Continuous vs. Discrete signals

• A signal, of which a sinusoid is only one example, is a sequence of numbers.
• A continuous-time signal is an infinite and uncountable set of numbers, as are the possible values each number can have.
  • between a start and end time, there are infinite possible values for time $t$ and instantaneous amplitude, $x(t)$.
• When continuous signals are brought into a computer, they must be digitized or discretized (i.e., made discrete).
• In a discrete-time signal, the number of elements in the set, as well as the possible values of each element, is finite, countable, and can be represented with computer bits, and stored on a digital storage medium.