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SSC CGL Preparation – Day 4
Computer Basics: Memory – Types of Memory
🧠 What is Computer Memory?
Computer memory refers to the devices used to store data or programs temporarily or permanently. It plays a vital role in storing instructions and processing data. Computer memory is broadly classified based on speed, capacity, and cost.
🔰 Types of Memory in Computers
Memory is mainly divided into two categories:
1️⃣ Primary Memory (Main Memory)
- Directly accessible by the CPU
- Faster but limited in capacity
- Volatile (data lost when power is off)
🔹 RAM (Random Access Memory)
- Temporary storage used while programs are running
- Volatile memory
- Types of RAM:
- DRAM (Dynamic RAM): Needs constant refreshing
- SRAM (Static RAM): Faster, more expensive, no refreshing required
🔹 ROM (Read Only Memory)
- Non-volatile (retains data after power off)
- Stores firmware or permanent data
- Cannot be modified easily
- Types of ROM:
- PROM (Programmable ROM): Can be programmed once
- EPROM (Erasable PROM): Can be erased by UV light
- EEPROM (Electrically Erasable PROM): Can be erased using electricity
2️⃣ Secondary Memory (Storage Devices)
- Not directly accessed by CPU
- Non-volatile (retains data permanently)
- Used to store large volumes of data
Examples:
- Hard Disk Drive (HDD)
- Solid State Drive (SSD)
- CD/DVD
- Pen Drive
- Memory Card
3️⃣ Cache Memory
- Small-sized high-speed memory located close to the CPU
- Stores frequently accessed data/instructions
- Faster than RAM
- Improves overall processing speed
Cache Levels:
- L1 (Level 1): Closest to CPU, fastest, smallest
- L2 (Level 2): Slightly slower, larger than L1
- L3 (Level 3): Shared among cores, slower than L2
4️⃣ Virtual Memory
- Part of the hard drive used as if it were RAM
- Extends RAM capacity when RAM is full
- Slower than actual RAM
- Managed by the operating system
5️⃣ Flash Memory
- Non-volatile
- Used in USB drives, SSDs, memory cards
- Durable and compact
6️⃣ Register Memory
- Located within the CPU
- Extremely fast and small
- Used to store instructions, addresses, and intermediate results
🔍 Comparison Table of Memory Types
| Type | Speed | Volatility | Size | Usage |
|---|---|---|---|---|
| Registers | Fastest | Volatile | Very Small | CPU processing |
| Cache Memory | Very Fast | Volatile | Small | Speeds up CPU access |
| RAM | Fast | Volatile | Medium | Running programs |
| ROM | Medium | Non-volatile | Small | Firmware storage |
| Virtual Memory | Slow | Volatile | Large | RAM extension |
| Secondary Memory | Slow | Non-volatile | Very Large | Long-term storage |
| Flash Memory | Fast | Non-volatile | Varies | Portable storage (USB, SSD) |
💡 Key Points for SSC CGL
- RAM is volatile and used for temporary storage during program execution.
- ROM is non-volatile and stores BIOS or firmware.
- Cache memory enhances CPU speed by storing frequent instructions.
- Virtual memory is used when RAM is full to temporarily use hard disk space.
- Registers are the smallest and fastest type of memory.
- Flash memory is commonly used in portable devices.
