Computer components and embedded systems
| English | Chinese | Pinyin |
|---|---|---|
| embedded system | 嵌入式系统 | qiàn rù shì xì tǒng |
| output devices | 输出设备 | shū chū shè bèi |
| input devices | 输入设备 | shū rù shè bèi |
| primary memory | 主存储器 | zhǔ cún chǔ qì |
| RAM | 随机存取存储器 | suí jī cún qǔ cún chǔ qì |
| ROM | 只读存储器 | zhī dú cún chǔ qì |
| secondary storage | 辅助存储器 | fǔ zhù cún chǔ qì |
| firmware | 固件 | gù jiàn |
What's inside a computer
- Every general-purpose computer is built from the same four blocks.
- Understanding them explains how a program runs.
- We finish with embedded systems 嵌入式系统 — computers hidden inside other devices.
Tap the blocks of a computer system
Explore the four blocks plus the CPU. Data flows input → processing → output, while primary memory holds the running program and secondary storage keeps it for later.
Input and output devices 输出设备
- Input devices 输入设备 get data in: keyboard, mouse, microphone, scanner, sensors.
- Output devices give results out: monitor, speakers, printer, actuators.
- Input → processing → output is the basic flow of any computer task.
A monitor is a common output device.
Which of these is an input device?
A scanner brings data in. Monitors, speakers and printers are output devices.
Memory and storage
- Primary memory 主存储器 is fast memory the processor reaches directly — RAM 随机存取存储器 and ROM 只读存储器. It holds the running program and its data.
- Secondary storage 辅助存储器 is slower but larger and keeps data without power — hard disk, SSD, optical disc, USB stick.
- The CPU can't run a program straight from secondary storage — it is loaded into primary memory first.
An opened hard disk: the actuator arm carries the read/write head over a spinning platter.
A platter stores data in concentric tracks, each divided into sectors.
Optical discs (CD/DVD/Blu-ray) are another form of secondary storage, read by a laser.
Match each part to its category.
Keyboard = input, monitor = output, RAM = fast primary memory, SSD = non-volatile secondary storage.
Primary memory differs from secondary storage because it:
Primary memory (RAM/ROM) is fast and directly accessible by the CPU; secondary storage is slower, larger and non-volatile.
Put the steps of running a stored program in order.
The CPU can only run code from primary memory, so a program is loaded from storage into RAM first.
RAM is volatile (its contents are lost without power), while secondary storage keeps data when the power is off.
That is why your work must be saved to storage — RAM only holds it while the computer is on.
Embedded systems
- An embedded system is a computer built into another device to do one fixed job (washing machine, microwave, car engine unit, thermostat).
- Benefits: optimised for one task (low power, small, cheap), reliable, fast to start.
- Drawbacks: limited to that one task, hard to update (special tools for its firmware 固件), often not repairable, sometimes weak security.
- Memory types: Static RAM (SRAM, cache) vs Dynamic RAM (DRAM, main memory); and Programmable ROM (PROM), Erasable Programmable ROM (EPROM) and Electrically Erasable Programmable ROM (EEPROM). Also: the optical disc reader/writer, the virtual reality headset, and control systems that act on sensor data.
An embedded system is:
Embedded systems (in a washing machine, microwave, car…) are dedicated to a single fixed task.
A drawback of an embedded system is that it:
Being dedicated makes it efficient but inflexible — it cannot easily be repurposed and its firmware is hard to update.
You've got it
- four blocks: input, output, primary memory, secondary storage
- primary (RAM/ROM) = fast, CPU-direct, holds the running program
- secondary = slower, larger, non-volatile (HDD/SSD/optical/USB)
- an embedded system = a computer built into a device for one fixed job