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Data Storage and Measurement

Aug 31, 2025

Overview

This lecture explains how data capacity is measured in computers, focusing on binary representation, units of measurement, and conversion methods relevant for exams.

Binary Storage Basics

  • All computer data is stored in binary (bits: 0s and 1s), representing two states.
  • Physical devices use different methods (e.g., charge/no charge, magnetic poles) to store bits.
  • A bit (binary digit) stores the simplest data, such as true/false or on/off.

Units of Data Measurement

  • Four bits make a nibble; eight bits make a byte.
  • A byte can represent numbers, letters, symbols, or parts of other data types (images/sounds).
  • Larger units: kilobyte (KB), megabyte (MB), gigabyte (GB), terabyte (TB), petabyte (PB).

Binary vs Decimal Measurements

  • Binary measurement: 1 KB = 1024 bytes, 1 MB = 1024 KB, etc.
  • Decimal approximation: 1 KB ≈ 1000 bytes, 1 MB ≈ 1,000,000 bytes, etc.
  • For exams, decimal approximations are acceptable and commonly used by storage manufacturers.

Converting Between Units

  • Sequence: kilo (thousand), mega (million), giga (billion), tera (trillion), peta (quadrillion).
  • To convert up a unit, divide by 1000; to convert down, multiply by 1000.
  • To convert from bytes to bits, multiply by 8 (since 1 byte = 8 bits).

Practical Examples

  • 1470 KB = 1.47 MB (divide by 1000).
  • 740 KB = 0.74 MB (divide by 1000).
  • 25 KB = 25,000 bytes (multiply by 1000); in bits: 25,000 × 8 = 200,000 bits.

Symbols and Capitalization

  • KB, MB, GB, TB, PB: capital B means bytes.
  • Network speeds use a lowercase 'b' for bits per second (e.g., Mbps).
  • 1 MB (megabyte) is 8 times larger than 1 Mb (megabit).

Key Terms & Definitions

  • Bit — smallest unit of data, 0 or 1.
  • Byte — 8 bits.
  • Nibble — 4 bits.
  • Kilobyte (KB) — ≈ 1000 or 1024 bytes.
  • Megabyte (MB) — ≈ 1,000,000 or 1,048,576 bytes.
  • Gigabyte (GB) — ≈ 1,000,000,000 bytes.
  • Terabyte (TB) — ≈ 1,000,000,000,000 bytes.
  • Petabyte (PB) — ≈ 1,000,000,000,000,000 bytes.
  • Mb — megabit (bits, not bytes).

Action Items / Next Steps

  • Memorize the order: kilo, mega, giga, tera, peta.
  • Practice converting between units (bytes, KB, MB, GB, TB).
  • Remember to multiply/divide by 8 when converting between bytes and bits.

Full transcript