Signal

Signal is a beep or tone from a computer’s speaker or a prompt displayed on screen that tells a user that the computer is ready to receive input.

Two main types of signals encountered in practice are analog and digital. Digital signal results from approximating an analog signal by its values at particular time instants. Digital signals are quantized, while analog signals are continuous.

Sources:

Dictionary of Computer and Internet Terms (Vol. 1) John C. Rigdon, 2016 – 1471 c. – 1162

Kaliappan Gopalan Introduction to Signal and System Analysis. - 2012 г. – 655