AS · Practice questions · Input, output and storage devices

Describe the steps.

Six original Cambridge-style questions on why each kind of hardware is needed, how devices operate and why buffers are used, with mark-scheme style solutions.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

How to earn the marks

One step, one mark.

Operations: write each device's operation as separate steps in the order they happen.
Use the key words: drum, charge, toner, fuser; platter, track, sector, head; floating gate; pits and lands.
Justify, do not just name: secondary storage is needed because it is non-volatile and larger.
Buffers: different speeds, temporary memory, CPU freed for other tasks, interrupt when empty.

Explain

[2 marks]

Explain why a computer needs both primary memory and secondary storage.

Primary memory (RAM) is accessed directly by the CPU, so the programs and data currently in use must be loaded into it. ✓
RAM is volatile (and smaller), so secondary storage is needed to keep programs and files permanently when the power is off. ✓

Explain

[5 marks]

Describe how a laser printer prints a page.

The rotating drum is given an electrostatic charge. ✓
A laser beam scans the drum, changing the charge to form an electrostatic image of the page. ✓
Charged toner is attracted to the image on the drum. ✓
Charged paper passes over the drum and attracts the toner off it. ✓
A fuser (heated rollers) melts the toner onto the paper; the drum is discharged ready for the next page. ✓

Explain

[4 marks]

Describe how a speaker produces sound from digital data stored in a computer.

The digital data is converted to an analogue signal by a DAC (and amplified). ✓
The varying current passes through a coil, making it an electromagnet. ✓
The coil is attracted and repelled by a permanent magnet, so it moves back and forth. ✓
The coil moves a cone, which vibrates the air to produce sound waves. ✓

Apply

[3 marks]

A company is choosing between a solid-state drive and a magnetic hard disk drive for a laptop that sales staff carry between customers. Recommend one, giving two reasons.

Solid-state drive. ✓
It has no moving parts, so it is more robust if the laptop is dropped or moved while in use. ✓
Any one of: faster access, because there is no head movement or rotational delay; lighter; uses less power, so the battery lasts longer. ✓

Explain

[4 marks]

Describe how a virtual reality headset gives the user the impression of being inside a 3D scene.

There is a separate screen (or half a screen) for each eye. ✓
Each eye is shown a slightly different image, so the brain sees depth (stereoscopic 3D); lenses focus the images. ✓
Sensors such as a gyroscope and accelerometer detect the movement of the head. ✓
The images are updated in real time to match the head movement. ✓

Analysis

[3 marks]

A student says: "A printer buffer makes the printer print faster." Explain why this is wrong and state the real benefit.

The printer still prints at its own (slow) speed. ✓
The buffer stores data sent quickly by the CPU, so the CPU does not have to wait for the printer. ✓
The CPU is free to do other tasks and is only interrupted when the buffer needs refilling. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.