⌨️ 输入输出设备：电脑城的城门⌨️ I/O Devices: the gates of Computer City

上一片里，冰箱（存储设备）把照片、作业都存稳了。可东西从哪儿进来？结果又怎么交到你手上？这回把整台电脑看成一座“电脑城”，先看城门。 Last leaf, the fridge (storage) kept your photos and homework safe. But how does anything get in — and how do results get back to you? This time, picture the whole computer as a walled Computer City. First stop: the gates.

第 1 步：两道城门，一进一出Step 1: Two gates — one in, one out

电脑城有城墙围着，东西只能走城门。Computer City has walls, so everything must pass through a gate.

电脑城的两道城门：输入与输出 — 输入设备管“进”：键盘、鼠标、麦克风、摄像头，把你的动作送进城。输出设备管“出”：显示器、音箱、打印机，把结果送回给你。 Input devices handle “in”: keyboard, mouse, microphone and webcam carry your actions into the city. Output devices handle “out”: monitor, speaker and printer bring the results back to you.

可城里只认 0 和 1，你按的键怎么进去？But the city only speaks 0s and 1s. How does your keypress get in?

第 2 步：每道城门都是翻译官Step 2: Every gate is a translator

按键 A 变成 01000001，经 CPU 处理后显示为屏幕上的 A — 按下 A 键，它被翻译成编码 01000001 送进城（还记得字符编码吗？）。CPU 处理完，显示器再把编码翻译回来，亮出字母 A。 Press A and it's translated into the code 01000001 on the way in (remember character encoding?). When the CPU is done, the monitor translates the code back and lights up the letter A.

有没有一道门，既能进又能出？Is there a gate that goes both ways?

第 3 步：双向门，一门两用Step 3: Two-way gates do both jobs

触摸屏与带麦耳机：既是输入也是输出 — 触摸屏就是双向门：手指点它是输入，它亮出画面是输出。带麦耳机也一样：麦克风管进，耳机管出。手机上几乎全是这种门。 A touchscreen is a two-way gate: your tap is input, the picture it shows is output. A headset with a mic works the same way: the mic goes in, the earphones come out. Phones are full of gates like these.

🎮 城门分拣员（30 秒）🎮 Your turn: gate sorter (30 seconds)

道理讲完了。先按一个键，看它穿过两道城门；再把 9 个设备放进对的篮子，小心双向门！Theory done. First press a key and watch it cross both gates; then drop 9 devices into the right baskets — watch out for two-way gates!

一句话记住它：输入设备把你的动作翻译成 0 和 1 送进电脑，输出设备把结果翻译回来给你看、给你听；触摸屏两样都干。 Remember it in one line: input devices translate your actions into 0s and 1s and carry them in; output devices translate results back for you to see and hear; a touchscreen does both.

输入：键盘、鼠标、麦克风、摄像头，把动作送进城Input: keyboard, mouse, mic and webcam carry your actions in 输出：显示器、音箱、打印机，把结果送出城Output: monitor, speaker and printer carry results out 双向：触摸屏、带麦耳机能进也能出；每道门都是翻译官Two-way: touchscreen and headset do both; every gate is a translator

内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。 Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.