Data Storage - SS1 Digital Technologies Lesson Notes
SS1 Digital Technologies Lesson Notes
Introduction to Digital Memory
In our previous lesson, we learned how the CPU executes code. However, the CPU cannot hold large amounts of information internally. To make a computer functional, it needs a way to store data. In digital systems, data storage refers to the hardware technologies that record, retain, and preserve digital bits (0s and 1s) either temporarily or permanently.
• Volatile Memory is temporary storage that requires a continuous electrical current to maintain its data. The moment the device is switched off, everything stored inside it vanishes.
• Non-Volatile Memory is permanent storage that safely retains its recorded data even when the device is completely powered down.
Primary Storage vs. Secondary Storage
Computer systems organize their memory hierarchy into two distinct categories based on how closely they interact with the main processor:
1. Primary Storage (Main Memory)
Primary storage is directly accessible by the CPU via the internal system buses. It holds data and software instructions that are currently being actively processed. It features exceptionally high access speeds but carries limited capacity.
- RAM (Random Access Memory): Volatile. RAM acts as the computer's short-term workspace. When you open an app or a document, it is loaded from your slow hard drive into your fast RAM so the CPU can use it smoothly. Turning off the PC wipes RAM clean.
- ROM (Read-Only Memory): Non-Volatile. ROM holds essential, unchangeable system start-up files. It contains the BIOS / UEFI software instructions that tell the computer how to check its components and boot up safely when you first click the power switch.
2. Secondary Storage (Auxiliary Memory)
Secondary storage is not directly mapped to the CPU. It is completely non-volatile and provides large storage spaces to save your operating system files, videos, documents, and games permanently.
Types of Secondary Storage Media
Modern computing hardware splits permanent secondary data recording into three separate technology mediums:
| Storage Category | How It Works | Common Everyday Examples |
|---|---|---|
| Magnetic Storage | Uses spinning metal platters coated with magnetic material to read and write binary data using mechanical heads. High storage capacity but prone to physical damage if dropped. | Traditional Hard Disk Drives (HDD), old floppy disks, external magnetic backup drives. |
| Solid-State (Flash) Storage | Uses electronic microchips containing no moving parts. They operate silently, load files significantly faster than HDDs, and use less power. | Solid-State Drives (SSD), USB flash drives, phone MicroSD memory cards. |
| Optical Storage | Uses lasers to read and burn data onto reflective tracks made of microscopic pits and lands on a plastic disc surface. | CD-ROMs, DVDs, and Blu-ray discs. |
Summary of Memory Characteristics
- Speed: Primary storage (RAM) is incredibly fast compared to secondary storage (HDDs/SSDs), because it sits closer to the CPU pathways.
- Capacity: Secondary storage provides massive capacities (e.g., 1 Terabyte SSD) to hold physical user libraries, whereas RAM installations are small (e.g., 8 Gigabytes or 16 Gigabytes).
- Cost: Per gigabyte, primary memory is far more expensive to manufacture than auxiliary secondary disks.
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