Primary memory vs Secondary memory RAM vs ROM Static RAM vs Dynamic RAM PROM vs EPROM vs EEPROM Hard disk vs Floppy disk

1. Storage Devices
Ch. 4

2. Main Memory
I. Also known as Primary memory or
active memory or internal memory
II. Categorized as volatile and non
volatile memories, RAM is volatile
memory whereas ROM is non
volatile memory
III. Expensive
IV. Directly accessed by the CPU
V. Faster data access
VI. Temporary storage
VII. Connected computer through slots
VIII. Smaller or limited storage
capacity
Secondary memory
I. Also known as additional memory or
back memory or external memory
II. Always categorized as non volatile
memory
III. Cheaper
IV. Indirectly accessed by the CPU
V. Slower data access
VI. Permanent storage
VII. Connected computer through cables
VIII. Larger or extendible storage
capacity

3. RAM (Random Access Memory)
I. Volatile memory
II. Expensive
III. Faster data access
IV. Larger in size
V. Temporary storage
VI. Directly and easily access to
information stored in the RAM
VII. CPU can perform read or write
operations on RAM
VIII. Two types, SRAM and DRAM
ROM (Read Only Memory)
I. Non volatile memory
II. Cheaper
III. Slower data access
IV. Smaller in size
V. Permanent storage
VI. Indirectly and difficult access to
information stored in the ROM
VII. CPU can only perform read
operation on ROM
VIII. Three types, EROM, EPROM and
EEPROM

4. Static RAM
I. Data does not need to be refresh
periodically
II. Consume less power
III. Expensive
IV. Faster data access
V. Used in cache memory
VI. More reliable
Dynamic RAM
I. Data needs to be refreshed
periodically
II. Consume more power
III. Cheaper
IV. Slower data access
V. Used in main memory
VI. Less reliable

5. PROM
• One time
programmable
(OTP)
• No erase function
EPROM
• Reprogrammable
• Erased with UV
light
EEPROM
• Reprogrammable
• Erased electrically

6. Hard disk
I. Expensive
II. Modern technology
III. Large storage capacity
(Increases day by day)
IV. Faster data accessing and
transferring rate
V. Larger in size
VI. Heavyweight
VII. Fixed in System unit
VIII. Difficultly transportable
IX. More reliable
X. More Noisy
Floppy disk
I. Very cheap
II. Older technology
III. Very small storage capacity
IV. Slower data accessing and
transferring rate
V. Smaller In size
VI. Lightweight
VII. Not fixed / portable
VIII. Easily transportable
IX. Less reliable
X. Very less noisy