💻 Computer Basics
Hardware, software, generations, memory and storage units.
💡 What is a Computer?
A computer is an electronic device that takes input, processes it, stores data, and gives output. It works on the IPO cycle: Input → Process → Output.
Hardware — physical parts you can touch: CPU, RAM, hard disk, keyboard, monitor.
Software — programs and instructions: Windows, MS Word, Chrome browser.
Types of memory:
• RAM (Random Access Memory) — temporary, volatile. Loses data when power off. Fast.
• ROM (Read Only Memory) — permanent, non-volatile. Stores BIOS/firmware.
• Cache — fastest memory, inside CPU. Stores frequently used data.
• Hard Disk / SSD — permanent storage. HDD uses magnetic disks; SSD uses flash chips (faster).
CPU (Central Processing Unit) — the brain. Contains ALU (arithmetic/logic), CU (control unit), registers. Speed measured in GHz.
1st Gen (1940s-50s) — Vacuum tubes. ENIAC. Very large, high power, low reliability.
2nd Gen (1950s-60s) — Transistors. Smaller, faster, cheaper. Assembly language.
3rd Gen (1960s-70s) — Integrated Circuits (ICs). High-level languages (FORTRAN, COBOL).
4th Gen (1970s-present) — Microprocessors. Intel 4004 (1971). Personal computers.
5th Gen (present-future) — AI, parallel processing, natural language. Still evolving.
1 Bit = smallest unit (0 or 1)
1 Byte = 8 bits | 1 KB = 1024 Bytes | 1 MB = 1024 KB | 1 GB = 1024 MB | 1 TB = 1024 GB | 1 PB = 1024 TB
Input devices: Keyboard, Mouse, Scanner, Microphone, Webcam, Joystick, Light Pen, OMR, OCR, MICR, Barcode Reader
Output devices: Monitor (VDU), Printer, Speaker, Projector, Plotter
Both I/O: Touchscreen, Modem, USB drive
Computer Architecture — IPO Cycle
AnimationEvery computer operation — from typing a letter to rendering a game — goes through this same cycle.
Computer Concepts Explorer
Interactive• Temporary / Volatile — data lost when power is off
• Read and Write both possible
• Used as working memory — stores currently running programs and data
• Faster than storage but slower than cache
• Types: DRAM (Dynamic RAM — needs refresh), SRAM (Static RAM — faster, in cache)
• Size: typically 4GB to 64GB in modern computers
ROM (Read Only Memory):
• Permanent / Non-volatile — data preserved even without power
• Generally Read Only (some modern types can be rewritten)
• Stores firmware — BIOS (Basic Input Output System)
• Slower than RAM
• Types: PROM (Programmable ROM), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM — Flash memory used in USB drives, SSDs)
Key distinction: RAM = workspace (like a desk). ROM = instruction manual (like a book). Storage (HDD/SSD) = filing cabinet.
Exam tip: Flash memory (pen drives, SSDs) is a type of EEPROM — non-volatile but can be rewritten electrically.
1 Bit = 0 or 1 (smallest unit)
1 Nibble = 4 bits
1 Byte = 8 bits
1 KB (Kilobyte) = 1024 Bytes = 2^10 Bytes
1 MB (Megabyte) = 1024 KB = 2^20 Bytes
1 GB (Gigabyte) = 1024 MB = 2^30 Bytes
1 TB (Terabyte) = 1024 GB = 2^40 Bytes
Therefore: 1 TB = 1024 GB = 1024 × 1024 MB = 1,048,576 MB
A nibble = 4 bits (half a byte). Rarely used in practice but appears in exams.
Why 1024 and not 1000? Computers work in binary (powers of 2). 2^10 = 1024 ≈ 1000. So computer manufacturers use 1024-based units internally, while storage device makers sometimes advertise using 1000 (decimal) — which is why a "1TB" hard drive shows as ~931 GB in Windows.
Mnemonic: Big Kings Might Give Tasty Pudding = Bit, KB, MB, GB, TB, PB