The controlling terminal and process-groups

A session may be allocated a controlling terminal. For every allocated controlling terminal, Job Control elevates one process group in the controlling process's session to the status of foreground process group. The remaining process-groups in the controlling process's session are background process-groups. A controlling terminal gives a user the ability to control execution of jobs within the session. Controlling-terminals play a central role in Job Control. A user may cause the foreground job to stop by typing a predefined key on the controlling terminal. A user may inhibit access to the controlling terminal by background jobs. Background jobs that attempt to access a terminal that has been so restricted will be sent a signal that typically causes the job to stop. (see ``Accessing the controlling terminal'').