Graphics Display Program for Zenith 2-19 Video Terminal Greg A. Gerhardt
University of Kansas, Lawrence, KS 66045 We have developed a FORTRAN graphics package for the Zenith Z-19 video terminal that uses the graphics character set of the Z-19 and generates a 72-line X 80 character display from a normal 24-line X 80-character screen. This note describes the software and its capabilities. The program GRAPHICS is designed to read and display previously stored X-Ydata arrays. It can also he incorporated into instructional or experimental programs that manipulated data in an X - Y format. The software is capable of handling u n t o 144 data ooints. but can he easilv altered to handle lareer sets. Data sets of greater than 72 points are automatically disolaved . " in two segments. The uroeram . - -generates and draws the axes, lahels and titles the graph, creates the data display, and automatically expands the X-Ydata to fill the screen. The increased line resolution is achieved by software selection of three graphics characters that differ only in their position on a line of the CRT. Careful selection of the characters allows for la cement of a data ooint a t the tov, middle, or bottom of a line. This effectively crkates a 72-line field from a 24-line terminal. The software is interactive and easy to use. There are only three commands: 1) "carriage return" to read another data file and display it; 2) " Q to quit the graphics program; and 3) "S" to segment the currently viewed data file and display an expanded portion of that file. This fast, simple, and versatile graphics package is suitable for displaying titration curves, spectra, calibration curves, and a variety of other X-Ydata; however, the video terminal is not a high resolution display, and the present software does not draw lines between the data points. We currently use this graphics package to display in viuo and in uitro electrochemistry data (concentration versus time). Examules of data disnlavs are seen in Fieures 8 and 9. range of the databoints. Figure 9 is an expanded segment of Figure 8 showing the software capability for viewing small portions of data sets and greatly enhancing the resolution of the data display. Program GRAPHICS-Microsoft FORTRAN-80 ver 3.13 has 357 statements and 110 comments. Program runs on a Cromemco 2-2 microcomputer with 56K of RAM, Zenith Z-19 video terminal, dual 8-inch f l o ~ p vdisks and CP/M o ~ e r a t i n p
Figure 8. In v i m electrochemistry data dlsplayed on a Zenith 2-19 video terminal.
568
Journal of Chemical Education
Figure 9. Expanded portion of the display shown in Figure 8
of ~ h e m i s t r y , ~ ~ n i v e r sofi t ~y a n s l sLawrence, , ~~'66045.
An Axes-Drawing Program for the Hewlett Packard Digital Plotters T. D. L. Pearson and J. N. Demas,
University of Virginia, Charlottesville. VA 22901 Properly drawn and labled axes on plots are essential for the proper visualization and comprehension of plotted results. On many computer-plotter systems, provisions for generating and laheline axes are minimal or nonexistent. For examole. our Hewlet;-~ackard 9825A computer-9872A digital plotter has svstem software for drawing axes with tics and numbering. Further, there are no provisions for automatically inserting centered lahels on each axis. Finallv, s ~ e c i a lsymbols frequently used in our work such as 6 ,h, ";and 6 could not be included in the lahels but had to be hand drafted later. T o alleviate these problems, we have developed a program AXES that has the ca~abilitvof drawing labeled axes with properly oriented numeration on the abscissa; it also has provisions for including special characters in the lahels. AXES was written in Hewlett Packard's BASIC-like HPL to run on a Hewlett Packard 9825A calculator controller with a large format (11 in. X 17 in.) Hewlett Packard 9872A digital plotter. Because many of the plotting complexities are handled by the intelligent plotter, little difficulty would he experienced adapting the program to high level languages on any other computer connected to the plotter. The smaller (8% in. x 11 in.), less expensive, Hewlett-Packard 7225A and 7470A digital plotters are software interchangeable with the 9872A plotter and produce equally acceptable plots. Figure 10 is a sample plot. The Greek symbols are nonstandard characters; other characters could easily be added as needed. Final plots are thesis (31) and journal (32) quality. The plotter pens are disposable and come in a variety of colors and widths for added versatility and include acetate marking pens for making transparencies. If default values are not to be used, the operator initializes the plot parameters before drawing any axes. Variables are the plotting speed, the tic length, the pen color, the coordinates of the corners, as well as the slant, height, and height/ width ratio of the characters. These parameters are maintained throughout the rest of the plot. Infunnation Ear each of the axes is then entered. This includes whether or not to draw the axis, where to place the tics on the axis, and where, ~~~
