Epson LX-80, Руководство по эксплуатации

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Thi s program has all the necessary elements. Line 20 has the co m-
mand for single-density graphics and specifies 50 columns. (Reme m -
ber that y ou must use two numbers to reserve columns even if you
o nl y need th e first one.) Line 30 has the correct command for the
lin e s p a cing , and line 40 calls for the printing of a pin pattern 50
t i m es. ( I f y ou wish, refer back to Figure 9-2 to see a represent a t ion
of the pin p at tern that 74 produces.)
Although thi s program has all the necessary elements , it will n ot
gi ve y o u the single pin pattern that you want, as you can see in t he
p art ial p r intout in Figure 9-6.
W h a t we nt wrong? To help you understand the graphics comm and
a nd av o i d so me of the more common errors made with it , le t us
e x a m i n e thi s program in detail .
F i rst l o ok a t line 20. <ESC> K calls for single-density graphic s, and
the t wo CHR$ numbers specify 50 columns of dots . Once that
c omm a nd i s given, the next 50 codes sent to the printer are int er-
p r e t e d as numbers corresponding to a pin pattern and printed on the
p a p e r . Sinc e there is no semi-colon at the end of the line, the nu m-
b er s 1 3 a nd l O-the codes for carriage return and line feed- are
se n t t o th e p r inter after CHR$(O). Because the graphics comm and
has b ee n i ss u e d, these codes are printed as pin patterns .
L in e 30 w ould normally be the command for 7-dot line spacing , but
s in ce th e gr a phics mode has been put into effect, the comman d is
i nt e rp rete d b y the printer as two pin patterns: 27 and 49 (the A SCII
co d es f o r <ESC> and 1). Since there is no semi-colon at the en d of
t hi s li ne, th e numbers 13 and 10 are sent again, and again the y are
p rint e d as pin patterns.
I n lin e 4 0 n o thing is sent to the printer until after the LPRINT . T hen
th e desired p i n pattern-74-is finally sent, but since no semic o l on
is af t er it, 1 3 a nd 10 are sent next each time the loop is execut ed.