NIELIT CCC+ cheat sheet
NIELIT CCC+ · Keep the key ideas within reach.
Computer Fundamentals
Von Neumann architecture: CPU (ALU + control unit + registers), memory, input/output; data and instructions share the same memory and bus.
Memory ladder by speed and cost: registers > cache (L1/L2/L3) > RAM > SSD > HDD > optical/tape; capacity ordering is roughly the reverse.
1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB, 1 TB = 1024 GB; storage vendors may use powers of 1000, which explains 'missing' capacity.
1 byte = 8 bits; a nibble = 4 bits. Number of distinct values in n bits = 2^n, so 8 bits give 256 values (0-255 unsigned).
Unsigned binary to decimal: multiply each bit by 2^position from the right. 1101 = 8+4+0+1 = 13.
ASCII uses 7 bits (128 codes); Extended ASCII uses 8 bits (256 codes); Unicode is a character set, UTF-8 is a variable-length encoding of it.
Primary memory is volatile (RAM, loses data on power off); ROM is non-volatile firmware storage. Secondary storage is non-volatile.
Ports: USB is hot-swappable serial; HDMI carries digital audio+video; VGA is analog video only; RJ-45 is Ethernet; RJ-11 is telephone.
Software classes: system software (OS, drivers, utilities) manages hardware; application software (word processor, browser) serves user tasks.
Operating System and Word Processing
OS roles: process management, memory management, file system management, device management, and user interface (GUI or CLI).
Booting order: POST → locate boot device → load bootloader → load kernel → start services → user login.
File path rules: drive letter plus backslash on Windows (C:\Docs\a.txt); forward slash and a single root on Linux (/home/user/a.txt).
Common extensions: .docx Word document, .txt plain text, .rtf rich text, .pdf fixed layout, .csv comma-separated values.
Word shortcuts: Ctrl+S save, Ctrl+Z undo, Ctrl+Y redo, Ctrl+C/X/V copy/cut/paste, Ctrl+A select all, Ctrl+F find, Ctrl+P print.
Formatting shortcuts: Ctrl+B bold, Ctrl+I italic, Ctrl+U underline; Ctrl+E centre, Ctrl+L left, Ctrl+R right, Ctrl+J justify.
Styles in a word processor store reusable character/paragraph formatting; applying Heading styles enables automatic table of contents generation.
Find and Replace can match case and whole words only; Replace All applies every match without further prompts.
Header/footer content repeats on every page; page numbers inserted there are usually auto-fields, not typed text.
Spreadsheet and Presentation
Cell reference types: A1 relative (changes on copy), $A$1 absolute (fixed), $A1 column-locked, A$1 row-locked.
Formula always begins with '='; functions use name plus parentheses, e.g. =SUM(A1:A10), =AVERAGE(B2:B9), =COUNT(C1:C50).
=COUNTA counts non-empty cells; =COUNT counts numeric cells only; =COUNTBLANK counts empty cells.
Logical functions: =IF(condition, value_if_true, value_if_false); nest IFs or use =AND()/=OR() inside the condition.
Lookup: =VLOOKUP(lookup, table, col_index, FALSE) for exact match; FALSE/0 must be used or approximate matching may return wrong rows.
Error values: #DIV/0! divide by zero, #REF! deleted reference, #NAME? unrecognised name, #VALUE! wrong operand type, ##### column too narrow.
Sorting reorders rows; filtering hides rows without deleting them. Use absolute references before sorting formulas that point at fixed cells.
Charts: pie for parts of a whole (one series), column/bar for comparison, line for trends over time, scatter (XY) for correlation.
Slide show shortcuts: F5 start from beginning, Shift+F5 from current slide, Esc end show; slide layouts control placeholder positions.
Internet, Email and Digital Services
OSI layers bottom-up: Physical, Data Link, Network, Transport, Session, Presentation, Application; TCP/IP collapses these to four layers.
IPv4 is 32-bit dotted decimal (0-255 per octet); IPv6 is 128-bit hexadecimal. Private IPv4 ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
DNS resolves domain names to IP addresses; DHCP assigns IP configuration automatically; NAT maps private addresses to a public one.
Ports: HTTP 80, HTTPS 443, FTP 21, SMTP 25, POP3 110, IMAP 143, DNS 53, SSH 22, Telnet 23.
URL anatomy: scheme://host:port/path?query#fragment - e.g. https://example.com:443/page?id=7#top.
Email fields: To (primary recipients), Cc (visible copy), Bcc (hidden copy), Subject; attachments are encoded (MIME) and limited by server size.
SMTP sends mail; POP3 downloads and often deletes from server; IMAP keeps mail synchronised on the server across devices.
Digital payments: UPI uses a virtual payment address; QR codes encode a payment string; never share OTP, PIN, or CVV - no legitimate service asks for them.
Safe browsing signs: HTTPS plus padlock means encrypted transport, not proof of trustworthy content; verify the exact domain spelling before entering credentials.
Computer Fundamentals
CPU cycle: fetch → decode → execute → write back; clock speed in GHz sets cycles per second.
RAM is volatile working memory; cache sits between CPU and RAM to reduce average access time.
1 byte = 8 bits; n bits encode 2^n distinct values.
ASCII: 7-bit character encoding; Unicode covers most writing systems.
Input devices: keyboard, mouse, scanner, microphone; output: monitor, printer, speaker.
USB supports hot swapping; HDMI carries digital video and audio.
System software manages hardware; application software performs user tasks.
Operating System and Word Processing
OS manages processes, memory, files, and devices, and provides the user interface.
Boot sequence: POST → bootloader → kernel → services → login.
Windows paths use drive letters and backslashes; Linux uses a single root and forward slashes.
Ctrl+S saves, Ctrl+Z undoes, Ctrl+F finds, Ctrl+P prints.
Ctrl+B/I/U apply bold, italic, underline.
Styles enable automatic tables of contents.
Headers and footers repeat on every page.
Spreadsheet and Presentation
$A$1 is absolute; A1 is relative and shifts when copied.
Formulas start with '='; =SUM(A1:A10) totals a range.
=COUNT counts numbers; =COUNTA counts non-empty cells.
=IF(test, true_value, false_value) branches on a condition.
VLOOKUP with FALSE performs an exact match.
#DIV/0! means division by zero; #REF! means a deleted reference.
F5 starts a slide show from the beginning; Shift+F5 from the current slide.
Internet, Email and Digital Services
DNS maps names to IP addresses; DHCP assigns addresses automatically.
HTTPS uses port 443; HTTP uses port 80.
SMTP sends; POP3 downloads; IMAP synchronises on the server.
Bcc hides recipients from other recipients.
IPv4 is 32-bit; IPv6 is 128-bit.
A padlock indicates encryption, not content trustworthiness.
Never share OTP, PIN, or CVV with anyone.