The first 8 variables are from the BGI
functions. GraphDriver and GraphMode are codes for the highest resolution screen available
on the machine. MaxX and MaxY is the
number of pixels in the x and y axes. MaxColors
is the maximum number of colors in the
display. Most of this information is available in the structures
maintained by the BGI and the autodetection functions. The
structure viewinfo contains most
of this information after a call to the BGI function
detect. The structure lineinfo contains a
discription of the line types and thicknesses. Consult the
Borland library reference manuals about these variables.
Two vectors hrefs and vrefs contain the locations of horizontal and vertical
reference lines. The user can specify at most 20 horizontal and
20 vertical reference lines. The members are stored in a
circular fashion: the 21'st reference line overwrites the 1'st
reference line. The variables nvrefs and nhrefs
count how many reference lines
have been declared. The number of horizontal lines that will be displayed
will be 20 if nhrefs is 20 or more. Only the 20 most
recently declared lines will be displayed.
The next two functions control the output. Pause()
allows the graph to be displayed until a
key is pressed. It will also terminate the program if you press
the ESC key. gprintf() is
similar to printf() in C. The first two arguments are the
locations of output relative to the current viewport. The
variable argument list contains a format string for output, and a list
of variables. This function calls sprintf() to create the string
in 140 character buffer. This is dangerous if you put
more than 140 characters for output since you will overwrite
memory in ths sprintf() call.
The data is stored in the virtual matrix grf
. The data matrix has 4 columns. The first is
the graph number, the second is the symbol to be used for
displaying the graph, the third is the data for the x axis, and
the fourth is the data for the y-axis. You can have as many
graphs stored in grf as you want. The number of graphs is stored
in the variable grfnum. You add
them by concatenating the graphs vertically. There is a public
member function for this. The data for the graph is supplied in
a kx2 matrix where the first column is the x data and the second
is the y data. The symbols and graph counts are maintaned
automatically.
The last function plotpoint()
puts a symbol at point (ix,iy) relative to the current viewport.