External hardware devices | AQA Computer Science 7517

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Input and output devices1 objectives

Input and output devices: Know the main characteristics, purposes and suitability of the devices and understand their principles of operation. Devices that need to be considered are: • barcode reader • digital camera • laser printer • RFID.

Secondary storage devices1 objectives

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

RFIDTonerLatencyBlock

Link the device to the situation: When asked which device is suitable, refer to the required operating conditions as well as naming the device.
Link the comparison to the application: When judging whether a hard disk, optical disk or SSD is suitable, compare the application's required capacity and speed of access with the characteristics of the media.

Confusing RFID with barcode scanning: State that a barcode reader uses optical scanning of printed markings, whereas RFID uses radio communication between a reader and a tag.
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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