FUTURE
F'R~NT
NOTE:
In the
program
above, line 30 backspaces 12 times. Line 40 then
changes
to
italics
and
prints the
words
"FUTURE
PRINT"
again, directly
on
top
of
the first printing.
UNIDIRECTIONAL
PRINT
The
MPS
1200
normally
prints
one
line left to
right
and then prints
the
next
line
right
to left.
This
is called
bidirectional
printing. It
is
the
fastest
way
to
print
and
it
is
one
of
the reasons the
MPS
1200 can
print
at
120 characters
per
second.
With
bidirectional print,
however,
the vertical alignment
of
charac-
ters
from
one
line to the
next
is
not
always exact.
The
misalign-
ment
is
very
small
and
not
noticeable
in
most
applications.
But
occasionally, particularly
when
using block and line graphics, it
becomes
more
obvious.
For
applications
where
vertical
alignment
is
more
critical
than
speed,
printing
in
only
one
direction-unidirectional
print-is
the
answer.
Continuous
Unidirectional
Print
Format
BASIC
Hex
ON
chr$(27)
"U1"
1 B
D5
31
OFF
chr$(27)
"UO"
1 B
05
30
The
command
ESC
U controls
continuous
unidirectional print.
With
unidirectional print, the
print
head prints all lines
from
left-
to-right.
The
command
uses 1
and
0
as
its
on
and
off
switches. Sending the
printer
ESC
"Ul"
turns unidirectional
print
on;
ESC
"UO"
turns
unidirectional
print
off. Since the 1 and the 0
work
as
on
and
off
switches rather than actual characters,
you
can substitute
chr$(l)
and chr$(O) for their actual ASCII codes,
if
you
like.
9-6
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