Punjab PSEB Matric Computer Science cheat sheet

Working cycle: input devices feed raw data, the CPU processes it, output devices present the result, and secondary storage keeps data permanently after power-off.

Memory units: 8 bits = 1 byte, 1024 bytes = 1 KB, 1024 KB = 1 MB, 1024 MB = 1 GB, 1024 GB = 1 TB; a nibble is 4 bits.

Speed ladder, fastest first: CPU registers, then cache, then RAM, then SSD/hard disk, then optical disc; cache sits between the CPU and RAM to cut waiting time.

RAM is volatile and read/write, holding the programs currently running; ROM is non-volatile and read-only, holding boot firmware, with PROM, EPROM and EEPROM as its types.

The CPU has three functional blocks: the ALU does arithmetic and logical comparisons, the Control Unit fetches and decodes instructions, and registers hold data temporarily; clock speed is in GHz.

Impact printers such as dot matrix strike an inked ribbon against paper and can produce carbon copies; non-impact printers (inkjet, laser) are quieter, and laser gives the highest speed and quality.

Measurement units: printer resolution in dpi, printer speed in ppm, monitor resolution in pixels, clock speed in hertz, storage capacity in bytes.

Software is split into system software (operating system, device drivers, utilities) and application software (word processor, spreadsheet, browser, media player).

Core OS jobs: process management, memory management, file management, device management, and providing the user interface plus access security.

Windows filename rule: a name of up to 255 characters followed by an extension after the last dot - .docx document, .xlsx workbook, .pptx slides, .exe program, .jpg image, .mp3 audio.

An absolute path starts at the root, as in C:\Users\Ravi\notes.txt; a relative path starts at the current folder, and ..\notes.txt means one folder level up.

Wildcards: ? stands for exactly one character and * stands for any number of characters, so report?.docx matches report1.docx but not report10.docx.

Folder structure is a tree with one root per drive; every file has exactly one parent folder, and a folder may hold both files and subfolders.

Delete moves an item to the Recycle Bin and it can be restored; Shift+Delete removes it permanently without using the bin.

Shortcuts: Ctrl+C copy, Ctrl+X cut, Ctrl+V paste, Ctrl+Z undo, Ctrl+A select all, Alt+Tab switch windows, Alt+F4 close window, Ctrl+Shift+Esc open Task Manager.

OS types by use: single-user (MS-DOS), multi-user (Linux server), real-time RTOS for embedded control, batch, time-sharing, and distributed across networked machines.

The default Word file extension is .docx, the older binary format is .doc, and a template is saved as .dotx.

Font size and line spacing are measured in points, where 1 point = 1/72 inch, so 12-point text is 12/72 inch high.

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

Character shortcuts: Ctrl+B bold, Ctrl+I italic, Ctrl+U underline; Ctrl+Z undo, Ctrl+Y redo, Ctrl+F find, Ctrl+H replace, Ctrl+A select all.

File and proofing shortcuts: Ctrl+S save, Ctrl+P print, Ctrl+N new document, F7 spelling and grammar check, Shift+F7 thesaurus.

A header prints in the top margin of every page and a footer in the bottom margin; they are set once per section and commonly carry page numbers.

Mail merge needs exactly two parts: the main document containing fixed text and merge fields, plus the data source containing the records such as names and addresses.

Page setup controls margins, orientation (portrait is taller than wide, landscape is wider than tall) and paper size such as A4.

A cell address is column letter plus row number, so B7 means column B, row 7; the Name Box displays the address of the active cell.

Every formula begins with = and uses the operators + - * / ^ along with comparison operators =, <>, >, <, >=, <=.

Evaluation order: brackets first, then exponent, then multiplication and division, then addition and subtraction, left to right at the same level.

Relative reference A1 shifts when copied; absolute $A$1 stays fixed; mixed A$1 locks the row and $A1 locks the column; the F4 key cycles through these forms.

Core functions: =SUM(range), =AVERAGE(range), =MAX(), =MIN(), =COUNT() counts numeric cells, =COUNTA() counts non-empty cells, =ROUND(number, digits), =IF(test, value_if_true, value_if_false).

Error values: #DIV/0! for division by zero, #NAME? for an unrecognised name, #REF! for a deleted reference, #VALUE! for the wrong data type, and ##### when the column is too narrow.

Chart choice: column or bar for comparing values, line for a trend over time, pie for parts of one whole where slices total 100 percent.

Sorting rearranges rows by a chosen key column; filtering hides rows that fail a condition without deleting any data.

Freeze Panes keeps selected rows or columns visible while scrolling, and the fill handle copies formulas or extends a series.

The default extension is .pptx, a .ppsx file opens straight in slide-show mode, and a template fixes the colour scheme, fonts and layouts.

The Slide Master stores the design and placeholder positions for every slide; any edit made on the master applies to all slides that use it.

Views: Normal for editing one slide, Slide Sorter for rearranging thumbnails, Notes Page for speaker notes, Slide Show for full-screen delivery.

A transition is the effect between two slides, while an animation is the effect applied to a single object inside one slide.

F5 starts the show from the first slide, Shift+F5 starts from the current slide, Esc ends the show, and B blanks the screen to black.

Shortcuts and tools: Ctrl+M inserts a new slide, Ctrl+D duplicates a slide, Ctrl+Z undoes, and Rehearse Timings records how long each slide is displayed.

Multimedia means combining text, graphics, audio, video and animation; each inserted clip can be set to start on click or automatically.

Colour depth: 8-bit gives 256 colours and 24-bit true colour gives 16,777,216 colours; image size is measured in pixels and print quality in dpi.

URL anatomy is protocol://domain/path; HTTPS uses port 443 and encrypts traffic, while HTTP uses port 80 and sends plain text.

Protocols by job: HTTP/HTTPS for web pages, FTP for file transfer, SMTP for sending mail, POP3 and IMAP for receiving mail.

IPv4 is a 32-bit address written in dotted decimal such as 192.168.1.1; IPv6 is 128-bit and written in hexadecimal groups.

Email fields: To for the main recipient, Cc for a visible copy, Bcc for a hidden copy, plus Subject, Body and Attachment; every address has exactly one @ separating user name and domain.

Email is store-and-forward: the sender's mail server passes the message to the recipient's server using SMTP, and the recipient collects it with POP3 or IMAP.

Malware types: a virus needs a host file, a worm self-replicates across networks, a trojan disguises itself as useful software, spyware steals data, ransomware encrypts files for payment.

Phishing signs: urgent threats, a sender address that does not match the display name, unexpected attachments, link text that differs from the real URL, and any request for an OTP or password.

Safety practice facts: the https padlock with a valid certificate indicates encryption, two-factor authentication blocks password-only logins, a firewall filters traffic, and online fraud is reported at cybercrime.gov.in or the local police cyber cell.