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CHAPTER 8
SPECIAL FEATURES
OF THE SD-lo/l5
In the previous chapters we have learned about several groups
of control codes. In this chapter we will look at more control
codes. These codes don’t fit neatly into any of the groupings that
we have studied, but they add a lot of capability to SD-lOjl5.
So here goes.
Commands covered in this chapter include:
l Bell
l Master reset
l Unidirectional printing
l Eighth bit control
l Block graphics
l International character sets
l Macro instruction
n Now hear this
You may have heard SD- 10/l 5’s bell if you have ever run out
of paper. And you may have wondered why it’s called a bell
when it beeps instead of ringing! It’s a long story that goes back
to the early days of computers, when teletype machines were used
for computer terminals. These mechanical marvels had a bell in
them that could be heard for blocks. This bell was used to signal
the operator that something needed attention. The code that the
computer sent to the teletype machine to ring the bell was, rea-
sonably enough, called a bell code. Well the name bell code is
still with us, even if the bell has changed to a beeper, and a lot
of people still call the beeper a bell, even if it doesn’t sound like
one. So with our trivia lesson out of the way, let’s see how we
can “ring the bell.”
The code to sound SD- 10/l 5’s “bell” is CHR$(7), which is
ASCII code 7 or < BEL > . Any time SD- 10/l 5 receives this code
it will sound the bell for a quarter of a second. This can be used