Fundamentals of Information Technology

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Information Technology (IT) is the use of computers, networks, and software to store, process, retrieve, and transmit information; a computer is an electronic device that accepts data as input, processes it under the control of a stored program, and produces meaningful output.

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Key characteristics: Speed (performs millions of instructions per second, measured in MIPS/GHz), Accuracy (error-free results only if input and instructions are correct), and Diligence (repetitive tasks performed without fatigue or loss of accuracy).

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Further characteristics: Storage capacity (stores huge volumes of data permanently, recalls it instantly), Versatility (performs very different tasks by simply changing the program), and Automation (runs without continuous human intervention once started).

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A computer has No IQ / No feelings — it only follows instructions; it cannot think, judge, or feel on its own (zero intelligence quotient of its own).

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Evolution — early mechanical aids: Abacus (~3000 BC, beads on rods, earliest known manual calculating device), Napier's Bones (1617, rods for multiplication/division using logarithms), Pascaline (1642, Blaise Pascal's mechanical gear-driven adding machine), Stepped Reckoner (1671, Leibniz's calculator — could add, subtract, multiply, divide).

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Difference/Analytical Engine (1822/1837) — Charles Babbage's designs; the Analytical Engine had a store, mill, and punched-card input, the conceptual ancestor of the modern computer; Babbage is called the 'Father of the Computer'.

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Tabulating Machine (1890) — Herman Hollerith's punched-card machine used for the US census; ENIAC/EDVAC/UNIVAC (1940s) were the first electronic computers, and EDVAC introduced the stored-program concept (von Neumann architecture).

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Block diagram: Input Unit (keyboard, mouse, scanner) accepts data/instructions and converts them to machine-readable form; Output Unit presents processed results (monitor, printer, speaker); Memory Unit is primary storage holding data/instructions currently in use.

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Central Processing Unit (CPU) is the 'brain' of the computer — consists of the ALU (Arithmetic Logic Unit, performs arithmetic & logical operations), the Control Unit (CU) (directs and coordinates all operations), and Registers (small, high-speed storage). Data flow: Input → CPU (Memory + ALU + CU) → Output.

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Generations of computers: 1st (1940–1956) vacuum tubes, machine language (e.g. ENIAC, UNIVAC-I); 2nd (1956–1963) transistors, assembly language, smaller/faster/less heat; 3rd (1964–1971) Integrated Circuits (ICs), high-level languages, OS introduced.

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Generations continued: 4th (1971–present) microprocessors (VLSI), personal computers, GUI; 5th (present & beyond) AI, ULSI, parallel processing, natural language, robotics.

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Classification by working principle: Analog (continuous physical quantities) vs Digital (discrete binary data) vs Hybrid (combination of both, e.g. hospital/ICU equipment). By size/capacity (fastest to smallest): Supercomputer > Mainframe > Minicomputer > Microcomputer/PC.

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Applications span business & banking, education & e-learning, healthcare & diagnostics, scientific research, defense & space, entertainment & media, and government & e-governance; limitations include no original intelligence/common sense, no feelings/emotions, and decision-making limited strictly to programmed logic.

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Primary storage is directly accessible by the CPU, volatile (RAM loses data on power-off), smaller capacity, higher cost per byte, very high access speed — e.g. RAM, ROM, Cache, Registers.

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Secondary storage is not directly accessible by the CPU (data is first brought into primary storage), non-volatile (retains data without power), larger capacity, lower cost per byte, slower access speed — e.g. Hard disk, Optical disk, Magnetic tape, Flash drive.

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Sequential access — data is read/written in order, one item after another (e.g. magnetic tape); slower for random lookups.

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Direct/Random access — any storage location can be accessed directly without reading through preceding items (e.g. hard disk, RAM); much faster for lookups.

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RAM (Random Access Memory) is volatile — read/write working memory; SRAM (fast, used for cache) and DRAM (cheaper, needs refreshing) are its two types.

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ROM (Read Only Memory) is non-volatile — permanently stores firmware/boot instructions, factory-written.

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PROM (Programmable ROM) — non-volatile; can be written only once by the user, using a special device.

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EPROM (Erasable PROM) — non-volatile; erased using ultraviolet (UV) light, then reprogrammed.

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EEPROM (Electrically Erasable PROM) — non-volatile; erased & rewritten electrically, byte-by-byte.

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Magnetic Tape — a sequential-access medium on a reel; cheap, high capacity; mainly used for backups/archiving.

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Magnetic Disk (Hard Disk) — direct-access medium made of rotating platters coated with magnetic material; the primary secondary-storage device of a computer.

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Cartridge Tape — a compact, self-contained magnetic tape cartridge, used for backup.

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Optical Disk / Compact Disk (CD/DVD) — data is read/written using a laser beam; CD (~700 MB), DVD (4.7 GB+); durable and portable.

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Zip Drive — a removable, higher-capacity floppy-like magnetic disk device (legacy technology, largely obsolete today); Flash Drive (USB / Pen Drive) — solid-state, non-volatile memory, no moving parts, compact and widely used for portable storage.

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Software is a collection of programs, procedures, and associated documentation that tells computer hardware what to do and how to do it.

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Hardware alone cannot perform any useful task; software is needed to control hardware, manage resources, and let users interact with the machine to solve real problems.

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System Software — Operating System (OS) manages hardware & resources and provides a platform for application software (e.g. Windows, Linux).

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System Software — Utility Programs support/maintain the system: antivirus, disk cleanup, backup, file compression tools.

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System Software — Programming Language Translators: compilers, interpreters, and assemblers that convert source code into machine-executable form.

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Application Software — general purpose & specific: word processors, spreadsheets, DBMS, presentation & graphics tools that perform user tasks.

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Machine Language (binary 0/1) — directly executed, fastest, no translator needed; but very hard to write/debug, hardware-dependent, error-prone.

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Assembly Language (mnemonics) — easier than machine code, efficient, close to hardware; but still hardware-dependent, needs an Assembler, harder than high-level languages.

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High-Level Language (English-like: C, Java, Python) — easy to write, read, debug, machine-independent/portable; but needs a Compiler/Interpreter, generally slower than machine/assembly code.

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Word Processing software creates, edits, and formats text documents (e.g. MS Word); Spreadsheet software organizes data in rows/columns and performs calculations with formulas (e.g. MS Excel).

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Presentation software creates slide shows for communicating information visually (e.g. MS PowerPoint); Graphics software creates and edits images/drawings (e.g. Photoshop, CorelDRAW).

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DBMS software creates, stores, and manages structured data/databases (e.g. Oracle, MySQL, MS Access).

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A computer network connects multiple computers to share data and resources.

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The OSI model has 7 layers (a conceptual reference model): 7. Application (network services directly to end-user apps: HTTP, FTP, SMTP), 6. Presentation (data translation, encryption, compression), 5. Session (establishes, manages, terminates sessions between hosts).

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OSI layers continued: 4. Transport (end-to-end delivery, reliability, flow control — TCP/UDP), 3. Network (logical addressing and routing of packets — IP), 2. Data Link (framing, physical/MAC addressing, error detection), 1. Physical (transmission of raw bits over the physical medium).

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The TCP/IP model condenses the OSI model's 7 layers into 4: Application (maps to OSI layers 5-7), Transport (maps to OSI layer 4), Internet (maps to OSI layer 3), and Network Access (maps to OSI layers 1-2).

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Hub (Physical layer) broadcasts incoming signal to all connected ports; has no intelligence.

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Bridge (Data Link layer) connects/segments two LANs, filtering traffic by MAC address; Switch (Data Link layer) intelligently forwards frames only to the destination port using a MAC address table.

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Router (Network layer) connects different networks and routes packets based on IP address.

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Guided (wired) media: Twisted-pair cable, Coaxial cable, Fiber-optic cable. Unguided (wireless) media: Radio waves, Microwaves, Infrared/satellite links.

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Protocols are rules that govern how data is formatted and transmitted (e.g. TCP, IP, UDP, HTTP, FTP, SMTP, DNS); Standards (e.g. IEEE 802.3, 802.11) ensure interoperability between vendors' equipment.

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Common network attacks: Virus/Worm/Malware, Denial of Service (DoS), Phishing, Man-in-the-middle, Spoofing.

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Cryptography secures data via encryption (plaintext → ciphertext) and decryption (ciphertext → plaintext); it may be symmetric (same key for encryption/decryption) or asymmetric (public/private key pair).

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A Firewall monitors and filters incoming/outgoing traffic based on defined security rules, acting as a barrier between a trusted internal network and an untrusted external network.

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Data communication is the exchange of data between two devices via a transmission medium.

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The basic communication process has five components: Sender, Message, Medium, Receiver, and Protocol (agreed rules).

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Data transmission speed is expressed in bps (bits per second) and baud rate (number of signal changes per second); bandwidth is the range of frequencies (or maximum data rate) a channel can carry.

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Simplex mode — data flows in one direction only (e.g. radio broadcast, keyboard to CPU).

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Half-Duplex mode — data flows both ways, but only one direction at a time (e.g. walkie-talkie).

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Full-Duplex mode — data flows both ways simultaneously (e.g. telephone conversation).

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A Modem = Modulator + Demodulator; converts digital signals from a computer into analog signals for transmission over telephone lines (modulation), and converts incoming analog signals back into digital form (demodulation); measured by baud rate and data transfer speed (bps); types include dial-up, DSL, and cable modems.

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Types of networks by coverage: PAN (a few meters, e.g. Bluetooth devices around one person) < LAN (a single building or campus) < MAN (a city or town) < WAN (country/continent-wide, e.g. the Internet).

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Bus topology — all nodes connected to a single central cable (backbone); drawback: entire network fails if the backbone cable breaks.

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Star topology — all nodes connected to a central hub/switch; drawback: central device failure brings down the whole network.

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Ring topology — each node connected to exactly two neighbors, forming a loop; drawback: a single broken link can disrupt the ring (unless dual ring).

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Mesh topology — every node connected to every other node; drawback: expensive, needs many cables/ports. Tree topology — hierarchical combination of star networks; depends heavily on the root/backbone.

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Computer protocols: TCP/IP (core suite governing reliable, routed delivery of data across networks), HTTP/HTTPS (transfer of web pages; HTTPS adds encryption/security), FTP (file transfer between computers), SMTP/POP3/IMAP (sending and retrieving email).

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Business data processing is the systematic use of computers to capture, process, store, and report business data such as payroll, billing, inventory, and accounts.

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Data storage hierarchy: Bit — smallest unit of data, a single binary digit (0 or 1); Byte — a group of (typically) 8 bits, represents one character.

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Data storage hierarchy continued: Field — a group of related characters/bytes (e.g. a 'Name' field); Record — a group of related fields (e.g. one student's complete record).

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Data storage hierarchy continued: File — a group of related records (e.g. all students' records); Database — a group of related files, organized for efficient access and management.

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Sequential organization — records stored and accessed one after another, in a particular order (e.g. by key/ID); simple but slow for direct lookup.

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Direct/Random organization — each record can be accessed directly using its address/key, without scanning other records.

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Indexed Sequential organization (ISAM) — records are stored sequentially but an index is maintained to allow both sequential and direct access.

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Master File — holds relatively permanent/reference data, updated periodically (e.g. employee master file); Transaction File — holds day-to-day transaction data used to update the master file (e.g. daily sales).

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Report File — holds data formatted for producing printed/displayed reports; Sort File — a temporary file created while sorting data into a required order.

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Backup File — a copy of a file kept for recovery in case the original is lost or damaged.

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File organization refers to the way records are physically arranged in a file, and follows the same three approaches as data organization: Sequential, Direct/Random, and Indexed Sequential.

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File utility programs help manage files — common operations include Copy, Delete, Rename, Move, Merge (combine two sorted files), Sort (arrange records in order), and Compress/Decompress (reduce/restore file size).