11 · The Command Line
Ctrl-C / Ctrl-D
Interrupt, and end-of-input
Ctrl-C usually sends SIGINT to the foreground process; programs may handle or ignore it. Ctrl-D sends an end-of-input character when the terminal is reading input, and Ctrl-Z usually suspends the foreground job.
Concrete example
Press Ctrl-C to request that a running command stop; if it does not, inspect the process before escalating.
Why it matters
The escape hatch every terminal user needs on day one.