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a she-philospher.com Library publication |
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Library Catalog No. DC1980 |
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| Information packet on D-Charts, with articles from the late-1970s (Item 1 of 4) | ||||
| by Kim Harris, et al. | ||||
| e-Copyright © 2004–2016 < http://she-philosopher.com/library.html > see also Part 1: Editor’s Introduction for Library Cat. No. DC1980 |
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D-CHARTS
(Anonymous; 26 March 1980)
Using This Document
We are explaining D-Charts in four parts:
1. What is a D-Chart?
2. How to D-Chart
3. D-Chart Symbols and General Structures
4. Overall Example of a D-Chart
What is a D-Chart?
A D-Chart is a new and easier kind of flow chart. Basically, a D-Chart is a network of downward-flowing lines, with a few symbols, that graphically represents your program. We are grateful to Kim Harris for our knowledge of this superior method.
The D-Chart is a design tool, rather like a schematic. You work from your D-Chart; it is not a nasty bit of documentation to be provided after the program exists. Using a D-Chart makes coding easy; most of the work is already done. And, a D-Chart makes it possible for you to write structured definitions that will be “legal” in the language.
D-Charts are a better way of “flow charting” than the traditional ANSII Standard. They can be used effectively with either structured or non-structured programming. D-Charts are better because they are easier to write, and easier to read. As they are more compact, less space is used; this adds to their readability. None of the awkward boxes of ANSII flow charting is used.
How to D-Chart
There’s not much to it! The main line of the program flow is on the left (see Overall Example of a D-Chart). All constructs branch off to the right from it. Symbols for the beginning and ending of loops or constructs are numbered; this is especially helpful with nested constructs. Error symbols are also numbered; these numbers reference your error table.
These guidelines will help:
- A D-Chart of the overall program is written as a design tool AS THE PROGRAM IS BEING THOUGHT OUT.
- D-Charts of the specific program modules and submodules are written as these program portions are designed. New D-Charts are written as changes to existing code are designed.
- D-Charts are written BEFORE CODING.
- TOP DOWN DESIGN — BOTTOM UP CODING AND TESTING!!
There are few rules in D-Charting, but they are important. Basically, they are:
- One way in; one way out.
- ALL structures must be closed. ONLY exception: a fatal program error that will stop the sequential program flow. (See “Error” symbol.)
- In a conditional phase, the “true” portion of the phrase is on the right.
- The “entry” (definition) name, at the top of the D-Chart, is underlined.
D-Chart Symbols
Terminate construct; return to sequential program flow.
All words along the way will be executed.
Pre-Test
Body of loop may or may not be executed.
Post-Test
Body of loop executes at least once.
Words along only one of the several paths will be executed; which path depends on the value of the top stack element. (This example shows four possible paths.)
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» Item 3 of 4 (D-Charts, by Kim Harris, September 1976)
» Item 4 of 4 (5 sample D-charts)
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