Data Diagrams

Abstract

The use of computer-generated diagrams to represent massive amounts of information in a simple, easy to understand pictorial form is probably the most widely used application of microcomputer graphics. Data collection of every kind has exploded with the advent of low-cost personal computers. Even the smallest companies now rely on computers like the IBM PC to keep records, to send bills and, just as important, to keep statistics on the state of the business. Reams of tabular numerical output are certainly not suitable for interpreting such masses of information. Data diagrams are the answer. Scientists have always used such pictures, but businessmen have considered them to be of secondary importance, mainly because of the time and expense needed for their construction. Computer graphics has ended all that. Now it is relatively straightforward to use microcomputers to construct instantaneously bar-charts, histograms, pie-charts, continuous and discrete graphs, as well as many other types of figure. This chapter will describe some techniques needed to produce an interactive programming package that will draw the above-mentioned diagrams. It is hoped that the reader will take the package and extend it, and then use the ideas presented here to create a program that will draw other types of diagram. Before running any of the programs given below, in fact before entering the BASICA interpreter, the user should type GRAPHICS so that the Print Screen key can dump out any diagram on the printer, and GRAFTABL so that space in the memory for a character set is organised and the pointers to this set are initialised.