Memory and Storage devices
Category |
Devices |
Primary Memory |
RAM, ROM, Cache Memory |
Internal Secondary Storage |
Hard Disk Drive (HDD), Solid State Drive (SSD) |
External Secondary Storage |
DVD/CD, DVD-RAM, Blu-ray Disc, USB Memory Stick/Flash Memory, Removable Hard Drive |
Comparison of RAM and ROM
Feature |
RAM |
ROM |
Type of Memory |
Temporary memory |
Permanent memory |
Volatility |
Volatile (contents lost when powered off) |
Non-volatile (contents retained) |
Read/Write |
Can be written to and read from |
Data stored cannot be altered |
Usage |
Stores data, files, part of an application or OS |
Always used to store BIOS and other data |
Virtual Memory vs. Normal Memory Management
Feature |
Virtual Memory |
Normal Memory Management |
RAM Utilization |
Programs larger than physical memory can be executed |
Limited by the available physical memory |
Data Movement |
Data moved in and out of HDD/SSD as needed |
No movement of data between memory and storage |
Disk Thrashing |
Can lead to disk thrashing if not managed properly |
No disk thrashing as data stays in RAM |
DRAM(Dynamic RAM)
Aspect |
Description |
Composition |
Consists of transistors and capacitors |
Operation |
Capacitor holds bits of information (0 or 1); transistor acts as a switch for reading/writing |
Refresh |
Requires constant refreshing (every 15 microseconds) to prevent data loss |
Magnetic Storage (Hard Disk Drives - HDD)
Aspect |
Description |
Data Storage |
Data is stored in a digital format on the magnetic surfaces of disks (platters) with read-write heads |
Latency |
Slower data access compared to RAM; latency occurs as the read-write heads search for the correct data |
Fragmentation |
Fragmentation occurs over time, affecting performance; defragmentation software can improve this |
Memory Sticks/Flash Memory
Uses solid-state technology; small, lightweight devices suitable for transferring files between computers |
Virtual Memory
Aspect |
Description |
Purpose |
Extends physical RAM, allowing larger programs to run; utilizes hard disk or SSD as swap space |
Paging |
Uses paging to store and retrieve data from HDD/SSD, copying it into RAM |
Advantages |
- Programs can be larger than physical memory
- Reduces the need for expensive RAM |
Blu-ray Discs vs DVDs
Aspect |
Blu-ray |
DVDs |
Laser Color |
Blue |
Red |
Wavelength of Laser Light |
405 nm |
650 nm |
Storage Capacity (Dual-Layer) |
Up to 50 GB |
8.5 GB (for dual-layer DVDs) |
Interactivity |
Greater interactivity; high definition movies |
Limited interactivity; standard definition movies |
Data Transfer Rate |
36 Mbps |
10 Mbps |
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Primary and Secondary Storage
Storage Type |
Storage Type |
Primary Memory |
Directly addressable by CPU, contains RAM, ROM, and cache memory |
Secondary Storage |
Not directly addressable by CPU, non-volatile devices (e.g., HDD, SSD, DVD) |
Comparison of DRAM and SRAM
Feature |
DRAM |
SRAM |
Construction |
Transistors and capacitors |
Flip flops |
Refresh Requirement |
Needs constant refreshing |
No constant refreshing |
Cost |
Less expensive |
More expensive |
Power Consumtion |
Consumes less power |
Consumes more power |
Memory Capacity |
Higher memory capacity |
Lower memory capacity |
Types of Optical Storage Media
Media Type |
Characteristics |
CD/DVD |
Uses laser light to read and write data on metal alloy or organic dye layer |
Blu-ray |
Uses blue laser light, smaller pits and lands, higher capacity, and dual-layering |
Cloud Storage Benefits and Drawbacks
Aspect |
Benefits |
Drawbacks |
Data Redundancy |
Increased data redundancy and accessibility |
Security concerns and potential data loss |
Accessibility |
Access data from anywhere with an internet connection |
Relinquishing control over data security |
Cost |
Cost-effective storage solutions |
Risk of data loss from hacking and security breaches |
SRAM(Static RAM)
Aspect |
Description |
Composition |
Uses flip-flops to hold each bit of memory |
Refresh |
No constant refreshing needed |
Speed |
Faster data access compared to DRAM (typically, access time for SRAM is 25 ns) |
SSD(Solid State Drive)
Aspect |
Description |
Composition |
Uses NAND or NOR chips to control the movement of electrons, storing data as 0s and 1s in transistors |
Advantages |
- More reliable (no moving parts)
- Lighter and suitable for laptops
- Faster data access than HDD |
Virtual Memory
Aspect |
Description |
Purpose |
Extends physical RAM, allowing larger programs to run; utilizes hard disk or SSD as swap space |
Paging |
Uses paging to store and retrieve data from HDD/SSD, copying it into RAM |
Advantages |
- Programs can be larger than physical memory
- Reduces the need for expensive RAM |
Cloud Storage
Aspect |
Description |
Types |
-Public cloud (different provider and client companies)
-Private cloud (integrated client and provider)
-Hybrid cloud (combination of public and private) |
Reduncy |
Data redundancy on multiple servers to ensure availability |
Security Risks |
Risks include physical security, natural disasters, and potential data loss from hacking or other breaches |
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