Graphics Commands on the IBM Personal Computer

Abstract

It will be assumed throughout the course of this book that the reader is reasonably familiar with the BASICA interpreter on the IBM Personal Computer (or IBM PC as it will be referred to). This understood, the best first approach to graphics on this or any new machine is to write small programs in order to get used to the graphical capabilities and any limitations of that machine. This first chapter, therefore, will look at some of the BASIC commands on the IBM PC that are concerned wholly or partly with graphics. The graphics statements will not be described in detail, you can get that information from the manual, but particularly useful applications of certain statements will be expanded upon. The display potential of the IBM PC is explored with a series of example programs and simple exercises. In the following chapters this knowledge will be used to develop a sound understanding, both practical and mathematical, of computer graphics in general. This book will concentrate on graphics and so not too much effort is spent in making the programs ‘idiot proof’ (or more politely ‘robust’). The code necessary to prevent nonsensical input from killing programs would confuse the underlying graphics theory: and anyway it is assumed that all readers of this book are very sensible people! It is a good exercise, however, to take the programs from the book and add the required robust code. Furthermore, machine code and assembler programs have been deliberately ignored, in the belief that the IBM PC user will program mostly in BASIC.