Sharp PC-1500 - Page 86

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10 PAUSE "SPE CIFY TAX TAB LE TO USE:"
20 PAUSE "( 11 SINGLE."
30 PAUSE "(21 MARR IEO,"
40 INPUT " {3) BUS INE SS ?"; TT
50 IF (TT< 1) OR (T T> 3 ) THE N 10
60 REM USE APPR OPR IA TE TABLE
70 IF TT = 1 THE N 220
80 IF TT = 2 TH EN 300
90 IF TT = 3 THEN 450
(etc)
U si ng the ON s tatt ~ m e n t we can co ns oli date lines 70. 80 , and 90 into a single s tatemen t:
70 ON TT GOTO 220, 300, 450
ON ER ROR GOTO
Using anoth er · t' orm of c ontrolled transfer allO 'tv s a pr og ram to detect wh en an erro r occurs.
Aft er detectio1,, tl 'e program ma y exec ute stat em ents .. vhich at tempt to recover from the erro r.
S uc h stat em ent s may i nf orm and instruct the use r' , or they may save valuable data .
The ON ERROR GO TO statements in st r ucts SHARP who m to go up on dete ct ing the
occ urr ence of an c rror . The fo rm of th is statemen't is:
ON ERROR GOTO li ne.nu mb er
w he re li ne ·num be r is the number of a program l ime contai ni ng in structio ns to beo fo!!owed in the
event of an err or .
F. DISPLAY PROGRAMMING
The di sp lay wi nd oi.v incorpor ated into t he PC~1500 is a remarkably flexible ou tp ut devi ce . To
all o• _. , pro grammets to exp l oi t t he fu ll powe r of the display several new statemen ts have been
added to th e dialect of BA SIC u sed by the PC -1500. These extensions a re d e sc ribed in this
secti on .
The di spl ay itself ut ili zes l iqu id crystal tech no logy to display up to 26 characte rs at a ti me.
E ac h c ha ra ct er in the co1 n pute r 's charac te r set oc<:upies a 5 x 7 dot matrix. Ut ili zing the GPRINT
command, pro gr an i rners May devel op Md display t heir own characters.
For gr aph ic purposes , the e nt ire di SJ llay field may be uti li zed as a 7 x 156 dot m atr ix.
In dividual dots \Vith in a ny of 156 columns may lJe energized t,o create graphics, figures. or special
symbols.
The PO INT commar'd a lloi.·1s "s ens ing" of any co l umn to discover i.•1 hich d ots arc
curren tly energi led .
A s peaker and to ne ge ne rator ano .. v the programmer to add the dime nsion of sound to th e
man-ma ch ine in terac tion. T one s rnay be cre at ed . at any of 256 frequencies (ran ge 2301 ~ z to abo ut
7KHz). Autorn at ic repetition of a t one and control of th e duration of a tone ar e also po ssible
un der pro gram cont r ol .
F.1. BEEP
The BEEP st atement allows the programmer to cr eate tones for ga me playing , e rr or signalling,
and other interact iv e ap plic at ions. The format of the B EE P statement i.·1 hich create s so und i s:
~ expression 1 , exp ression 2 , expression 3
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