Why are anticausal systems even defined?

So, anticausal systems are defined not because one can exhibit one in reality (and not likely to be real-time), but because they are useful models, like instantaneous systems, or infinite precision computations, that are unlikely as well ("All models are wrong, but some are useful").

1. What is difference between non causal and Anticausal?
2. What is causal and anticausal system?
3. What is an Anticausal signal?
4. How do you determine the causality of a system?

What is difference between non causal and Anticausal?

A system that has some dependence on input values from the future (in addition to possible dependence on past or current input values) is termed a non-causal or acausal system, and a system that depends solely on future input values is an anticausal system.

What is causal and anticausal system?

A causal system is one whose output depends only on the present and the past inputs. A noncausal system's output depends on the future inputs. In a sense, a noncausal system is just the opposite of one that has memory.

What is an Anticausal signal?

Condition for Anti-Causal Signal: A signal which posses zero value for all positive value of time, but has amplitude which is greater then zero for all negative value of time, then the signal is known as anti-causal signal.

How do you determine the causality of a system?

A system is said to be causal if its output depends upon present and past inputs, and does not depend upon future input. For non causal system, the output depends upon future inputs also. For present value t=1, the system output is y(1) = 2x(1) + 3x(-2).