Fundamentals 3 min read

How Keyboard Input Traverses from Hardware to Software in Unix-like Systems

When a key is pressed, the keyboard controller generates an interrupt that pauses the CPU, invokes the interrupt handler and driver to translate the scan code into a character, writes it to a device file, which the X server reads and forwards via IPC to the focused window.

Java Tech Enthusiast
Java Tech Enthusiast
Java Tech Enthusiast
How Keyboard Input Traverses from Hardware to Software in Unix-like Systems

When a key is pressed, the keyboard controller detects the event and generates an interrupt signal for the CPU.

The CPU pauses the current task, jumps to the interrupt handler (e.g., do_irq), and invokes the keyboard driver.

The driver translates the scan code (e.g., the letter “a”) and writes it to a device file, making the input visible to the kernel.

In Unix-like systems, the X server reads the device file and, via inter‑process communication (IPC), forwards the key event to the window that has focus.

IPCdevice fileInterruptkeyboardOSUnix
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