1, a ladder function with infinite jump discontinuity, that is, a ladder function (also known as an integer function).

2. In mathematics, real number function is called stage function (or step function), so it can be written as a linear combination of finite interval index functions. The informal view is that a stage function is a piecewise constant function, but it contains many stages but is limited.

3. Assume that x is an arbitrary real number. The maximum certificate that does not exceed X is called the integer part of X, and is recorded as [x]. For example, [5/7] = 0, [π] = 3, [- 1] =- 1, [-3.5] =-4. Take x as the variable.