Computers & Mobile Devices – Comprehensive Exam Notes

Definition: computer dedicated to providing one or more services to other computers on a network.
Physical styles:
- Rack server: slides into a 19-inch rack.
- Blade server: ultra-slim module that shares backplane power/network.
- Tower server: upright cabinet resembling a desktop tower.
Dedicated-server roles (Table 3-1); examples:
- Application, backup, database, DNS, file, FTP, game, home, list, mail, network, print, web.
Virtualization
- Software layer lets one physical machine emulate multiple virtual servers to consolidate workloads and increase utilization.
- Financial & environmental impact: fewer physical boxes $\Rightarrow$ reduced power, cooling, and floor-space costs.
Server farm: multiple servers networked in a single location; typical for cloud and enterprise data centers.
Mainframe: large, costly server able to power hundreds or thousands of concurrent users and high-volume transactions.

Terminal = computer with limited processing, relying on a host for heavy lifting.
- Thin client: terminal that looks like desktop but has minimal local resources.
Retail/transactional specializations:
- POS (Point-of-Sale) terminal: records purchases, processes cards, updates inventory.
- Modern variant: self-service checkout kiosks (Figure 3-10) let customers scan/pay themselves.
- ATM: self-service banking terminal connected via network to bank host (Figure 3-11).
- Self-service kiosks (Table 3-2):
- Financial, photo, ticket, vending, visitor management, etc.

Fastest, most powerful, most expensive systems.
Performance: many trillions of instructions per second; modern examples surpass $1\;\text{peta-FLOPS} = 10^{15}$ floating-point ops/s.
Deployed for climate modeling, cryptography, nuclear simulations, and large-scale scientific research.

Environment delivering shared resources/services via the Internet.
Users access storage, applications, or processing remotely; underlying hardware may be server farms and virtualized resources.
Advantages: scalability, pay-as-you-go, device agnosticism, reduced local maintenance.

Smartphone
- Internet-capable phone bundling tools: calendar, contacts, calculator, notepad, games, browser, and app ecosystem.
- Input: multi-touch screens; some models still include slide-out or front-face mini keyboards for tactile entry.
E-Book Reader
- Purpose-built for reading digital publications; uses e-ink/e-paper for low power and glare-free viewing.
- Supports on-device editing/annotation and remote print ordering (Figure 3-21).
Wearable Devices
- Designed to be worn—e.g., activity trackers, smartwatches, smart glasses (Figure 3-22).
- Enable ambient data collection (steps, heart rate), quick notifications, AR overlays, hands-free interaction.

Game console
- Dedicated home/portable machine for single or multiplayer gaming.
Handheld game device
- Self-contained unit with integrated screen, speakers, controls.
Controllers
- Gamepads, joysticks, racing wheels, dance pads, motion-sensing systems (Figure 3-23); each offers different ergonomic and immersion advantages.

Special-purpose computer functioning as one component inside a larger product.
- Domains: consumer electronics (TVs, microwaves), home automation (thermostats, alarms), automobiles (engine control, safety), industrial robots, office machines (printers).
Characteristics: miniature size, real-time constraints, firmware-centric, usually invisible to end user.

Personal computers (desktop): fits on desk, $1$ user, $\$\$ several hundred → several thousand$ .
Mobile computers/devices: lap/hand size, $1$ user, <\$100 to $\$\$ several thousand$ .
Game consoles: small box, $1–\text{several}$ users, up to $\$\$ hundreds$ .
Servers: small cabinet to room, $2–1000+$ users, $\$\$ hundreds → millions$ .
Supercomputers: full room, $100–1000+$ users, $\$0.5\,\text{million} – \$\$ billions$ .
Embedded: miniature, embedded cost folded into product price.

Biometric protection: fingerprint readers integrated into many mobile devices (Figure 3-27) for identity verification.
Failure factors
- Aging components.
- Electrical anomalies: undervoltage (brownout) or overvoltage/power surge.
Defensive hardware
- Surge protector (surge suppressor): uses circuitry to maintain a stable current, blocking high-voltage spikes (Figure 3-28).
- UPS (Uninterruptible Power Supply)
- Combines surge protection with battery backup; supplies electricity during outages (Figure 3-29).
- Buffer time lets users save work and shut down gracefully, protecting data integrity.

RSI (Repetitive Strain Injury): damage to muscles/tendons/nerves from repeated motions (e.g., typing).
CVS (Computer Vision Syndrome): eye strain, dryness, blurred vision after prolonged screen exposure.
Ergonomics: science of designing workplace tools/layouts for comfort, efficiency, safety.
- Adjustable chairs, monitor height, and keyboard trays help align with varied body builds (Figure 3-32).
Technology addiction: overuse to the point that digital activities crowd out face-to-face interactions, exercise, and rest.

Memorize the definitions and distinguishing features of each device class (laptop vs. tablet vs. handheld, etc.).
Understand dedicated-server types and how virtualization splits one physical server into many logical servers.
Recall protective hardware (surge protector, UPS) and the electrical hazards they mitigate.
Be able to cite at least three examples of embedded systems in cars or homes.
Connect ergonomic principles to prevention of RSI and CVS; recognize signs of technology addiction.
Translate large performance/value numbers into scientific notation (e.g., quadrillion $=10^{15}$ ) for quick comparisons.