Program Planning (Preparation of a Flow Chart)
A flow chart is a graphic method for indicating a proposed or actual solution to the problem. A flow chart shows the steps a computer performs to solve a problem. A programer usually develops a program flow chart before coding. A flow chart uses special symbols for representing various operations.
Creating flow charts is an art, not a science. It is not a cut and dried process with firm rules. Rather it offers the analyst and the programer an opportunity to give expression to their creative urges and to apply their creative powers to problem solving.
There is no unique ‘Correct’ flow chart for solving a given problem. Each programer can come up with his own flow chart provided some formal rules for drawing flow charts are observed. A set of commonly used flow chart symbols are given below.
Adhering to the following rules is considered to be a good flow charting technique.
- The direction of flow should usually be from the top to the bottom of the page and from the left to the right.
- Lines should never cross. Crossing lines can always be avoided by the use of a pair of connector symbols.
- Arrow-heads should be used to show the direction of the flow, especially, if it is other than top to bottom or left to right.
- The symbols may be of any size, only the shape is standard.
- Every flow chart should begin with a ‘Start’ symbol and end with a ‘Stop’ symbol. The start and stop will appear only once in each flow chart.
- These merely indicate the physical starting and ending points of the flow chart.
- The I/O symbol can appear at any point at which data is to be entered in the computer or any point at which data is being output from the computer.
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8. The next step in completing the flow chart is to mentally analyze the problem in order to obtain a logical sequence of processes. The process symbol is used to indicate the steps involved in manipulating the data into the desired result.
9. The basic contributor to flow charting complexity is the fact that questions must be answered during the processing, that is decisions must be made. In many instances, the computer must choose between two logical paths. Therefore, the program must reduce the required decision to a comparison of two values. The decision box must have at least two paths leading from it. Each path is labelled to indicate the condition which will cause the flow to follow a particular path.
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In certain circumstances, a programer may find it difficult to avoid crossing a line or to prevent drawing a long or jagged line between symbols. The connector symbol indicates a transfer of flow and thus, always must appear in pairs. An arrow-head leading into a connector indicates that control is to be transferred to the point at which that connector's counterpart appears. An arrow-head leading from a connector indicates the point at which control is to re-enter the flow chart.
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The printer output symbol indicates that the results are to be output at the printer.
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Program comment or annotation - a comment or a description inside the box can be used to clarify some point of the flow chart.
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Off-page connector indicates reference to another point on a different page.
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Magnetic-tape indicates that input/output is from magnetic tape.
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Magnetic-disk indicates that input/output is from magnetic disk.
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Magnetic-drum indicates the use of magnetic drum for input/output.