Input, Output and Storage

What Input, Output and Storage covers

Input, Output and Storage is examined on component 01 of OCR Computer Science, Computer systems. 46 recall questions across 4 subtopics.

The 4 subtopics

Each one has its own page.

• Choosing input and output devices for a problemRecall questions on choosing input and output devices for a problem, including barcode scanners, optical mark and character recognition, touchscreens, graphics tablets, devices for users who cannot use their hands or cannot see, printers and actuators.Open →
• Magnetic, flash and optical storageRecall questions on how magnetic hard disks, flash and optical discs store data, seek and rotational delay, flash wear, Blu-ray capacity, R and RW discs, and comparing the three for speed, cost, capacity, durability and typical use.Open →
• RAM and ROMRecall questions on what RAM and ROM hold, why RAM is volatile, why ROM must be non-volatile, EEPROM and flash ROM, what more RAM improves, ROM in embedded devices, and why RAM is described as random access.Open →
• Virtual storage and disk thrashingRecall questions on how virtual memory uses secondary storage, page faults and page replacement, disk thrashing and how to cure it, the two meanings of virtual storage, and why cache and virtual memory are different ideas.Open →

What you need to know

Answer each one before you reveal it.

Take Input, Output and Storage further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Magnetic storage vs Flash storage

  Magnetic storage: storage that records data by magnetising regions of a spinning coated platter. Flash storage: storage that holds data as charge trapped on the floating gate of a transistor.

• RAM vs ROM

  RAM: volatile working memory holding the programs and data currently in use. ROM: non-volatile memory whose contents survive power loss and are not normally written to.

• Virtual memory vs Disk thrashing

  Virtual memory: a region of secondary storage used to hold pages that will not fit in main memory. Disk thrashing: the state where a machine spends more time swapping pages than doing useful work.

Questions from this topic

Each one with the model answer underneath.

1. 1

   How should you decide which input device suits a particular problem?

   Model answer

   Match the characteristics of the device to the demands of the problem: how much data must be entered and how quickly, how accurate the entry has to be, the physical environment the device will live in, who the users are and what they can physically do, the cost and durability required, and what form the data is already in. A good justification always names the property of the device and links it to a stated requirement of the problem.

2. 2

   Which input device suits a supermarket checkout, and why?

   Model answer

   A barcode scanner. A laser or camera reads the pattern of bars and spaces, which is far quicker than typing a product code and removes typing errors entirely; the code is already printed on the goods so nothing has to be prepared; the scanners are cheap and hard-wearing enough for constant use. The till uses the code to look up the price and update the stock count automatically. A keypad is still needed as a fallback for damaged barcodes and for loose items.

3. 3

   A national testing organisation must mark twenty thousand multiple choice answer sheets. What input device, and what limitation does it have?

   Model answer

   Optical mark recognition. The reader detects the position of pencil marks in pre-printed boxes on the form, processing thousands of sheets an hour with almost no errors and no operator typing anything. The limitation is that it only works with specially designed forms, marks must be in the right place and made with the right kind of pencil, and it reads only the presence of a mark, not any handwriting.

4. 4

   A company wants to turn a filing cabinet of printed letters into searchable text. Which devices and techniques?

   Model answer

   A sheet-feed or flatbed scanner to capture each page as an image, followed by optical character recognition software to convert the shapes of the printed characters into character codes. Scanning alone gives only a picture, which cannot be searched or edited; OCR is what makes the text usable. Accuracy depends on the quality of the print, and OCR output has to be checked, unlike optical mark recognition which is essentially exact.

5. 5

   Why is a touchscreen the right input device for a self-service ticket machine at a railway station?

   Model answer

   It combines the display and the input in one sealed unit, so there is no separate keyboard or mouse to be stolen, vandalised or damaged by weather; it tolerates dirt and wet hands; it needs no training, because the user simply touches what they can see; and the controls can be redrawn at every step to show only the choices that are currently relevant. Its weaknesses are that it is slow for entering long text and that an alternative must be offered for users who cannot see or reach the screen.

6. 6

   Which input device would you specify for a professional digital illustrator?

   Model answer

   A graphics tablet with a pressure-sensitive stylus. Pressure and tilt are captured as well as position, so the software can vary line width and opacity as a real brush would; the absolute positioning and high resolution give far finer control than a mouse, which reports only relative movement. The illustrator draws with a hand movement they already have years of practice in.

What is inside Levo

Six ways to work the same material.

Input, Output and Storage revision questions

What does Input, Output and Storage cover in OCR A-Level Computer Science?

4 subtopics: choosing input and output devices for a problem, magnetic, flash and optical storage, ram and rom and virtual storage and disk thrashing. Each one has its own page with questions and model answers.

How is Input, Output and Storage organised?

By the OCR H446 specification, subtopic by subtopic, so it matches the order you are taught it in.