Why is secondary storage needed, and how do magnetic, optical and solid-state storage compare?
The need for secondary storage, the characteristics of magnetic, optical and solid-state storage, and calculating storage requirements and capacity.
A focused answer to the WJEC GCSE Computer Science Unit 1 content on secondary storage, covering why secondary storage is needed, the characteristics, advantages and disadvantages of magnetic, optical and solid-state storage, and calculating how many files of a given size fit in a given storage capacity.
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What this topic is asking
WJEC wants you to know why secondary storage is needed, the characteristics of magnetic, optical and solid-state storage, and how to calculate storage requirements. This is part of the Hardware content in Unit 1 of WJEC GCSE Computer Science (3500).
Why secondary storage is needed
Magnetic storage
Optical storage
Solid-state storage
Calculating storage requirements
To work out how many files of a given size fit in a storage device, make sure both are in the same unit, then divide the capacity by the file size.
Try this
Q1. State one reason why a computer needs secondary storage as well as RAM. [1 mark]
- Cue. RAM is volatile, so secondary storage keeps programs and files permanently when the power is off.
Q2. A hard disk has a capacity of . How many films can it store? [2 marks]
- Cue. ; films.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC-style Unit 14 marksCompare solid-state storage (SSD) with magnetic hard disk storage (HDD), giving one advantage and one disadvantage of solid-state storage.Show worked answer →
A Unit 1 storage comparison. Solid-state storage uses flash memory with no moving parts, while a magnetic hard disk stores data on spinning platters read by a moving head (1 mark for the technology difference). An advantage of SSD is that it is much faster to read and write and is more durable and silent because it has no moving parts (1 mark). A disadvantage is that SSDs are usually more expensive per gigabyte, so they offer less capacity for the same price than magnetic disks (1 mark). A valid alternative advantage is lower power use; a valid alternative disadvantage is a limited number of write cycles (1 mark). Markers reward the no-moving-parts point plus a sensible advantage and disadvantage. A common error is to say SSDs always store more data, which is not the comparison being made.
WJEC-style Unit 13 marksA memory card has a capacity of . Each photo is . Calculate how many photos it can store. Show your working.Show worked answer →
A Unit 1 capacity calculation. Convert the capacity to the same unit as the file: (1 mark). Divide by the file size: photos (1 mark for the division, 1 mark for the answer). Markers reward converting GB to MB and the correct division. A common error is to forget to convert the units, or to multiply instead of divide.
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