Context diagrams (level 0 DFDs) are diagrams that depict the entire system as a single process. A level 1 DFD describes each of the major sub-processes that comprise the whole system. A level 1 DFD can be thought of as a "exploded perspective" of the context diagram. A level 0 flowchart has the least amount of information and often has one or two steps. A level 4 flowchart has the maximum depth and might comprise hundreds of stages. Every work, no matter how little, is represented at this level.
