Learning objective
Secondary storage devices: Explain the need for secondary storage within a computer system. Know the main characteristics, purposes, suitability and understand the principles of operation of the following devices: • hard disk • optical disk • solid-state disk (SSD). SSD = NAND flash memory + a controller that manages pages, and blocks and complexities of writing. Based on floating gate transistors that trap and store charge. A block, made up of many pages, cannot overwrite pages, page has to be erased before it can be written to but technology requires the whole block to be erased. Lower latency and faster transfer speeds than a magnetic disk drive. Compare the capacity and speed of access of various media and make a judgement about their suitability for different applications. 80
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External hardware devices
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Secondary storage devices
Aqa A Level Computer ScienceFundamentals of computer organisation and
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Quick explanation
Secondary storage devices: Explain the need for secondary storage within a computer system. Know the main characteristics, purposes, suitability and understand the principles of operation of the following devices: • hard disk • optical disk • solid-state disk (SSD). SSD = NAND flash memory + a controller that manages pages, and blocks and complexities of writing. Based on floating gate transistors that trap and store charge. A block, made up of many pages, cannot overwrite pages, page has to be erased before it can be written to but technology requires the whole block to be erased. Lower latency and faster transfer speeds than a magnetic disk drive. Compare the capacity and speed of access of various media and make a judgement about their suitability for different applications. 80
- This point belongs to External hardware devices, especially Secondary storage devices.
- You need to be able to secondary storage devices: Explain the need for secondary storage within a computer system. Know the main characteristics, purposes, suitability and understand the principles of operation of the following devices: • hard disk • optical disk • solid-state disk (SSD). SSD = NAND flash memory + a controller that manages pages, and blocks and complexities of writing. Based on floating gate transistors that trap and store charge. A block, made up of many pages, cannot overwrite pages, page has to be erased before it can be written to but technology requires the whole block to be erased. Lower latency and faster transfer speeds than a magnetic disk drive. Compare the capacity and speed of access of various media and make a judgement about their suitability for different applications. 80.
- Use the linked flashcards and practice questions to check recall, then practise applying the idea in an exam-style answer.
Why it matters
This objective helps connect Secondary storage devices to exam-style questions, flashcards, and revision notes for External hardware devices.
Quick student answer
What is the main reason a computer system needs secondary storage?
Direct answer
Secondary storage provides persistent storage for data and programs within a computer system.
Key terms
- Latency: The delay before a storage device begins to provide access to requested data; an SSD has lower latency than a magnetic disk drive.
- Block: A unit of SSD storage made up of many pages; the whole block must be erased when a page within it needs to be erased.
Common trap
Confusing pages and blocks: A page must be erased before it can be written to, but the technology requires the whole block, containing many pages, to be erased.
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