Program notes software topics

While most programmers tend to think about the structure of a piece of software in terms of control flow — that is, which instruction is to be executed next and which routines call what other routines — software can also be envisioned in terms of data flow: Which program modules produce information and which modules consume it? For example, a data-entry module produces information for the rest of a system to process, while an output module consumes information sent to it from the rest of the system.