What is the difference between the four "data flow diagrams", "system flow diagrams", "program flow diagrams" and "data flow diagrams"? What is the difference between these four?

1. Data Flow Diagram (DataFlowDiagram);

insist on more DFD, it is from the perspective of data transfer and processing, graphically to express the logical function of the system, the logical flow of data within the system and the logical process of exchange, is the main expression of structured systems analysis methodology and used to represent the software model of a graphical amplification. It is the process of depicting the flow of information and data moving from input to output undergoing transformation.

Basic elements of a data flow diagram:

2. SystemFlowchart;

The traditional tool for depicting the physical model of a system. His basic idea is to use graphical symbols in the form of a black box to depict each component of the system concept including programs, files, databases, tables, manual processes, etc., to express the flow of information between the given components, rather than to represent the control processes that process the information.

Example diagrams:

3. Flowchart of a program;

4. Diagram of the system structure of a program.

Data flow chart: the reaction to the loss of the direction, it does not take into account the timing of the relationship, mainly for business analysis, used as a detailed design. Directed line segments on the way represents the data flow.

System flow chart: reaction to the main framework.

Program flow chart: program logic describes the control flow in the program, that is, the program to deal with the order of execution and the execution of the sequence so that the conditions, the directed line segments on the way to indicate the control flow from a processing to the next processing.

System structure diagram of the program: the reaction is the call relationship and hierarchical relationship of the modules in the system, who calls who has a sequential relationship. The directed line segments on the way indicate that the program control from the calling module to the called module, and implicitly when the end of the call control will be handed back to the calling module.