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Here is what you will get. The top line is printed bi-directional-
ly, and the bottom is printed uni-directionally. You will have to
look hard because there isn’t much difference.
Let’s analyze the program. Line 20 sets the line spacing to
7/72 of an inch so that the characters that we print will touch top
to bottom. Lines 30 - 50 print 10 vertical line characters. Then
line 70 sets one-direction printing and the vertical lines are
printed again. Finally line 110 sends a form feed to advance the
paper to the top of a new page, and then uses the master reset to
restore the printer to the power on condition.
You can also set the printer to print in one direction for one
line only by using the (ESC) “(” command. This command im-
mediately moves the printhead to the left margin and then
prints the remainder of the line from left to right.
W The seven bit dilemma
Certain computers (but not the IBM-PC fortunately!) don’t
have the capability to send eight bits on their parallel interface.
They can only send seven bits. This would make it impossible
for these computers to use this printer’s block graphics
characters and special symbols if our engineers hadn’t thought
of a solution. (All of these characters have ASCII codes greater
than 127 which means that the eighth bit must be on to use
them.) The solution lies in the three control codes given in the
following table: