1. What is Computer Memory?
Computer memory is a physical device used to store data, instructions, and results temporarily or permanently.
It allows the computer to process information quickly and efficiently.
Why Memory is Required?
- To store program instructions
- To store input data
- To store intermediate results
- To store final output
Without memory, a computer cannot function.
?? 2. Memory Organization & Hierarchy
Computer memory is organized in a hierarchical manner based on:
- Speed
- Cost
- Storage capacity
Memory Hierarchy Order:
- Register Memory (Fastest, Costliest)
- Cache Memory
- Primary Memory (RAM & ROM)
- Secondary Memory (Slowest, Cheapest)
?? Faster memory = Higher cost & lower capacity
?? 3. Types of Computer Memory
Computer memory is mainly divided into:
- Primary Memory
- Secondary Memory
- Cache Memory
- Register Memory
?? 4. Primary Memory (Main Memory)
Primary memory is the memory that is directly accessed by the CPU.
Characteristics:
- High speed
- Limited storage
- Expensive
- Mostly volatile
Primary memory stores currently running programs and data.
?? 5. Types of Primary Memory
Primary memory is classified into:
- RAM (Random Access Memory)
- ROM (Read Only Memory)
- Cache Memory
?? 6. RAM (Random Access Memory)
RAM is a volatile memory used to store data and programs that are currently in use.
Key Features:
- Data lost when power OFF
- Fast read & write
- Supports multitasking
- Direct CPU access
How RAM Works:
- Programs load from storage to RAM
- CPU accesses RAM for execution
- More RAM = Bett
er performance
?? 7. Types of RAM
(a) SRAM – Static RAM
- Very fast
- No refresh required
- Expensive
- Used as cache memory
(b) DRAM – Dynamic RAM
- Slower than SRAM
- Needs frequent refresh
- Cheap
- Used as main memory
(c) VRAM – Video RAM
- Dedicated graphics memory
- Used in GPUs
- Stores textures & frames
?? 8. SRAM vs DRAM (Important Theory)
|
Feature |
SRAM |
DRAM |
|
Speed |
Very High |
Moderate |
|
Refresh |
Not required |
Required |
|
Cost |
Expensive |
Cheap |
|
Storage |
Small |
Large |
|
Usage |
Cache |
Main Memory |
?? 9. ROM (Read Only Memory)
ROM is a non-volatile memory that stores permanent instructions needed to start a computer.
Key Features:
- Data retained after power OFF
- Mostly read-only
- Used in booting
?? 10. Types of ROM
(a) PROM
- Programmed once
- Cannot be changed
(b) EPROM
- Erased using UV light
- Reprogrammable
(c) EEPROM
- Electrically erasable
- Selective erase possible
(d) Flash ROM
- Faster version of EEPROM
- Used in USB, SSD, memory cards
?? 11. Cache Memory
Cache memory is a small, high-speed memory placed between CPU and RAM.
Purpose:
- Reduce access time
- Increase CPU speed
- Store frequently used data
?? 12. Levels of Cache Memory
Cache memory is divided into three levels:
L1 Cache
- Fastest
- Smallest
- Inside CPU core
L2 Cache
- Slower than L1
- Larger size
L3 Cache
- Largest
- Shared among cores
?? 13. Register Memory
Register memory is the fastest memory located inside the CPU.
Characteristics:
- Very small
- Extremely fast
- Stores instructions & addresses
Types of Registers:
- Program Counter (PC)
- Instruction Register (IR)
- Memory Address Register (MAR)
- Memory Data Register (MDR)
?? 14. Secondary Memory
Secondary memory stores data permanently and is not directly accessed by CPU.
Characteristics:
- Non-volatile
- Large capacity
- Slow but cheap
?? 15. Types of Secondary Memory
Magnetic Storage:
- Hard Disk Drive (HDD)
- Magnetic Tape
Optical Storage:
- CD
- DVD
- Blu-ray Disc
Flash Storage:
- SSD
- Pen Drive
- Memory Cards
Cloud Storage:
- Google Drive
- OneDrive
- Dropbox
?? 16. RAM vs ROM (Theory Comparison)
|
RAM |
ROM |
|
Volatile |
Non-volatile |
|
Temporary |
Permanent |
|
Faster |
Slower |
|
Used during execution |
Used during boot |
|
Read & Write |
Read only |
?? 17. Important Teaching Points
- Cache improves system speed
- RAM affects multitasking
- ROM stores firmware
- SSD is faster than HDD
- Memory hierarchy balances cost & speed