💻 Computer Fundamentals

1.1What is a computer?

Definition

A computer is an electronic machine that accepts data as input, processes it according to a set of stored instructions, and produces output — and does all of this very, very fast.

History — quick tour

• Abacus (~2500 BC): the original calculator. Beads on rods. Still kind of works.
• Charles Babbage (1830s): designed the Analytical Engine. Never finished it, but he's called the "Father of Computer."
• ENIAC (1945): first general-purpose electronic computer. Filled an entire room. Weighed 30 tons.
• Today: your phone is a million times more powerful and fits in your pocket.

Generations of computers

Characteristics

• Speed — billions of operations per second.
• Accuracy — never makes a math mistake (if you programmed it right).
• Storage — remembers gigabytes of data, forever if you want.
• Diligence — doesn't get tired, bored, or hungry.
• Versatility — same machine writes essays, plays games, and does accounts.
• Automation — once started, can run without you watching.

Types of computers

• By size: Supercomputer → Mainframe → Mini → Micro (PC, laptop, phone).
• By purpose: General-purpose (your laptop) vs Special-purpose (ATM, traffic signal).
• By data handled: Analog (measures continuous things — speedometer), Digital (counts in 0s and 1s — laptop), Hybrid (both — hospital patient monitor).

Applications

• Education — online classes, simulations, e-books.
• Banking — ATMs, online banking, eSewa, Khalti.
• Government — Nagarik App, IRD, passport issuance.
• Healthcare — patient records, MRI/CT imaging.
• Entertainment — YouTube, games, reels.

1.2Overview of a computer system

1.2.1 Data and data processing

Data = raw, unorganized facts (numbers, names, dates). Information = data after it's been processed into something useful. Data processing is the conversion: Input → Process → Output.

1.2.2 Hardware

Hardware is every physical part of a computer — anything you can touch. It has three jobs: take input, process it, give output (plus store stuff).

Input Unit

Devices that send data into the computer.

• Keyboard, mouse, touchscreen, microphone, webcam, scanner, barcode reader.

CPU — Central Processing Unit

The "brain." It has three sub-parts:

• CU (Control Unit) — traffic police; tells other parts what to do and when.
• ALU (Arithmetic Logic Unit) — the calculator; does all math and comparisons.
• Registers — tiny super-fast memory inside the CPU itself.

Output Unit

Devices that show you the result.

• Monitor, printer, speaker, projector, headphones.

Storage devices

Memory is split into two big families:

• Primary memory (also called main memory) — RAM & ROM. Fast, small, directly connected to the CPU.
• Auxiliary memory (also called secondary) — HDD, SSD, pen drive, CD/DVD, memory card. Slower, bigger, keeps data even when power is off.

RAM vs ROM

• RAM (Random Access Memory) — read + write, volatile. Holds whatever's running right now.
• ROM (Read Only Memory) — read-only, non-volatile. Stores startup instructions (BIOS).

Cache memory

A tiny, ultra-fast memory sitting between CPU and RAM. Stores the things the CPU uses most often.

1.2.3 Software

Software = a set of instructions (programs) that tell hardware what to do. Hardware without software is a paperweight.

Types of software

• System software — runs the computer itself.
  • Operating System (Windows, Linux, macOS, Android).
  • Device drivers (so the printer/camera/etc. actually works).
  • Utilities (antivirus, backup, disk cleanup).
• Application software — what YOU use to get work done.
  • MS Word, Excel, Chrome, VLC, Photoshop, WhatsApp.
• Utility software — sometimes listed separately; small tools: zip, antivirus, defragmenter.

Programming language & its types

A programming language is the language humans use to write instructions for a computer.

• Low-level languages
  • Machine language — pure 0s and 1s. What the CPU actually runs. Impossible for humans to write comfortably.
  • Assembly language — uses short codes like MOV, ADD. Needs an assembler to convert to machine code.
• High-level languages — closer to English. Need a compiler or interpreter.
  • Examples: C, C++, Java, Python, JavaScript.
• Translators:
  • Compiler — translates the whole program once (C, C++).
  • Interpreter — translates line by line (Python).
  • Assembler — converts assembly → machine code.

1.3Concept of Multimedia

Multimedia = combining multiple media forms — text, graphics, audio, video, animation — in one computer program.

Elements of multimedia

• Text — the foundation.
• Graphics/Images — JPG, PNG, GIF.
• Audio — MP3, WAV.
• Video — MP4, AVI.
• Animation — GIF, Flash-era, modern CSS/JS.

Uses

• Education (e-learning, simulations).
• Entertainment (films, games, reels).
• Advertising (flashy billboards that loop a video).
• Training (virtual labs, flight simulators).

1.4File Management

1.4.1 Physical structure of the disk

A hard disk is made of stacked circular plates (platters) with magnetic surfaces. Data is stored on concentric circles called tracks, each split into sectors. Same-position tracks across all platters together form a cylinder. A moving arm with a read/write head reads the magnetic bits.

SSDs (solid-state drives) have no moving parts — they store data in flash chips instead of spinning platters. Much faster, no seek time.

1.4.2 File and folder

• File — a named collection of related data stored on a disk. Every file has a name and an extension (resume.pdf, photo.jpg).
• Folder (directory) — a container that holds files and other folders. Helps you stay organized.

1.4.3 Types of files and file extensions

Tip: the part after the last dot in a filename is the extension. It tells Windows/Linux which app should open it.