GCSE > Computer Science > OCR > GCSE Computer Science > COMPUTER SYSTEMS: Memory and storage > Secondary storage
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COMPUTER SYSTEMS: Encoding and compression

COMPUTER SYSTEMS: Network topologies

COMPUTER SYSTEMS: Wired and wireless networks, protocols, and layers

COMPUTER SYSTEMS: Threats to computer systems and networks

COMPUTER SYSTEMS: Operating systems and utility software

ALGORITHMS AND PROGRAMMING: Types of data

ALGORITHMS AND PROGRAMMING: Producing robust programs

ALGORITHMS AND PROGRAMMING: Designing, creating, and refining algorithms

ALGORITHMS AND PROGRAMMING: Artificial Intelligence (AI)

  • Long-term storage: stores program instructions and data until needed by CPU. This is provided by HDD, SSD, and optical media (CD, DVD). Common types of secondary storage include optical, magnetic, and solid state drives.
  Optical Magnetic Solid state
Examples CD, DVD, Blu-ray Hard Disk Drive (HDD) SSD, USB stick, SD card
Capacity Low (up to 50 GB) Very high (TBs) Medium to high (GBs–TBs)
Speed Slow Moderate Very fast
Portability High (small, light) Moderate (portable HDDs) Very high
Durability Low (easily scratched) Low (moving parts) High (no moving parts)
Reliability Moderate Moderate High
Cost Very low Low (cheap per GB) High (expensive per GB)

  Advantages Disadvantages
Optical Cheap, portable, good for sharing or backups Low capacity, slow, easily damaged
Magnetic Large storage, affordable Slower than SSDs, vulnerable to physical damage
Solid state Fast access, durable, silent, energy efficient Higher cost, limited write cycles (especially USBs)
  • Virtual memory is a technique used by operating systems to extend primary/RAM storage when it is full by temporarily storing data from RAM sections (pages) in a file (pagefile) on secondary storage. This frees up RAM for other processes, enabling more programs to run simultaneously. However, since secondary storage is much slower than RAM, this can lead to reduced system performance

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