Flow Charting and Block Diagramming Techniques - All about the ...

Figure 16. Operational Flow Chart (Informal), IBM 650 Proceduresactually being done than a flow chart of a punchedcard procedure, because each step is considerably moreinvolved. For this reason, complete documentationof the application must include block diagrams ofeach processing step. The manner in which these areconstructed will be described in the next section.The labeling of an operational flow chart for adata processing system application is important whenit is to serve as a guide to programming and operating.It is at this point that tape and program identificationmust be introduced. Schemes have been developedwhich lead to great efficiency in systems planning andoperating, particularly with regard to:I. programming job assignments2. tape labeling and library maintenance3. job scheduling.A brief description of the highly efficient systemused at one installation can be found in the IBMGeneral Information Manual, "The IBM 705 Systemof Accounting at Southern Railway" (Form E20-6025) .Block DiagrammingA block diagram has been defined as a graphic representationof the procedure by which data is processed.Hence, one could assume that block diagrams wouldbe used to illustrate clerical, punched card machineand data processing system operations. While it istheoretically true that clerical and punched cardmachine functions can be block-diagrammed, thispractice is not followed since many of the steps areassumed to be understood by the clerk or machineoperator. Furthermore, in the case of machine operations,control panel wiring diagrams and planningcharts are more descriptive of the functions than ablock diagram would be.This discussion, then, will be concerned only withblock diagramming data processing systems functions.It might be argued that the coding sheet (or programmingform) is to the data processing systemsoperation what the wiring diagram and planningchart are to the punched card procedure. This is truein only a limited sense because the coding sheet lacksthe graphic qualities that the others have.One of the most important uses of the block diagramis to provide the programmer with a means ofvisualizing, during the developmental stages of programming,the sequence in which logical and arithmeticoperations should occur, and the relationship ofone portion of a program to another. The codingsheet does not offer this advantage.The amount of detail included in a block diagramwill vary according to the purpose it is to serve. In theearly stages of program development the primarypurpose of the diagram is to experiment with andverify the accuracy of different approaches to codingthe application. In this instance large segments ofthe program are represented by a single symbol.Once an approach has been established, a block diagramis prepared to serve as a basis for coding. At this18