Top-down design is a phrase from the field of software engineering, and refers to a strategy used in designing a product, such as a software program.

Top-down design in software programming is similar to the concept of outlines in the design of documents, in that the structure of the document, or the software, is the central emphasis. Software top-down design, however, is unique from a document that is written once and is not changed. Software undergoes multiple revisions and improvements following its initial design. Top-down design makes the maintenance process easier.

A design project is divided into a series of hierarchies, or levels, ranging from the entire project to the smallest aspect of the project. These project components are arranged in a logical progressive order and relationships are established--what must be done at one level before the next level can be accomplished, for example. In principle...