Structure Charts
According to the text a structure chart is a hierarchical diagram that shows how an information system is organized. In other words a structure chart is something that shows how an information system is organized. In the early days of computers (the 1940's and 1950's) computer programs had to be small because of the restrictions of the computers they were written for. Later the computers grew bigger and had more power, so the programs could become bigger and more complex. Even more important: the users of the systems came up with more requirements. The result of this was a need for tools for analyzing and implementing systems that were better entailed for complex systems. In the early 1970's, Larry L. Constantine, together with Edward Yourdon, came up with the concept of structured analysis and structured design. In fact, structured design continues giving guidelines, where structured programming stops. Not only Constantine and Yourdon, but also Stevens and Myers added new ideas to the principle of structured programming. One of the main tools that are used in structured design is the structure chart, developed by Constantine. The structure chart is a variant of the HIPO-technique designed by IBM
is normally more closely related to other functions in the modules rather than closely related to each other. DFD's are often used at a high level of modeling, for example information flows between departments but are a data oriented where structure charts are process oriented. The processes of a DFD can be worked out in a structure chart with two techniques known as transaction analysis and transformation analysis. Transaction analysis indicates the transaction types of the system and the usage of those as design parts. Transformation analysis is the strategy of deducting a structure chart from every design part, isolated by transaction analysis. Temporal cohesion is the opposite of procedural cohesion in that the modules are related, but sequence and specific order do not matter in any way. In logical cohesion the information is hardly related at all. In a logically cohesive module the information is executed from outside the module. The worst and final method of cohesion is coincidental cohesion. This type of cohesion is the worst type of cohesion of them all because the instructions do not have any relationship together at all. These are the seven types of cohesion that are used in structure charts and that help to execute the instructions in the system. According to the textbook, a module is a self- contained component of a system, defined by function. For large systems, several levels of STC (structure charts) will be needed to reflect the number and complexity of the modules in the system, regardless of whether multiprocessing or multitasking is in use. Furthermore, the advent of packages in languages such as Ada also creates the need for more than one level of STC, where the higher-levels show the interactions between the package specifications (to use the Ada terminology) and lower-levels of STC are used to define the package bodies. To avoid intersection calls, and for large systems, STC's contain named on-page connectors and off-page connectors. These objects allow calls between modules on the same or separate STC's to be shown as a pair of calls, one to the on-page or off-page connector, and the other from another on-page or off-page connector with the same nam
Some common words found in the essay are:
Cohesion Cohesion, Typically STC, IPO's HIPO's, Modules According, Stevens Myers, Background According, Generator CGEN, Edward Yourdon, structure charts, Structure Diagrams, structure chart, Related Techniques, type cohesion, on-page off-page, cohesion sequential cohesion, seven types, off-page connector, cohesion sequential, structured design, off-page connectors, transaction analysis, seven types cohesion, on-page off-page connector, input process output, cohesion type cohesion,
Approximate Word count = 1489
Approximate Pages = 6 (250 words per page double spaced)
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