Tamil Nadu HSE First Year Computer Applications cheat sheet

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

Data flow order: Input → Processing (CPU) → Output, with memory holding both data and instructions.

CPU parts: ALU performs arithmetic and logic; Control Unit fetches, decodes and directs; registers hold current operands.

Memory hierarchy by speed: registers > cache > RAM > secondary storage; RAM is volatile, ROM is non-volatile.

Decimal to binary: repeatedly divide by 2 and read remainders bottom-to-top; binary to decimal: sum of bit × 2^position.

Octal ↔ binary uses 3-bit groups; hexadecimal ↔ binary uses 4-bit groups; group from the radix point outward.

1 KB = 2^10 bytes = 1024 bytes, 1 MB = 2^20 bytes, 1 GB = 2^30 bytes, 1 TB = 2^40 bytes.

Signed numbers: 1's complement inverts all bits; 2's complement = 1's complement + 1; subtraction A − B = A + 2's complement of B.

BCD encodes each decimal digit in 4 bits; ASCII uses 7 bits (128 codes); Unicode supports multilingual scripts.

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

Batch, time-sharing, real-time, distributed and mobile are OS types; real-time OS must meet fixed deadlines.

Single-user vs multi-user and single-tasking vs multitasking are independent classifications.

GUI uses icons, windows and mouse; CLI uses typed commands; both are user interfaces, not OS types.

System software = OS, language translators, loaders, linkers, utilities; application software solves user tasks.

Compiler translates the whole program before execution; interpreter translates and runs line by line; assembler handles mnemonics.

Open source software provides source code for modification (e.g., Linux); proprietary software restricts it through licence.

Booting loads the OS: cold boot starts from power-off, warm boot restarts a running system; the bootstrap loader runs first.

Virtual memory uses secondary storage to extend RAM; thrashing occurs when page swapping dominates execution time.

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

Font size is measured in points (1 point = 1/72 inch); bold, italic and underline are character-level formats.

Alignment options: left, right, centre and justify; justify adjusts spacing so both margins are flush.

Header and footer repeat on every page; page numbers are inserted as fields inside them.

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

Spell check compares words against a dictionary; grammar check examines sentence structure.

Tables organise data in rows and columns; cells can merge, split and be formatted independently.

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

Save (Ctrl+S) overwrites the existing file; Save As creates a new file name or location; .docx is the standard Word format.

A cell address combines column letter and row number (e.g., B5); a range is written with a colon (A1:C10).

Formulas begin with = and use operators + − * / ^; cell references update when copied, unless made absolute with $.

$A$1 is absolute, A$1 is row-absolute, $A1 is column-absolute; F4 cycles through these reference types.

Functions: =SUM(range), =AVERAGE(range), =MAX(), =MIN(), =COUNT() counts numbers, =COUNTA() counts non-empty cells.

=IF(condition, value_if_true, value_if_false) makes decisions; conditions use =, <, >, <=, >=, <>.

Relative reference A1 shifts by the copied offset; absolute reference $A$1 stays fixed.

Charts: column for comparison, line for trends over time, pie for parts of a whole, scatter for correlation.

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

#DIV/0! means division by zero or an empty divisor; #REF! means the referenced cell was deleted.

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

Slide Master controls fonts, colours and background for all slides at once; changing it updates every slide using it.

Normal, Slide Sorter, Notes Page and Slide Show are standard views; Slide Sorter reorders and hides slides.

Transitions apply between slides; animations apply to objects inside one slide; both can set speed and triggers.

Multimedia elements: text, graphics (bitmap or vector), audio, video and animation.

Bitmap images store pixels and lose quality when enlarged; vector graphics store shapes and scale without loss.

Common formats: .jpg and .png for images, .mp3 and .wav for audio, .mp4 and .avi for video, .gif for simple animation.

Slide Show (F5) starts from the first slide; Shift+F5 starts from the current slide.

Handouts print several slides per page; notes pages print the slide plus speaker notes.

Network by size: PAN (personal), LAN (building), MAN (city), WAN (country/global); the Internet is the largest WAN.

Topologies: star uses a central hub, bus uses one backbone cable, ring is a closed loop, mesh links nodes directly.

LAN media include twisted pair, coaxial and fibre optic; fibre carries data as light and resists interference.

Protocols: TCP/IP is the Internet suite, HTTP transfers web pages, FTP transfers files, SMTP sends mail, POP3/IMAP receive it.

IP address identifies a device; IPv4 is 32-bit dotted decimal, IPv6 is 128-bit hexadecimal.

DNS converts domain names to IP addresses; a URL contains protocol, domain, path and file name.

A hub broadcasts to all ports; a switch forwards to the destination MAC address; a router connects different networks.

Search engines index the web; a browser renders pages; a web server stores and serves them.

Bandwidth is data capacity per second; a modem modulates and demodulates signals over telephone lines.

Problem-solving steps: analyse the problem, design the algorithm, code it, test it, then document and maintain it.

An algorithm is a finite, unambiguous sequence of steps; a flowchart draws it with standard symbols.

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

Pseudocode uses structured English without language-specific syntax; indentation shows blocks.

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

A variable is a named memory location that can change; a constant keeps one fixed value.

A trace table records variable values after each step and is used to dry-run an algorithm by hand.

Desk checking verifies logic manually; debugging locates and removes errors in a running program.

Error types: syntax (rule violation), logical (wrong result), runtime (fails during execution, e.g., division by zero).

Data types: int (whole numbers), float (decimals), char (one character), string (text), bool (true/false).

Arithmetic operators + − * / and modulus %; % returns the remainder, so 17 % 5 = 2.

Relational operators ==, !=, <, >, <=, >= return true or false; = assigns, == compares.

Logical operators: AND is true only if both operands are true; OR is true if either is true; NOT inverts.

if executes a block when the condition is true; if-else chooses between two blocks; else-if chains multiple tests.

for loop suits a known count; while tests the condition before each iteration; do-while tests after, so it runs at least once.

break exits a loop immediately; continue skips the rest of the current iteration and goes to the next.

Nested loops run the inner loop fully for each outer iteration; total iterations = outer × inner.

Arrays store many values of one type under one name, indexed from 0 in most languages.

HTML structure: contains (title, meta) and (visible content).

Headings run

makes a paragraph;
forces a line break;

Lists:

unordered (bullets),
ordered (numbers), definition list; each item uses
1. .

text creates a hyperlink; embeds an image, with alt as fallback text.

// are presentational tags; CSS separates style from structure via inline, internal or external style sheets.

Attributes always appear in the opening tag as name="value" pairs; tags are case-insensitive but lowercase is conventional.

Empty (void) elements such as
,

A DBMS stores, retrieves and manages data; a table (relation) holds rows (records) and columns (fields).

Primary key uniquely identifies each row and cannot be null; foreign key references a primary key in another table.

Candidate keys are all possible unique identifiers; one is chosen as the primary key.

Data types: CHAR fixed length, VARCHAR variable length, INT, DATE, DECIMAL.

SELECT column FROM table WHERE condition retrieves rows; WHERE filters before grouping.

DISTINCT removes duplicate rows; ORDER BY sorts ascending (ASC) or descending (DESC).

Aggregate functions: COUNT, SUM, AVG, MAX, MIN; GROUP BY groups rows for these functions, HAVING filters groups.

INSERT INTO adds rows, UPDATE modifies them, DELETE removes them, and DROP removes the whole table structure.

Normalisation reduces redundancy: 1NF removes repeating groups, 2NF removes partial dependence, 3NF removes transitive dependence.