Epson LX-80, Руководство по эксплуатации

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In thi s p ro gram we used the number 128 in the DATA statement s to
s ignal th e end of a print line . This is the reason for the IF-T HEN
st a tem e nt in line 610 that skips to line 650 and causes a line f eed.
Th e o th er s pecial technique used in this program is found in lines
620 a n d 630. Since some of the data numbers are repeat ed many
ti m es, negat ive DATA numbers have been used for repetiti o n s, in
order to save t y ping . Line 620 tests for a negative number a n d, if it
fi nd s one, re ads the next two numbers and prints their pin p a t terns
t h e n um ber o f times indicated by the negative number.
For example, when the minus 6 in line 800 is read, the prog ra m then
reads the nex t two numbers (8 and 0) and sends them to th e p rinter
six t imes. T his feature is not a necessary part of the program , but it
does a l low yo u to type fewer data number s.
Ot h erwise, t h e program is a straightforward graphics prog ram that
uses 7 - dot li n e spacing and reads numbers from DATA st a t ements
a n d sends t h e m to the printer . If you want to see the figur e in other
de n s it ies, cha nge the
" yO '
in line 600 to " L" or " Z ".
Graphics Programming Tips
N ow t hat we' ve shown you how to design your own graph ics, we'll
review and e mphasize a few elements of graphics programmi ng. As
usual, Micro soft BASIC ha s been used in the example s, bu t the
pri n ciples a pply to any programming language although th e r e may
be o t her way s than using a semi-colon to prevent carriag e returns
a n d line feed s being added at the end of a statement .
S emic o lon s and command placement
Af t er t h e gra phics command is issued, every number sen t t o the
LX - 80 is in t e rpreted as a pin pattern and printed on pap er . There-
fore, yo u m u s t be careful how you write graphics command s i n your
program.
F or exam pl e, suppose you want a 50-column graphics lin e with a
7- do t lin e s p a cing . You might enter the following program :
2 0 L PRINT CHR$(27) "K"CHR$(50)CHR$(0 )
3 0 LPRINT CHR$(27)"1 "
40 F O R G=l TO 50: LPRINT CHR$(74): NEXT G