The D notation uses a differential operator denoted as . When applied to a function , it is defined as

Higher derivatives are denoted as “powers” of D. For example, is the th derivative of . 1

D notation can be useful when studying differential equations. For example, can be expressed compactly as .

The differential operator is the inverse of the integral operator, so we can use the operator to represent integration. Use of operator for integration generates some subtle mathematical difficulties because the operators and do not commute. 2

Footnotes

  1. Notation for differentiation - Wikipedia

  2. Linear Systems and Signals 1.8