Computer And Their Components (Copy)
Cheat Sheet: A Level Computer Science – Hardware, Memory, Storage & Embedded Systems
1. Need for Input, Output, Primary Memory & Secondary Storage
| Component | Purpose |
|---|---|
| Input Devices | Send data to the system (e.g., keyboard, microphone) |
| Output Devices | Display or present data from the system (e.g., monitor, speakers) |
| Primary Memory (RAM, ROM) | Temporarily or permanently store data needed by the CPU |
| Secondary Storage | Long-term data storage (e.g., HDD, SSD) |
| Removable Storage | Portable storage (e.g., USB drives, memory cards, optical discs) |
2. Embedded Systems
- Definition: A computer system built into a larger device to perform a specific function
- Examples: Washing machines, ATMs, traffic lights, microwave ovens
| Benefits | Drawbacks |
|---|---|
| Low cost, small size | Hard to upgrade or reprogram |
| Efficient for dedicated tasks | Limited functionality |
| Low power consumption | Maintenance can be difficult |
3. Principal Hardware Operations
| Device | Operation |
|---|---|
| Laser Printer | Electrostatic charge attracts toner to paper, fixed using heat |
| 3D Printer | Adds material layer by layer using plastic or resin |
| Microphone | Converts sound waves into electrical signals |
| Speakers | Convert digital audio signals into sound waves |
| Magnetic Hard Disk | Uses spinning platters and read/write heads to store data magnetically |
| Solid-State (Flash) Memory | No moving parts, uses electronic circuits for data storage |
| Optical Disc Reader/Writer | Uses lasers to read/write data on discs (e.g., CDs, DVDs) |
| Touchscreen | Detects touch input (capacitive or resistive technologies) |
| Virtual Reality Headset | Combines display and motion tracking for immersive experiences |
4. Buffers
- Definition: Temporary memory storage used to compensate for differences in data processing speeds
- Use: Ensures smooth data transfer (e.g., print spooling, streaming video/audio)
5. RAM vs ROM
| Feature | RAM (Random Access Memory) | ROM (Read-Only Memory) |
|---|---|---|
| Volatility | Volatile (data lost when off) | Non-volatile |
| Writable | Read/write | Read-only (or limited write variants) |
| Use | Temporary storage during execution | Permanent storage for firmware |
| Example | Programs currently in use | BIOS or bootloader |
6. SRAM vs DRAM
| Feature | Static RAM (SRAM) | Dynamic RAM (DRAM) |
|---|---|---|
| Speed | Faster | Slower |
| Cost | More expensive | Cheaper |
| Size | More space per bit | Compact |
| Refreshing | No need to refresh | Needs constant refreshing |
| Use | CPU cache, registers | Main memory (system RAM) |
7. PROM, EPROM, EEPROM
| Type | Features | Use |
|---|---|---|
| PROM | Can be programmed once only | Firmware |
| EPROM | Erasable using UV light, then reprogrammable | Development, legacy systems |
| EEPROM | Erased electrically, byte-level write | BIOS, modern firmware |
8. Monitoring and Control Systems
Monitoring System
- Function: Continuously collects data using sensors
- No automatic response
- Examples: Weather stations, patient monitors
Control System
- Function: Uses sensor data to automatically adjust actuators
- Examples: Air conditioning, autopilot
Sensors
| Sensor | Purpose |
|---|---|
| Temperature | Detects heat (e.g., thermostats) |
| Pressure | Measures force or weight (e.g., barometers) |
| Infra-red | Detects motion or proximity |
| Sound | Detects audio input or volume levels |
Actuators
- Convert electrical signals into physical action (e.g., motors, valves)
Feedback
- Sensor readings are sent back to the system to decide future actions
- Enables dynamic, automated responses in control systems