Which command interrupts a program that is in the foreground?

• A. ctrl + z
• B. bg %2
• C. fg %1
• D. ctrl + c

Answer: (D)

When a program is running in the foreground, the terminal has a built-in way to stop it quickly: sending an interrupt signal. Pressing Ctrl+C sends SIGINT to the current foreground process group. The default action for SIGINT is to terminate the program, though a program can choose to handle or ignore it if it sets up a signal handler. This makes Ctrl+C the standard way to interrupt or cancel a running command.

In contrast, Ctrl+Z sends a suspend signal (SIGTSTP), which pauses the program and stops it in place, leaving it as a stopped job that can be resumed later. The commands to move jobs between foreground and background (such as putting a stopped job in the background with a suspend, then resuming with bg or bringing to the foreground with fg) are about job control, not the immediate interruption of a foreground process. Therefore, the key combination that interrupts a foreground program is Ctrl+C.