o
o
o
o
o
o
o
o
o
.....
-
Print
head
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•
•
• •
•••••
• •
• •
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• ••••
•
••••
•
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•
Figure
2-2.
The
print
head
has
nine
pins
When
the
MPS
1200 receives a signal
from
the computer, the
electronics inside the
printer
cause certain pins
in
the print head to
strike the ribbon, creating a vertical pattern
of
dots
on
the paper.
The
print
head then shifts slightly, prints
another
column
of
dots,
shifts again, and so on, until the letter
is
formed. As the
print
head
moves across the page, a line
of
characters is printed.
Then
it
reverses direction
and
prints
another
line
of
characters
as
it returns.
This process
is
called bidirectional printing.
The
correct sequence
of
strikes and
movement
of
the
print
head for
each character
is
stored in the printer's
memory.
The
printer selects
the character pattern
you
want
based
on
a numerical code it receives
from
your
computer.
These
codes are
part
of
a set that
is
used
throughout
the
computer
industry. It
is
known
as
the American
Standard
Code
Jor
Information
Interchange,
or
ASCII (pronounced
as
ask-key).
ASCII
CODES
Most
of
the time
you
don't
need to be concerned about ASCII
codes. When
you
type a letter A
on
your
keyboard, the
computer
knows
which
ASCII code to send to the printer.
But
if
you
want
to
send a
nonprinting
code
to
your
printer, to change to italics
or
compressed
print
for example,
you
need to
know
the ASCII code
and
how
to get
your
computer
to send it.
2-2
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