Flow chart introduction

Rules of block diagram representation

The flow chart is a means to visually present the flow of data through an information processing systems, the operations performed within the system and the sequence in which they are performed. In this lesson, we shall concern ourselves with the program flow chart, which describes what operations (and in what sequence) are required to solve a given problem. The program flow chart can be likened to the blueprint of a building. As we know a designer draws a blueprint before starting construction on a building. Similarly, a programmer prefers to draw a flow chart prior to writing a computer program. As in the case of the drawing of a blueprint, the flow chart is drawn according to defined rules and using standard flowchart symbols prescribed by the American National Standard Institute, Inc.

A Flow Chart is a diagrammatic representation that illustrates the sequence of operations to be performed to gain the solution of a problem. Flow charts are generally drawn in the early stages of formulating computer solutions. Flowcharts facilitate communication between programmers and business people. These flowcharts play a vital role in the programming of a problem and are quite helpful in understanding the logic of complicated and lengthy problems. Once the flowchart is drawn, it becomes easy to write the program in any high level language. Often we see how flowcharts are helpful in explaining the program to others. Hence, it is correct to say that a flowchart is a must for the better documentation of a complex program.

A simple flow chart example

It is not strictly necessary to use boxes, circles, diamonds or other such symbols to construct a flow chart, but these do help to describe the types of events in the chart more clearly. Described below are a set of standard symbols which are applicable to most situations without being overly complex.

Rounded box - use it to represent an event which occurs automatically. Such an event will trigger a subsequent action, for example 'receive telephone call', or describe a new state of affairs.

Rectangle or box - use it to represent an event which is controlled within the process. Typically this will be a step or action which is taken. In most flowcharts this will be the most frequently used symbol.

Diamond - use it to represent a decision point in the process. Typically, the statement in the symbol will require a 'yes' or 'no' response and branch to different parts of the flowchart accordingly.

Circle - use it to represent a point at which the flowchart connects with another process. The name or reference for the other process should appear within the symbol.

The following are some guidelines in flow charting:

In drawing a proper flow chart, all necessary requirements should be listed out in logical order.

The flowchart should be clear, neat and easy to follow. There should not be any room for ambiguity in understanding the flow chart.

The usual direction of the flow of a procedure or system is from left to right or top to bottom.

Only one flow line should come out from a process symbol.

Only one flow line should enter a decision symbol, but two or three flow lines, one for each possible answer, should leave the decision symbol.

Only one flow line is used in conjunction with terminal symbol.

Write within standard flow chart symbols briefly. As necessary, you can use the annotation symbol to describe data or computational steps more clearly.

If the flowchart becomes complex, it is better to use connector symbols to reduce the number of flow lines. Avoid the intersection of flow lines if you want to make it more effective and better way of communication.

Ensure that the flowchart has a logical start and finish.

It is useful to test the validity of the flowchart by passing through it with a simple test data.

Дата добавления: 2017-01-14