Primary Memory (Main Memory)

Characteristics:

• Volatile memory (data is lost when power is turned off).
• Directly accessible by the CPU.
• Faster than secondary memory.
• Includes RAM and cache memory.

a. Random Access Memory (RAM)

• Description: Temporary storage that holds data and instructions currently being used by the CPU.
• Types:
  • DRAM (Dynamic RAM): Requires periodic refreshing to maintain data. Commonly used as main memory.
  • SRAM (Static RAM): Faster and more expensive than DRAM, does not need to be refreshed. Used for cache memory.
• Characteristics:
  • High-speed access.
  • Volatile.
  • Used for temporary storage while the computer is running.

b. Cache Memory

• Description: A small, high-speed memory located close to the CPU to store frequently accessed data and instructions.
• Levels:
  • L1 Cache: Smallest and fastest, located inside the CPU.
  • L2 Cache: Larger than L1, slightly slower, located on the CPU or a separate chip.
  • L3 Cache: Larger than L2, shared among cores, located on the CPU.
• Characteristics:
  • Extremely fast access.
  • Volatile.
  • Reduces latency in data access.

2. Secondary Memory (Storage)

Characteristics:

• Non-volatile memory (data is retained even when power is off).
• Slower than primary memory.
• Used for long-term data storage.
• Includes hard drives, SSDs, optical discs, and USB drives.

a. Hard Disk Drive (HDD)

• Description: Traditional storage device that uses spinning magnetic disks to read/write data.
• Characteristics:
  • Large storage capacity.
  • Slower access speed compared to SSDs.
  • Mechanical components (susceptible to physical damage).

b. Solid State Drive (SSD)

• Description: Modern storage device that uses flash memory to store data.
• Characteristics:
  • Faster access speed than HDDs.
  • No moving parts (more durable and reliable).
  • Higher cost per gigabyte than HDDs.

c. Optical Disc

• Description: Storage media that uses laser technology to read/write data (e.g., CDs, DVDs, Blu-ray discs).
• Characteristics:
  • Portable and removable.
  • Lower storage capacity compared to HDDs and SSDs.
  • Slower access speed.

d. USB Flash Drive

• Description: Portable storage device that uses flash memory.
• Characteristics:
  • Portable and removable.
  • Faster access speed than optical discs.
  • Lower storage capacity compared to HDDs and SSDs.

3. Tertiary Memory

Characteristics:

• Non-volatile memory.
• Used for large-scale, long-term data storage and backup.
• Includes tape drives and cloud storage.

a. Magnetic Tape

• Description: Storage medium used primarily for data backup and archival.
• Characteristics:
  • Very high storage capacity.
  • Slow access speed (sequential access).
  • Cost-effective for large-scale storage.

b. Cloud Storage

• Description: Online storage service that allows users to store and access data over the internet.
• Characteristics:
  • Accessible from anywhere with an internet connection.
  • Scalable storage capacity.
  • Dependence on internet connectivity and service providers.