01They Don't Actually "Read Thoughts"
You want to type a letter on the screen, so you press a key; You want to open an icon, so you move the mouse and click.
It might seem like the keyboard and mouse "know what you want to do," but that's not actually the case. They only detect your physical actions and convert these actions into data that the computer can receive.
Human Action
Key presses, movements, clicks, scrolling
Device Detection
Converts actions into electronic signals and data
Computer Processing
Operating system and programs interpret this input
02What Happens When You Press a Key?
Underneath a keyboard, each key doesn't directly have a separate wire connecting to the computer. Common keyboards internally use a set of circuits arranged in a grid-like structure to detect key presses.
You Press a Key
For example, pressing the A key
Keyboard Detects Position
Controller determines which key was pressed
Converts to Key Information
Device encodes "which key, pressed or released" into data
03How Does a Mouse Know It Has Moved?
Modern optical mice have a light source and sensor on the bottom. They continuously observe tiny changes on the desktop surface and calculate how much the mouse has moved relative to its position.
Optical Mouse
Mice usually don't tell the computer: "I'm now at pixel 500,300 on the screen."
More commonly, they tell the computer: "I moved a bit to the right and a bit upward."
04How Is This Information Sent to the Computer?
After keyboards and mice detect actions, they still need to send the data to the computer. Common methods include USB wired connections and wireless connections.
USB
Data is transmitted to the computer through cables
Wireless
Transmitted via Bluetooth or wireless receiver
Devices Send "Input Reports"
Common USB keyboards and mice belong to HID (Human Interface Device). They report key presses, buttons, and movement information to the computer in specified formats.
The underlying details of different devices and connection methods are not exactly the same. Here we're introducing the basic working model of common personal computer keyboards and mice.
05How Do Computers Convert Input into Text and Actions?
After devices send data to the computer, it's not yet accurate to say "the program has received a letter." The operating system and drivers first process device input, then deliver appropriate events to running programs.
Keyboard / Mouse
Reports key presses, movements, and buttons
Operating System / Drivers
Recognizes devices and processes input
Applications
Execute their own functions based on input
Keyboard Input
The same key press might input characters in a text editor; represent "move forward" in a game; or represent another command in a shortcut.
Mouse Input
Movement data can change cursor position, while clicks are interpreted by the current program as selection, opening, dragging, and other operations.
06Understanding the Complete Process with an "Input A" Example
Suppose you're in English input mode and press the A key in a text editor. We can simplify the entire process into the following path:
Finger Presses Key
You press the A key
Keyboard Detection
Knows a certain key was pressed
Send to Computer
Send data via USB or wireless
Software Processing
System interprets input based on layout, key state, etc.
Display Character
Text editor finally displays A or a
What You've Learned
- Keyboards and mice can't read human thoughts; they can only detect actions like key presses, movements, and clicks.
- Keyboards detect which keys are pressed or released and encode this information into data.
- Optical mice observe surface changes and calculate relative movement.
- Keyboards and mice can send data to computers via USB, Bluetooth, or wireless receivers.
- Common keyboards and mice belong to HID (Human Interface Device).
- Operating systems and programs continue to interpret input, so the same key can have different effects in different programs.
- Input devices are responsible for "reporting actions," while software is responsible for "determining what these actions mean."
Next Question: After keyboards and mice send information to the computer, how do screens display text, images, and game graphics? Next article: How Do Screens Display Images?