Page:A contribution to computer typesetting techniques - tables of coordinates for Hershey's repertory of occidental type fonts and graphic symbols (IA contributiontoco424wolc).pdf/11

 4.1 The Table of Character Digitizations. In the Hershey system. characters are drawn by connecting lines between successive (x,y) coordinate pairs. The coordinates of each character are given in ‘raster coordinates’, which are integers ranging from 49 to —49. The (x,y) coordinates for each character in the occidental repertory are given in Appendix A. A useful quantity is the printer’s em, or the distance between the bottoms of two successive lines of close packed text. The em is 32 raster units for characters in the principal size, and 21 raster units for the indexical size.

The table in Appendix A is organized in the following way: The first column is the character number, the first pair of numbers separated by colons are the left and right boundaries of the character in raster coordinates, and succeeding pairs of numbers set off by colons denote the (x.y) set for that character. An (x,y) coordinate pair of (-64,0) indicates that the pen is lifted at that point in the character: a coordinate pair of (-64,-64) indicates that the end of the character has been reached.

An ASCll tape of the table in Appendix A is available for those desiring the digitizations in machine readable format. It can be obtained from the National Technical Information Service.

4.2 The Graphic Character Representations. Large scale drawings of the characters comprising the table in Appendix A are given in Appendix B. Coordinate pairs are denoted by small circles, and the left and right boundaries of each character (the character width) are denoted by short vertical lines. The character number is located in the upper left hand corner, and the origin of coordinates for each character is located at the center of each display. It should be noted that in the displays a right handed coordinate system is used in which the +x axis is toward the right and the +y axis is toward the bottom of the page. This is in accord with the normal printing convention in which distance down the page is considered positive.

4.3 Indices to Alphabets and Special Symbols. The names of the characters and symbols that can be generated from the tables in Appendix A are listed in Appendix C together with the numbers assigned to them in the Hershey system. It should be noted where alphabets are concerned, the table lists only the number for the first letter. Numbers for the rest of the alphabet follow in succession.

4.4 Applications. The original application of the digitizations was for use with the Hershey Typographic System. Figures 4 through 10 show some samples generated using the character set in conjunction with the Typographic System. Among these are examples from Dr. Hershey’s own mathematical publications (figure 4), a mathematical manuscript in German (figure 9), etc. Figure 11 shows some typical scientific text from a test run, made while interfacing the NBS typographic routines with the Hershey character set. Appendix C was also set with Hershey’s System.

The applications of the Hershey system discussed thus far were to publications requiring graphic-arts quality art work which must be produced on one of the more versatile COM devices or on a large flat-bed plotter. Certain of the character sets presented in this publication can be applied with profit by installations which have only a small drum plotter. While the characters generated on these ubiquitous devices suffer some deterioration, as can be seen from figures 12 et. seq., they never-the-less are an improvement over the lettering normally found on such devices. At NBS a subset of the occidental set has been converted into a FORTRAN subroutine which is used with a digital platter to provide graph titles of improved legibility {see figure 12). In another application, a sub-set of the occidental