d/lloodd11_75

ommand level) prompt will be either @' or $' depending on
certain options, which will be discussed later. For now we will assume the
prompt is @. This is the place where commands given are executed immediately.
Certain characters are also available for use here (and other places) which
make life on a TOPS-20 easier. Here is a list of those characters:

1) DC: This gets the system's attention. It will break out of most programs and
processes. It may be necessary to type 2 for it to work, though.
3) DO: Halts terminal output without interrupting the program. A second DO
restarts output to terminal. Note: under this condition output is still being
sent by the computer, it is just not printed on the terminal, as opposed to
an actual ceasing of output by DS.
4) DS: Temporarily pauses current output.
5) DQ: Resumes output currently suspended by DS.
6) DR: Retypes current line discarding old line.
7) DT: Prints information including what the program in use is doing, CPU
information, and loa