Silicon Graphics IRIS Series Terminal Manual page 75

Appendix F
1 2
\0 \0 \0
\0 \0 \0
\0 \0 \0
\0 \0 020
end
(in the file io.c) calls
ginit()
then makes a call to
which calls
xginit()
line 6 bits at a time, preceded by the graphics escape character which is ASCII
^P = DLE = 16 (decimal) = 020 (octal). Each six-bit pattern has 040 (octal)
added to it so that it is in the range of printable characters.
In the example above, the nulls are represented by \0, the DLEs by 020, and
every other character by itself. The blanks in the table are ASCII spaces (040
octal). The string "end" marks the end of the table. In the case above it is
obviously necessary, since the final character sent is a space. Future examples
will omit the first three lines of nulls, since
so every example will begin with 2 nulls. Finally, note that there are exactly 16
entries in each line - this is important if the lines happen to end with spaces.
In this example only we shall explain one command in some detail; almost all
of the others can be worked out in the same way from the files lib.c and io.c.
Consider the command
equivalent to the call
this:
color(arg1)
short arg1;
{
}
sends a DLE (= 020), followed by 34 (= 100010 binary) sent in two six -
gcmd()
bit chunks. First the low-order 6 bits are sent after adding on 100000 (binary)
giving 1000010 (binary) = 0102 (octal) = ASCII 'B'. The six high-order bits are
all zero, so adding 100000 (binary) to it gives an ASCII' '(space).
sends DLE, then 'B', then a space.
sends a 1 as 2 six-bit chunks followed bv a two-bit chunk (low-order
sends()
bits first). The chunks are treated exactly the same way as the
and the net result is a '!' followed by two spaces.
sends nothing—it just causes any host-buffered characters to be
gexit()
flushed.
Version 1.3
3 4 5 6
\0 \0 \0 \0
\0 \0 \0 \0
\0 \0 \0 \0
020
netinit()
setslowcom()
.
gcmd(83) gcmd()
color(RED)
. In
color(1)
gcmd(34);
sends(arg1);
7 8 9 10
\0 \0 \0
\0 \0 \0
\0 \0 \0
3 ! 020 B
which first sends out 50 nulls, and
. calls
setslowcom()
puts a 12 bit number out on the serial
ginit()
. RED is the constant 1, so this is
, the color routine looks something like
lib.c
IRIS TERMINAL GUIDE
11 12 13 14
\0 \0 \0 \0
\0 \0 \0 \0
\0 \0 \0 \0
!
. Then
gcmd(0)
will always be called first,
71
15 16
\0 \0
\0 \0
\0 \0
020 8
calls
ginit()
thus
gcmd()
does,
gcmd()