Unit 8: Information and Communication Technology mind map

Hardware, memory and storage units, generations of computers, and the classic acronyms.

Hardware and the CPU

CPU, input and output

The CPU has two main parts. Input devices send data in; output devices send results out.

• CPU: control unit and arithmetic logic unit (ALU).
• The CPU runs a fetch-decode-execute-store cycle.
• Input: keyboard, mouse, joystick, digitiser, touch pad, MICR, OMR.
• Output only: plotter, projector, speaker, printer, monitor.

Read 'only' in the stem. A scanner and light pen feed data in, so they are not output only. DVD-R is storage, so it is not input only. A touch screen accepts touch but also displays output. Clock speed is measured in hertz.

Printers and display terms

Impact printers strike the paper. Non-impact printers do not.

• Laser printer is non-impact: laser, drum, toner, heat.
• Dot matrix, daisy wheel and line printers are impact.
• Dot matrix printers are noisy, slow and coarse.
• VDU is Visual Display Unit. DPI is dots per inch.

Ask whether a physical part hits the page. If yes, impact. Printer resolution is measured in dots per inch, and CRT is cathode ray tube.

Acronyms that keep returning

Learn the expansions asked again and again.

• BIOS: Basic Input Output System, firmware on the motherboard.
• PDF: Portable Document Format. WORM: Write Once Read Many.
• ARPANET: Advanced Research Project Agency Network.
• HTTPS: Hypertext Transfer Protocol Secure, not Standard.

Distractors change one word, so read the options slowly. CMOS is complementary metal oxide semiconductor, not consistent. NIC is network interface card. MAC is Media Access Control.

Memory and storage units

Units and conversions

Memory units rise in steps of 1,024.

• 1 KB = 1,024 bytes. 1 TB = 1,024 GB.
• Bit, nibble (4 bits), byte (8 bits), KB, MB, GB, TB.
• 960 KB = 960 x 1,024 bytes.
• Divide by 1,024 when the question says 1k = 1024.

Two hours of video at 180 MB a minute is 120 x 180 = 21,600 MB, which is 21.1 GB. One image every 5 seconds for 24 hours is 17,280 images, so 16.875 GB at 1 MB each.

Primary memory, ROM and RAM

RAM is fast, volatile working memory. ROM keeps its contents without power.

• RAM can be read and written. More RAM can improve performance.
• ROM holds start-up instructions and is called firmware.
• Volatile: RAM, cache, CPU registers. Flash and hard disk are not.
• Primary storage is faster and more expensive per unit, and not persistent.

In decreasing speed the order runs registers, cache, RAM, SSD, hard disk. ROM is not temporary. EPROM is erased by ultraviolet light. Reading ROM never changes it.

Storage devices and classes of computers

Order devices by capacity, and computers by power or size.

• Capacity: CD-ROM about 700 MB, DVD-ROM about 4.7 GB, hard disc hundreds of GB.
• Processing power, high to low: supercomputer, mainframe, mini, micro.
• Size, small to large: tablet, notebook, desktop, minicomputer.
• Hard disc stores the most among CD, floppy and magneto-optical.

A minicomputer is a cabinet-sized mid-range machine despite its name. A floppy disc holds only 1.44 MB.

History of computing

Generations

Each generation replaced the switching element with a smaller one.

• First: vacuum tubes. Second: transistors.
• Third: integrated circuits. Fourth: microprocessor.
• Fourth generation began from 1971 and made the personal computer possible.
• Order: vacuum tube, transistor, IC, microprocessor.

A microprocessor is a whole CPU on one chip. ENIAC and UNIVAC were first-generation machines.

People and milestones

Match each person to the idea.

• John von Neumann: stored-program concept, around 1945.
• Douglas Engelbart: first computer mouse, shown in 1968.
• Tim Berners-Lee: World Wide Web, 1989.
• Operating system evolution: batch, single user single task, multiprocessing, real-time.

The Web is a system of interlinked hypertext documents. The Internet is the underlying network, and it began with ARPANET in 1969.

Binary, octal, decimal and hexadecimal: conversion, ordering and addition.

Base conversion

Any base to decimal

Expand by place value. Each digit times the base to its position.

• (3013) base 4 = 3x64 + 0x16 + 1x4 + 3 = 199.
• (9C) base 16 = 9x16 + 12 = 156.
• (233) base 8 = 155. (313) base 7 = 157.
• Do not skip a zero digit.

A skipped zero shifts every later digit one place. Hex digits A to F are 10 to 15, so B is 11 and D is 13.

Decimal to another base

Divide again and again by the base. Read the remainders from the bottom.

• Check by expanding: 2x36 + 4x6 + 4 = 100.
• 75 in binary = 64 + 8 + 2 + 1 = 1001011.
• 50 = 32 + 16 + 2 = 110010.

For binary, break the number into powers of two and write 1 where a power is used. The question may give a nearby number, such as 53 = 110101, so work by difference.

100 in base 6: 100 / 6 = 16 r 4, 16 / 6 = 2 r 4, then 2. Answer (244) base 6.

Fractions and ordering

Convert the whole part and the fraction separately, then sort.

• (10110.11) base 2 = 22.75.
• (110.2) base 4 = 20.5. (32.5) base 8 = 26.625. (14.6) base 16 = 20.375.
• Fraction digit: digit divided by base.
• Descending order here is C, A, B, D.

Many items use values very close together, such as 25.375, 25.625, 25.75 and 27.5. The fractions decide the ranking, so never ignore them.

Addition across bases

Safest way: convert to decimal, add, convert back.

• (107) base 16 + (257) base 16 = 263 + 599 = 862 in decimal.
• Check the base asked for in the options.

Direct addition also works. In octal, 4 + 5 = 9, which is 11 in base 8, so write 1 and carry 1. Use it to check.

(144) base 8 + (175) base 8 = 100 + 125 = 225 = (341) base 8.

(4AC) base 16 + (9BF) base 16 = 1196 + 2495 = 3691 = (E6B) base 16.

Which equality is true?

Convert every side in the options and test them all.

• (127.125) base 10 equals its binary, base 4, octal and hex forms.
• (BD) base 16 = 189 = (275) base 8 = (10111101) base 2.
• (123) base 5 = 38 = (212) base 4.
• (1011) base 2 + (1001) base 2 = 20 in decimal.

Do not shortlist by looks. Each wrong option fails by a small margin, and the true line may equate two non-decimal numbers. Convert both sides.

The Web, browsers, addresses, network types and topologies, transmission modes, and e-mail fields.

The Internet and the Web

Internet, Web and browsers

The Internet is the network. The Web is a system of linked documents on it.

• ARPANET began the Internet, from 1969.
• Browsers: Internet Explorer, Firefox, Chrome. Yahoo is a portal.
• Search engines: Google, Bing.
• A cookie is a small text file a browser stores about you.

A browser is application software, but 'browser' is the precise answer. HTTPS sends web data securely. A URL is the text version of a web address.

Net neutrality and social platforms

Net neutrality means all internet data is treated equally.

• Providers must not block, slow or favour content.
• Khan Academy is a learning platform, not a social network.
• Twitter, Instagram, LinkedIn, Snapchat, Facebook are social networks.
• Streaming plays video while it is still downloading.

A small start-up's video travels on the same terms as a large company's. LinkedIn is a professional network.

Networking

Addresses

IP identifies a host. MAC identifies the network card.

• IPv4 is 32 bits. IPv6 is 128 bits, four times longer.
• MAC is 48 bits, six pairs of hex digits, for example F8:FC:AE:7B:16:CE.
• MAC stands for Media Access Control.
• IPv6 gives 2 to the power 96 times as many addresses.

Count the pairs. Only an address with six pairs is a valid MAC. The answer (P, Q) = (32, 128) is the most examined pair in this topic.

Network types and topologies

Networks differ by coverage. Topologies differ by layout.

• Coverage, small to large: PAN, LAN, MAN, WAN.
• Topologies: bus, star, ring, mesh, tree, hybrid. Chain is not a topology.
• Star: every device links to a central node.
• Star weakness: if the central node fails, everything stops.

A PAN covers about ten metres around one person. A LAN covers a building or campus. A MAN covers a city. A WAN covers a country or the world.

Modem, packets and transmission modes

A modem modulates and demodulates. Packet switching sends independent packets.

• Modem converts digital to analogue and back.
• Packets may take different routes and arrive out of order.
• Simplex: one way. Half-duplex: both ways, one at a time. Full-duplex: both at once.
• Radio and TV broadcast, and a keyboard: simplex. Walkie-talkie: half-duplex. Telephone: full-duplex.

Receiving ends reassemble packets using sequence numbers. The wrong option for packet switching is that packets always follow the same route.

E-mail

To, Cc and Bcc

To and Cc recipients are visible to each other. Bcc recipients are hidden.

• Bcc stands for blind carbon copy.
• Bcc hides the address from other recipients.
• SMTP sends mail. POP3 and IMAP receive it.

In the birthday-party example, Rohan cannot know that John, who was on Bcc, received the mail. Bcc is useful for privacy when mailing many unknown people.

Malware types, phishing, keyloggers, firewalls and cyber law.

Malware and attacks

Types of malware

Match each malware to what it does.

• Virus: self-replicating malicious code.
• Worm: copies itself across a network without user action.
• Trojan horse: looks useful, does damage once run; does not spread by itself.
• Spyware: secretly records what the user does. Ransomware: locks data and demands payment.

A keylogger is a form of spyware. A logic bomb triggers when a condition occurs, and a time bomb at a set time. A trapdoor or backdoor is code left for later unauthorised access. A polymorphic virus changes its appearance. A rootkit hides itself deep in the system. A macro virus hides in document macros.

Phishing and other attacks

Phishing tricks people into giving away sensitive data.

• Attacker pretends to be a trusted organisation, often by fake e-mail.
• Risk to the user: fraudulent activity.
• Denial-of-service stops access to a site; spyware does not.
• Capturing keyboard entries is keylogging, not a DoS attack.

In a June 2023 item the statements swapped these jobs, so only 'virus is self-replicating malicious code' was right. India is not a signatory to the Budapest Convention on Cybercrime, a point asked in June 2025.

Firewalls and safe practice

A firewall protects a network from unauthorised access.

• It inspects traffic against rules.
• It sits between a trusted and an untrusted network.
• A cookie is a text file in your browser, not a security tool.
• A fake virus warning is a hoax.

The word 'unauthorised' is what the firewall answer turns on. Mason's PAPA lists the main IT ethics issues: privacy, accuracy, property, accessibility.

Cell references, copying formulas, and the IF, COUNTIF, SUMIF and lookup functions.

Cell references

Absolute, relative and mixed

A dollar sign freezes the part after it when a formula is copied.

• $E$5: absolute. Column and row fixed.
• E$5: mixed, row fixed. $E5: mixed, column fixed.
• E5: relative; both change.
• Copying moves a relative part by the same number of rows and columns.

=B$1 + C$3 + 5 in D9, copied to F12, moves 2 columns and 3 rows. Columns shift, the fixed rows stay, so it becomes =D$1 + E$3 + 5. To fix an hourly rate in B1 while copying down, write =$B$1*B4.

Reading a copied formula

Rewrite the formula for the new cell, then read the value.

• Cell B2: =A2+$B$1 with B1 = 16. Copied to B3 it becomes =A3+$B$1.
• If A3 = 8, B3 = 8 + 16 = 24.
• =$A$3+B2 copied one row down becomes =$A$3+B3.
• An empty cell counts as zero.

Absolute parts never move. Relative parts move with the copy. If the moved reference lands on a blank cell, treat it as 0, giving 7 + 0 = 7 in the June 2022 item.

Functions

IF, COUNTIF, SUMIF and lookups

Know what each function returns and the order of its arguments.

• IF(test, value if true, value if false).
• COUNTIF counts cells that meet a condition. COUNTIFS uses many.
• SUMIF adds cells that meet a condition. SUMIFS uses many.
• VLOOKUP searches down a column; HLOOKUP searches along a row.

=IF(A2<=100,"Within Budget","Over Budget") matches the rule of printing Within Budget when A2 is 100 or less. Excel statistical functions: AVERAGE gives the mean, COUNT the number of entries, MEDIAN the middle value, MODE the most frequent.

System and application software, open source, and the tools teachers use online.

Kinds of software

System and application software

System software runs the machine. Application software does a user task.

• System: Windows, Linux, Android, iOS, DOS.
• Application: MS Excel, Photoshop, browsers, Office, OpenOffice.
• Microsoft Windows is not part of Microsoft Office.
• A language translator is an assembler, compiler or interpreter; a codec is not.

When the stem says application software ONLY, drop every operating system. Compiler translates the whole program at once; interpreter works line by line.

Shareware, freeware, open source

Licence type decides what you may do.

• Shareware: free trial, limited, expires, no source code changes.
• Freeware: free to use as long as you like.
• Open source: distributed with source code, which may be modified.
• Linux is the standard open source example.

Statement 'Shareware code can be modified and redistributed' is false. Open source does not by itself guarantee security or speed. The (cc) symbol means Creative Commons.

Tools for teaching

Match the tool to the task

Each tool is built for one classroom job.

• LMS: Moodle, Canvas, Blackboard, Schoology, Edmodo. Zoom and Strawpoll are not LMS.
• Edpuzzle: video with embedded questions.
• Kahoot: game quizzes. Padlet: shared wall. Mentimeter: polls and surveys.
• Labster and PhET: virtual labs and simulations.

Camtasia records, edits and shares screen video. Trello manages projects. Turnitin checks copied text. Google Earth gives virtual field trips. Poll Everywhere collects live answers.

Mind maps, video and curation

Special-purpose tools asked directly.

• Mind maps: MindMeister, XMind, CMap, Coggle, Miro.
• Flip (Flipgrid): short video responses.
• Wakelet: collect and curate content.
• A-VIEW: virtual classroom tool from Amrita University.

Screencast-O-Matic records the screen and Photoshop edits images, so neither is a mind-mapping tool. Canva and Book Creator build visual presentations with video.

MOOCs and online learning

A MOOC is massive, open and online. The four-quadrant format organises it.

• Quadrant I video lectures. II reading material.
• Quadrant III self-assessment. IV discussion forum.
• Massive means a huge number of learners can enrol.
• Discussion forum links learners and course coordinators.

MOOCs use ICT to reach students in remote areas. The older name for Flip is Flipgrid.

Government platforms, SWAYAM Prabha channels, and new technologies like RFID, quantum computing and AI.

Government platforms

Digilocker, NAD, e-ShodhSindhu

Know what each government platform does.

• Digilocker: digital locker for documents, linked to Aadhaar; slogan 'Your documents anytime, anywhere'.
• National Academic Depository: online store of certificates, degrees and marksheets.
• e-ShodhSindhu: merges UGC-INFONET, NLIST and INDEST-AICTE.
• Saransh: CBSE decision support system.

Helping young entrepreneurs is Startup India, not Digilocker. The wrong Digilocker option changed the slogan to 'My documents'. BHIM is an NPCI app built on UPI. Scopus is a database of abstracts and citations.

SWAYAM and SWAYAM Prabha

SWAYAM Prabha is a set of DTH education channels.

• Channel 04 Saaraswat. 05 Prabandhan. 06 Vidhik. 07 Kautilya. 08 Aryabhatta.
• Channels 1, 3 and 6 under CEC, New Delhi.
• Channels 11 and 15 under IGNOU; 15 is Capacity Building and Teacher Education.
• Channel 20 belongs to an IIT (NPTEL).

Prabandhan is management, Vidhik legal studies, Kautilya economics. Channels 4 and 7 are CEC channels. The key follows the paper in front of you.

Emerging technology

RFID, quantum, 3D printing, OLED

Short facts on new technologies.

• RFID: Radio Frequency Identification, a microchip and antenna in a tag.
• RFID bands: low (125 kHz), high (13.56 MHz), ultra high.
• Quantum computing uses qubits.
• 3D printers build objects from CAD designs; OLEDs make their own light.

RFID is not a biometric method. OLEDs generally use less power than LCD or LED. Quantum computers do not emit fatal radiation. A wearable fitness tracker is not WiMAX.

ICT and society

ICT brings both gains and gaps.

• Digital divide: gap between those with access and those without.
• It can arise from income, location, age, education or gender.
• A blog is a form of social media.
• Digital India does not promise free Wi-Fi to every citizen.

Digital India aims at broadband highways, mobile connectivity and e-governance. Cloud storage allows access from any device anywhere.