The character-based version of the runtime emulates graphical windows and controls by displaying characters with particular attributes that approximate the look and feel of a graphical system.
The following standard characters are used by default to represent various graphical components:
"-", "|", "+", "=", "*", ".", "^", "v", "<", ">", " ", "#"
Terminals that support a line drawing set or a special extended character set, or both, can be configured to use these special characters. The configuration method is similar to the one used for line drawing. To support the substitution of line drawing characters and extended characters, there are two terminal database functions: GO-GUI-MAP and GF-GUI-MAP.
The GO-GUI-MAP function uses a list of standard characters that correspond to line segments and other special characters when displayed in the terminal's graphics mode. The GF-GUI-MAP function provides a method for specifying substitute standard characters for some or all of the graphical components.
The Terminal Manager turns the terminal's graphics mode on by sending the GO code. The GO code is followed by normal characters that are interpreted by the terminal into their corresponding special characters. When all the special character elements have been displayed, the terminal is set back to normal mode with GF.