As the story unfolds we watch the progress of the idea as it responds and adapts to changing circumstances, slowly growing in complexity. This kind of story begins with the initial appearance of a young, simple idea. So this is not the only way the story could be told; it is simply the story as I am able to tell it. A professor of computer science – or someone who worked on IBM's CICS transaction processing monitor, or on the Mesa programming environment, or on the Andrew windowing system – would undoubtedly tell a different story, or at least tell it differently. The human father of the structured methods was Larry L. Their corporate father was IBM's Systems Research Institute. This mental model underlay the "structured" systems development methods in the 1970's. Raw materials come in one door; they are processed, processed, processed; and at the end of the processing, a finished product is pushed out another door.
The code examples are mostly in pseudo-code and Python, with the occasional bit of Java.
A transaction center of a system must be able to · get (obtain and respond to) transactions in a raw form · analyze each transaction to determine its type · dispatch on type of transaction · complete the processing of each transaction A dataflow diagram shows the logical functions that a system must perform, but it doesn't say anything about the design of the program that will perform those functions.
In structured analysis and design, a different diagram called a was used to show program design.
De Marco actually spent very little time discussing transaction analysis.
But the topic received more attention in Ed Yourdon and Larry Constantine's book .