The function is used in the mathematics of control theory to represent a signal that switches on at a specified time, and which stays switched on indefinitely. It was named after the Englishman Oliver Heaviside.
We can also define an alternative form of the Heaviside step function as a function of a discrete variable n:
where n is an integer.
The discrete-time unit impulse is the first difference of the discrete-time step
This function is the cumulative summation of the Kronecker delta:
is the discrete unit impulse function.
Often an integral representation of the Heaviside step function is useful:
The value of the function at 0 can be defined as H(0) = 0, H(0) = ½ or H(0) = 1. In particular: