The Heaviside step function, or the unit step function, usually denoted by H or θ (but sometimes u, 1 or 𝟙), is a step function, named after Oliver Heaviside (1850–1925), the value of which is zero for negative arguments and one for positive arguments. It is an example of the general class of step functions, all of which can be represented as linear combinations of translations of this one. The Heaviside function may be defined as: * a piecewise function: * using the Iverson bracket notation: * an indicator function: * the derivative of the ramp function: