| Unit | Equals | Example |
|---|---|---|
| Bit (b) | 0 or 1 — smallest unit (BInary digiT) | One switch on/off |
| Nibble | 4 bits | One hex digit (0–F) |
| Byte (B) | 8 bits | One character 'A' = 01000001 |
| Kilobyte (KB) | 1,024 bytes (2¹⁰) — 1,000 in SI 'kB' | A short e-mail ≈ 2 KB |
| Megabyte (MB) | 1,024 KB | A photo 2–5 MB; an MP3 song 4 MB |
| Gigabyte (GB) | 1,024 MB | An HD movie 1–4 GB; phone RAM 8 GB |
| Terabyte (TB) | 1,024 GB | Laptop SSD 1 TB ≈ 250 movies |
| Petabyte (PB) | 1,024 TB | Google processes ~20 PB a day |
| Exabyte (EB) | 1,024 PB | All words ever spoken ≈ 5 EB |
| Zettabyte (ZB) | 1,024 EB | World data in 2025 ≈ 180 ZB |
| Yottabyte (YB) | 1,024 ZB | — (Ronnabyte & Quettabyte added in 2022) |
Number systems
| System | Base | Digits | Used for | Example of 25 |
|---|---|---|---|---|
| Binary | 2 | 0, 1 | Everything inside the computer | 11001 |
| Octal | 8 | 0–7 | Unix file permissions (chmod 755) | 31 |
| Decimal | 10 | 0–9 | Humans | 25 |
| Hexadecimal | 16 | 0–9, A–F | Colours (#FF0000), memory addresses, MAC addresses | 19 |
- IDecimal → binary: divide by 2, write remainders bottom-up. 25 → 12 r1, 6 r0, 3 r0, 1 r1, 0 r1 → 11001.
- IIBinary → decimal: multiply by powers of 2. 11001 = 16 + 8 + 0 + 0 + 1 = 25.
- IIIBinary → hex: group 4 bits. 1 1001 → 0001 1001 → 1 9 → 0x19. Hex → binary: each digit = 4 bits.
- IVASCII (1963): 7-bit, 128 characters — 'A' = 65, 'a' = 97, '0' = 48, space = 32. Unicode/UTF-8 covers 150,000+ characters including Devanagari (क = U+0915), emoji.
- V1 character = 1 byte (English), 3 bytes (Hindi in UTF-8). Signed 8-bit range −128…127; 32-bit int ≈ ±2.1 billion; 64-bit ≈ ±9.2 × 10¹⁸.
Speed and performance units
| Unit | Measures | Typical values |
|---|---|---|
| Hz / MHz / GHz | Clock cycles per second | Intel 4004: 740 kHz; Pentium: 60 MHz; today 3–6 GHz |
| MIPS | Million instructions per second | ENIAC 0.005; i486 54; modern CPU 500,000+ |
| FLOPS | Floating-point operations per second | Cray-1 160 MFLOPS; PS5 10 TFLOPS; RTX 5090 105 TFLOPS; El Capitan 1.7 EFLOPS |
| TOPS | Trillion AI operations per second | Copilot+ NPU 40–50 TOPS; iPhone 16 Neural Engine 35 TOPS |
| bps / Mbps / Gbps | Network speed (bits!) | 2G 50 kbps; 4G 100 Mbps; 5G 1–10 Gbps; fibre 1 Gbps |
| MB/s / GB/s | Storage throughput (bytes) | HDD 150 MB/s; SATA SSD 550 MB/s; PCIe 5 NVMe 14 GB/s |
| ms / µs / ns / ps | Time: 10⁻³ / 10⁻⁶ / 10⁻⁹ / 10⁻¹² s | Ping 20 ms; RAM 80 ns; one CPU cycle at 4 GHz = 0.25 ns |
| dpi / ppi | Dots / pixels per inch | Printer 300–1200 dpi; phone screen 460 ppi |
| Resolution | Pixels width × height | HD 1280×720; Full HD 1920×1080; 4K 3840×2160; 8K 7680×4320 |
| nm process | Transistor feature size | Pentium 800 nm → today 3 nm, 2 nm in 2025 |
// Keep exploring
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