Continuous-time systems
Continuous-Continuous systems

1.Tree swaying in the wind:
Wind - described by its speed, direction - is a continuous-time input.
Movement of branches is continuous-time output signal.

Discrete-time systems
Discrete-Discrete systems

1.Logic circuits:
Discrete logic inputs are processed to give discrete logic outputs.

Hybrid systems
Continuous-Discrete systems

1.Eye: sees continuous image, but sends a discrete map to the brain

2.Computer microphone: Sampler converts a continuous time signal into a discrete time signal.(Sampler forms an important system in today’s digital world - we shall look at this in great detail later in the course)

Hybrid systems
Discrete-Continuous systems

1.Brain : gets a discrete map from the eye, and completes a smooth, continuous picture

2.Computer speaker and sound card - a digital music output given by the computer is smoothed out and played as a continuous waveform.