The manual starts with several Chapters outlining the facilities available. It is hoped that these Chapters will act as a primer for the system. A more rigorous definition of the package and the SC 4020 is given in Chapters 8 and 9. The user is well-advised to read the description of the SC 4020 in Chapter 9 at least once as it will help to put the system in perspective. However, at this stage, we need only concern ourselves with the basic operations of the plotter and a brief description will suffice.
The SC 4020 can produce graphical output on a continuous roll of plain paper (not graph paper). The plotting area is divided up into pages (or frames) which are 7.5in square and it is possible to advance the paper automatically by an SC 4020 order, ADVANCE FILM. As the name of this operation implies, it is also possible to produce the output on microfilm but more of this later. The possible plotting positions on the page are not continuous. The square page is divided up into a 1024 x 1024 raster and all plotting positions must be approximated to by the nearest raster position. As these positions are about 0.007in apart, this should not cause any problems. It is also possible to plot one of the 64 hardware characters at any co-ordinate of the raster. In addition, straight lines can be drawn between any two raster positions.
From these simple operations, it is possible to produce a set of procedures for curve drawing, generating software characters from short vectors, producing a graticule and so on. It is important to remember that so far only the simplest form of operation of the SC 4020 has been described. It is not until Chapter 5 that we need to concern ourselves with the more sophisticated use of the SC 4020. Until then we shall assume that the user is producing graphical output on continuous paper. However, as stated earlier, it is possible to produce output on 35mm or 16mm microfilm. This means that it is possible to produce cine films on the SC 4020. The GROATS system has, therefore, been designed to aid the user in film-making as well as the more conventional graphical output.
