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UGC NET PAPER 1 · UNIT 08 · MODULE 2: DEVICES, MEMORY AND OPERATING SYSTEMS · TOPIC 5

Memory and Storage

The memory hierarchy from register to tape, RAM versus ROM, cache, secondary and optical storage, and the comparison tables examiners reuse.

  • 4 sub-topics
  • 2 min read
  • Topic 5 of 18

What this topic covers

4 sub-topics, in the order to study them. Tap one to jump to it.

  1. 5.1Memory HierarchyFrom fastest, smallest and most expensive to slowest, largest and cheapest: Registers → Cache → RAM (main memory) → Secondary storage (SSD or HDD) → Tertiary and offline…
  2. 5.2Primary MemoryRAM (Random Access Memory): volatile (data lost when power is off), read and write, holds currently running programs and data.
    • RAM (Random Access Memory)
    • SRAM (Static RAM)
    • cache
    • DRAM (Dynamic RAM)
    • ROM (Read Only Memory)
  3. 5.3Secondary StorageCovers Magnetic, Optical, Solid-state, Cloud storage.
    • Magnetic
    • Optical
    • Solid-state
    • SSD
    • Cloud storage
  4. 5.4Key DifferencesRAM ROM Volatile Non-volatile Read and write Mostly read-only Temporary working space Permanent start-up instructions Primary memory Secondary memory Directly accessed by…
    • Quick traps

Revision mode hides the full explanations and keeps each section's key terms, lists and tables and the Memory Capsule. Use it from your second read onward.

5.1Memory Hierarchy#

In brief

From fastest, smallest and most expensive to slowest, largest and cheapest: Registers → Cache → RAM (main memory) → Secondary storage (SSD or HDD) → Tertiary and offline…

From fastest, smallest and most expensive to slowest, largest and cheapest: Registers → Cache → RAM (main memory) → Secondary storage (SSD or HDD) → Tertiary and offline (optical, tape). The principle is a trade-off of speed, cost and capacity.

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5.2Primary Memory#

In brief

RAM (Random Access Memory): volatile (data lost when power is off), read and write, holds currently running programs and data.

  • RAM (Random Access Memory)
  • SRAM (Static RAM)
  • cache
  • DRAM (Dynamic RAM)
  • ROM (Read Only Memory)
  • PROM
  • EPROM
  • EEPROM

RAM (Random Access Memory): volatile (data lost when power is off), read and write, holds currently running programs and data.

  • SRAM (Static RAM): faster, costlier, used in cache, no refreshing.

  • DRAM (Dynamic RAM): slower, cheaper, needs constant refreshing, used as main memory.

ROM (Read Only Memory): non-volatile, holds start-up instructions (BIOS or firmware). Types: PROM (programmable once), EPROM (erased with UV light), EEPROM (erased electrically) and Flash memory (block-erase, used in pen drives and SSD).

Cache memory: a small, very fast memory between CPU and RAM that holds frequently used data. Levels L1 (inside CPU, fastest), L2 and L3. Virtual memory: use of disk space to extend RAM.

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5.3Secondary Storage#

In brief

Covers Magnetic, Optical, Solid-state, Cloud storage.

  • Magnetic
  • Optical
  • Solid-state
  • SSD
  • Cloud storage
  • Access methods

  • Magnetic: hard disk (HDD), floppy, magnetic tape (sequential access, used for backup and archives).

  • Optical: CD (about 700 MB), DVD (about 4.7 GB), Blu-ray (about 25 GB per layer).

  • Solid-state: SSD, pen drive, memory card. No moving parts, faster and more durable than HDD.

  • Cloud storage: Google Drive, OneDrive, Dropbox.

Access methods: sequential (tape), direct or random (disk, RAM).

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5.4Key Differences#

In brief

RAM ROM Volatile Non-volatile Read and write Mostly read-only Temporary working space Permanent start-up instructions Primary memory Secondary memory Directly accessed by…

  • Quick traps
RAM ROM
Volatile Non-volatile
Read and write Mostly read-only
Temporary working space Permanent start-up instructions
Primary memory Secondary memory
Directly accessed by CPU Not directly accessed
Fast, costly, small Slow, cheap, large
Volatile (RAM) Non-volatile

Quick traps: Cache is faster than RAM. Registers are the fastest of all. ROM is non-volatile. An SSD has no moving parts.

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Test yourself on Memory and Storage

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↑ Module 2: Devices, Memory and Operating Systems · All 18 topics in ICT · Unit overview and sample MCQs

Last updated: . Notes are a revision aid; check official UGC sources for any rule or scheme that changes over time. Spotted a mistake? Write to netlawverse@gmail.com.