Storage and peripheral devices
| English | Chinese | Pinyin |
|---|---|---|
| buffer | 缓冲 | huǎn chōng |
| magnetic hard disk | 磁盘 | cí pán |
| tracks | 磁道 | cí dào |
| sectors | 扇区 | shàn qū |
| solid-state drive | 固态硬盘 | gù tài yìng pán |
| optical disc | 光盘 | guāng pán |
| ADC | 模数转换器 | mó shù zhuǎn huàn qì |
Storing and moving data
- Secondary storage keeps your files safe when the power is off.
- Different technologies trade speed, cost and durability.
- We also meet some key peripherals and the handy buffer 缓冲.
Network route lab
Follow data from a device through network hardware and protocols.
Magnetic, solid-state and optical storage
- Magnetic hard disk 磁盘 (HDD) — data on spinning platters with tracks 磁道 and sectors 扇区; a read/write head magnetises tiny regions. Cheap per GB, but slower with moving parts.
- Solid-state drive 固态硬盘 (SSD) — data as charge in transistors (flash), no moving parts. Faster, tougher, lower power, but dearer per GB and each cell wears out after many writes.
- Optical disc 光盘 (CD/DVD/Blu-ray) — a laser reads tiny pits; writing changes the surface's reflectivity.
Inside an SSD: data is stored in flash memory chips, with no moving parts
A flatbed scanner: an input device that turns a paper page into a digital image
How does an SSD differ from a magnetic hard disk?
SSDs store charge in flash transistors — no moving parts, faster and tougher, but dearer per GB and cells wear out.
How does an optical disc (CD/DVD) store and read data?
A laser reads the pattern of pits; writing uses a stronger laser to change reflectivity.
Match each secondary-storage type to how it stores data.
The three storage technologies — magnetic, solid-state and optical — differ in the physics they use to hold a bit.
Other peripherals
- Laser printer — toner sticks to a charged drum, transfers to paper, melted on by a fuser. Fast and sharp.
- 3D printer — builds an object layer by layer (melted filament, or UV-cured resin).
- Touchscreen — resistive (two layers pressed; works with anything, less accurate) or capacitive (a finger disturbs a charge field; accurate, multi-touch).
- Microphone turns sound into a signal, digitised by an ADC 模数转换器; a speaker does the reverse.
A mouse: a pointing input device
A microphone's analogue signal must pass through which component to be stored digitally?
An ADC converts the continuous analogue signal into digital samples the computer can store.
Put the steps of recording sound digitally in order.
A microphone is a transducer (sound → voltage); the ADC then turns that analogue signal into storable digital samples.
A capacitive touchscreen supports multi-touch and responds to a conductive finger, while a resistive one needs physical pressure.
Capacitive screens sense a finger disturbing a charge field (multi-touch, accurate); resistive screens work by pressing two layers together.
Buffers
- A buffer is memory that holds data temporarily while it moves between devices of different speeds.
- Example: the CPU writes a document to the printer buffer quickly, then is free to do other work while the printer prints from the buffer at its own pace.
- Buffers stop the fast device having to wait for the slow one (also used in streaming and disk access).
A keyboard: a common input device for typing text and commands
The purpose of a buffer is to:
A buffer lets a fast device (CPU) hand off data and carry on, while a slow device (printer) consumes it at its own pace.
You've got it
- HDD = magnetic platters (cheap, moving parts); SSD = flash (fast, no moving parts); optical = laser + pits
- a touchscreen is resistive (any object) or capacitive (finger, multi-touch)
- a microphone needs an ADC to digitise its analogue signal
- a buffer temporarily stores data between devices of different speeds