A command, with or without arguments, executed in the background using &.
For simplicity, assume that if present the & is always the last thing on the line.
Example: vi &
Details: In this case, your shell must execute the command and return immediately, not
blocking until the command finishes. The distinction must be made between
backgrounding a process that does not need interactive input and one that does, e.g., the
who command vs. the vi command.
Concepts: Background execution, signals, signal handlers, process groups, asynchronous
execution.
System calls: sigset(), sigaction()
Signals: SIGTTOU