Assam ASSEB HSLC Elective Computer Science cheat sheet

Computer = input → process → output → storage; IPO plus storage is the standard functional model.

Hardware is physical; software is instructions. Data is raw facts; information is processed data with meaning.

Memory units: 1 byte = 8 bits; 1 KB = 1024 B; 1 MB = 1024 KB; 1 GB = 1024 MB; 1 TB = 1024 GB.

Decimal to binary: divide repeatedly by 2 and read remainders bottom-to-top. Binary to decimal: sum bit × 2^position, positions counted from 0 at the right.

Binary to octal: group 3 bits from the right; binary to hexadecimal: group 4 bits from the right; pad the leftmost group with zeros.

1's complement = flip all bits; 2's complement = flip all bits then add 1. Subtraction A − B = A + 2's complement of B, discarding the final carry.

Octal digits are 0–7, hexadecimal digits are 0–9 and A–F (A = 10 … F = 15).

Character codes: ASCII uses 7 bits (128 characters); extended ASCII uses 8 bits (256). BCD encodes each decimal digit in 4 bits.

Generations: 1st vacuum tubes, 2nd transistors, 3rd integrated circuits, 4th microprocessors, 5th AI/ULSI.

CPU parts: ALU (arithmetic and logic), Control Unit (fetch–decode–execute control), and registers (fast internal storage).

Primary memory is directly accessed by the CPU (RAM, ROM, cache); secondary memory is permanent storage (HDD, SSD, pen drive, optical disc).

RAM is volatile and read/write; ROM is non-volatile. SRAM uses flip-flops and is faster; DRAM uses capacitors and needs refreshing.

Input devices: keyboard, mouse, scanner, microphone, joystick, light pen, OMR/OCR/barcode reader. Output: monitor, printer, plotter, speaker.

Impact vs non-impact printers: dot matrix is impact (carbon copies possible); inkjet and laser are non-impact. Laser is fastest and highest quality.

System software = OS, device drivers, utilities, language translators. Application software = general purpose (word processor) or specific purpose (payroll).

OS functions: process management, memory management, file management, device management, and providing a user interface.

Types of OS: batch, multiprogramming, multitasking, time-sharing, real-time, distributed, and network OS.

Compilers translate the whole program before running; interpreters translate line by line; assemblers translate assembly language to machine code.

GUI elements: desktop, icons, taskbar, Start menu, window, dialog box, pointer, and cursor.

Window controls: minimize (–) hides to taskbar, maximize (□) fills the screen, restore returns to previous size, close (×) ends the program.

Keyboard shortcuts: Ctrl+C copy, Ctrl+X cut, Ctrl+V paste, Ctrl+Z undo, Ctrl+Y redo, Ctrl+A select all, Ctrl+S save, Ctrl+P print, Alt+F4 close window, Alt+Tab switch windows.

File name rules in Windows: up to 255 characters, cannot contain \ / : * ? " < > |; extension identifies the file type.

Common extensions: .txt text, .docx Word, .xlsx Excel, .pptx PowerPoint, .exe executable, .jpg image, .mp3 audio, .zip compressed.

A folder holds files and subfolders; the path (e.g., C:\Users\Name\Docs) shows the location. Recycle Bin stores deleted items until emptied.

Right-click opens the context menu; double-click opens an item; drag-and-drop moves (same drive) or copies (different drive) files.

File attributes: read-only, hidden, archive, system. Wildcards: * matches any number of characters, ? matches exactly one.

Disk cleanup, defragmentation, and formatting are maintenance operations performed through system tools.

Word wrap automatically moves text to the next line; Enter starts a new paragraph, Shift+Enter inserts a line break.

Alignment: left, center, right, justify. Justify stretches spacing so both margins are even.

Font formatting changes appearance (typeface, size in points, bold, italic, underline, color); paragraph formatting changes layout (alignment, indent, spacing, line spacing).

Ctrl+B bold, Ctrl+I italic, Ctrl+U underline, Ctrl+E center, Ctrl+L left, Ctrl+R right, Ctrl+J justify.

Header appears at the top of every page; footer at the bottom. Page numbering is inserted through the header/footer area.

Find (Ctrl+F) locates text; Find and Replace (Ctrl+H) substitutes text throughout the document.

A table is a grid of rows and columns; cells can be merged or split, and borders/shading control appearance.

Mail merge combines a main document with a data source to produce many personalized copies.

Save (Ctrl+S) overwrites the existing file; Save As creates a new file with a chosen name, location, or format (e.g., .pdf).

A workbook contains worksheets; each worksheet is a grid of columns (A, B, C…) and rows (1, 2, 3…); the intersection is a cell (e.g., B5).

A range is written with a colon, e.g., A1:C10. The active cell is the one currently selected.

Every formula begins with = ; arithmetic operators are + − * / ^ and % .

Relative reference (A1) changes when copied; absolute reference ($A$1) stays fixed; mixed references lock only the row ($A1) or column (A$1).

SUM(range) adds, AVERAGE(range) gives the mean, MAX/MIN return extremes, COUNT counts numeric cells, COUNTA counts non-empty cells.

IF(condition, value_if_true, value_if_false) makes decisions; COUNTIF and SUMIF apply conditions to ranges.

Common errors: #DIV/0! division by zero, #REF! invalid reference, #NAME? unrecognized name, #VALUE! wrong data type, ##### column too narrow.

Charts: column/bar compare values, line shows trends over time, pie shows parts of a whole (single data series).

Sorting arranges data by a key; filtering hides rows that do not match a condition without deleting them.

A presentation is a file of slides; a slide layout defines placeholder positions for title, text, and objects.

Slide views: Normal (edit), Slide Sorter (reorder), Notes Page (speaker notes), Slide Show (present), Reading view.

Transitions apply between slides; animations apply to objects within a slide. Too many of either reduce clarity.

Slide Master controls the common design (fonts, background, placeholders) for all slides at once.

F5 starts the slide show from the beginning; Shift+F5 starts from the current slide; Esc ends the show.

During a show: N or Enter or Space = next, P or Backspace = previous, B = black screen, W = white screen, number + Enter = jump to slide.

Templates provide a ready-made design; themes control colors, fonts, and effects consistently.

Insert options include text box, picture, chart, table, SmartArt, audio, and video.

Save As can export to PDF or image formats; slide size (4:3 or 16:9) should be set before designing.

Internet = global network of networks; WWW = hyperlinked documents accessed through it; a browser is the client software.

URL parts: protocol (https://), domain name, path, and resource. HTTP/HTTPS transfer web pages; HTTPS is encrypted.

IP address identifies a device; IPv4 is 32-bit (four dotted decimal numbers), IPv6 is 128-bit. DNS translates domain names into IP addresses.

Search operators: quotation marks for an exact phrase, minus sign to exclude a word, site: to restrict to one domain.

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

Email etiquette: clear subject line, short paragraphs, no ALL CAPS, check attachments before sending, reply vs reply-all chosen deliberately.

Protocols: SMTP sends mail, POP3/IMAP retrieve mail, FTP transfers files, HTTP/HTTPS serves web pages.

Top-level domains: .com commercial, .org organization, .net network, .edu education, .gov government, .in country code for India.

A cookie is a small file a website stores on the client to remember state; cache stores copies of pages for faster reload.

Algorithm = finite, ordered, unambiguous steps to solve a problem; a flowchart draws it with standard symbols.

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

Three control structures: sequence (steps in order), selection (if/if-else), iteration (loops such as for and while).

Variable = named memory location whose value can change; constant does not change; a good identifier starts with a letter and contains no spaces.

Data types: integer, real/float, character, string, boolean. Assignment uses = (in pseudocode, ← is often used).

Arithmetic operators: + − * / and MOD (remainder) and integer division. Relational: = <> < > <= >=. Logical: AND, OR, NOT.

If-else chooses one of two paths; a loop repeats while a condition holds, and must change something to avoid an infinite loop.

Tracing a loop: list each variable's value per iteration to find the output. Example: sum = 0; for i = 1 to 5: sum = sum + i gives 15.

Swapping two variables needs a temporary third variable: temp = a; a = b; b = temp.

E-governance: online delivery of government services (certificates, land records, tax filing, digital identity).

E-commerce models: B2B (business to business), B2C (business to consumer), C2C (consumer to consumer).

E-banking services: ATM, NEFT/RTGS transfers, mobile banking, UPI, passbook printing, online statements.

E-learning: LMS platforms, MOOCs, video lectures, online assessments; benefits are reachability and self-paced study.

IT in health: telemedicine, electronic health records, online appointment and lab reporting systems.

IT in education and agriculture: digital libraries, weather and market-price information for farmers, online advisories.

Digital India and similar programmes aim at digital infrastructure, governance on demand, and digital literacy.

Office automation: word processing for documents, spreadsheets for accounts, databases for records, presentations for reporting.

Social media and messaging are used for awareness and business, but require verification of information before sharing.

Strong password: at least 8–12 characters mixing upper case, lower case, digits, and symbols; never reuse one password across sites.

Phishing = fraudulent email or message that imitates a trusted sender to steal credentials; check the sender address and links before clicking.

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

Firewall filters network traffic; antivirus detects and removes malware; both need regular updates.

Never share OTP, CVV, PIN, or passwords. Banks never ask for them by phone, email, or message.

Cyberbullying is repeated harmful behaviour online; the response is to not reply, save evidence (screenshots), block, and report to a trusted adult or platform.

Personal data such as address, school name, phone number, and photographs should not be posted publicly; privacy settings should be reviewed.

Digital footprint is the permanent record of online activity; digital etiquette (netiquette) means respectful, lawful behaviour online.

Report cybercrime in India through the national cybercrime portal or helpline 1930; keep evidence for any complaint.

Before starting, check that the machine, keyboard, mouse, and monitor are connected and the required software is installed.

Save work at short intervals with Ctrl+S; name files clearly (e.g., project_name_class_roll) and keep a backup copy.

Practical word processing tasks: type text, apply font and paragraph formatting, insert a table, add header/footer and page numbers, save as PDF.

Practical spreadsheet tasks: enter data, use SUM/AVERAGE/IF, create a chart, sort and filter, format cells, print with gridlines.

Practical presentation tasks: choose a theme, insert slides with title and content, add images and a chart, apply transitions, run the slide show.

Lab safety: no food or drink near the machine, shut down through the OS (not the power switch), handle pen drives only after scanning.

Shut down properly: close applications, save files, then Start → Shut down; improper shutdown can corrupt files.

A project report typically contains title page, introduction, objective, tools used, procedure, output screenshots, result, and conclusion.

Record the observation table honestly, mention the exact formulas or steps used, and keep the project file and a printed copy.