-linked services); e-commerce covers online buying and selling.