Lecture on Computer Memory and Storage

The Role of Memory in Computers

• Memory helps computers perform functions similar to human memory: storing information, learning, and planning.
• All data in computers, from movies to text files, are stored as bits (binary digits).
• Bits are stored in memory cells that can switch between two states (0 and 1).
• Files and programs consist of millions of bits.
• CPU processes these bits, acting as the computer's brain.

Types of Computer Memory

• Short-term Memory: Used for immediate tasks.
• Long-term Memory: Used for permanent storage.

Random Access Memory (RAM)

• Dynamic RAM (DRAM)
  • Each cell has a transistor and a capacitor.
  • Stores electrical charges: 0 (no charge) or 1 (charged).
  • Dynamic because it requires periodic recharging.
  • Low latency (~100 nanoseconds).
• Static RAM (SRAM)
  • Made of six interlocked transistors.
  • Does not need refreshing.
  • Fastest memory but expensive and space-consuming.

Long-term Storage Devices

• RAM and cache only retain data while powered.
• Three major types of long-term storage:

1. Magnetic Storage

• Data stored as magnetic patterns on a spinning disk.
• Cheapest form of storage.
• High latency compared to DRAM.

2. Optical Storage

• Uses disks with reflective coatings (e.g., DVD, Blu-ray).
• Bits encoded as light and dark spots.
• Slow latency and lower capacity.

3. Solid-state Drives (SSDs)

• No moving parts.
• Use floating gate transistors.
• Fast but prone to wear out with repeated writes.

Durability and Future of Memory

• Computer memory often degrades quickly.
• Environmental heat can demagnetize hard drives and degrade optical media.
• Charge leakage is an issue for floating gates in SSDs.
• Current storage media have a lifespan of less than 10 years.
• Scientists are exploring materials at the quantum level for faster, smaller, and more durable memory solutions.

Conclusion

• Both human and computer memory are temporary in nature.
• Advances continue to be made in the pursuit of more durable memory solutions.