Required Terminal Capabilities

Any terminal which is to be used with qed must support the following capabilities:

• Direct Cursor Addressing
• Screen Clearing
• Zero width escape sequences

The last point requires further explanation. On some terminals, an escape sequence to turn on inverse video takes up a character position on the line. As a result your standard 80 column line will be reduced to 78 columns (one character to turn on, and one character to turn off) The qed editor does not work properly on this type of terminal. Escape sequences must not take any physical room on the screen.

Although not required, the following capabilities are recommended

• Clear to end of line.
• Insert and delete line.
• Inverse video (and to a lesser extent underline).
• Up, down, left and right cursor keys.

The first two will speed up display updates while the third is necessary for displaying tagged blocks of text. If your terminal supports Highlighting or underline, but not inverse video, then qed will attempt to display tagged areas of text using these capabilities. Without cursor keys, the editor may be painful to use.