Sharp PC-1500A Instruction Manual page 52

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Unfortunately, this program will just keep " • c hugging" along forever. (You may stop the
program by using the BR EAK key I. We should provide a way for such programs to end. We can
do this by using a "counter" along 'wVith an IF statement. A counter is a variable in which we
keep a record of how many times we
have
done
someth ing
(i.e. we count witlh it). With this
technique the IF statement will test whether we have performed our PRINT statements a predeter.
mined number of times. Of course, it is entirely UlP to us to determine the number of repetitions.
Let's pick 10 times for each PRINT statement (after 10 times I get bored).
Using our counter and IF statement we can write:
Program Listing:
10 WAIT 30
15
C =
1
20 PR
INT "CHUG CHUG CHUG CHUG"
30 PRINT " CHUG CHUG CHUG CHUG"
40 C = C+ 1
50 IF C< = 10 THEN 20
60
END
Keystrokes:
ITJ
m
00
rn
CD CD CD
(]J l•••••I
CD!IlO::JI = ICD I•••••!
rn mm
OlJ CD
ao
c:o
1SH"'1 c::i moo
OD
rn
1 •••c•1
mCBJODGDISP•c•I C£:J0DOD001•••c•I o;JCEJ
OD
[I) ls•OF•I
c:J
lE••E •I
m m mrn
CD
ao
[!]
fS><oFT I CJ ls .. cEI
lsP>CEI
l•••c•I
ISP•C•I
lS••CEI
m
OD
0:0
rn
lsPACEI
m
C[J
OD(][)
l•••c•J
moo m m
1 ...
cc1
mm on oo
1'""'1 C'.J
moo
mt =
1
m
rn rn
l•••••I
m oomm m1 ••"•1m1 = 1rornrn ao mao
m[101 ••r<•I
mrnmOTJrn1 ..... ,
Follow the operation of the counter as each lo op is executed . Notice that in line 15 we must
assign the counter an initial value. On line 40 we increment this value to reflect one more
execution of statements 20 and 30.
There are many other ways to use counters an.d loops within programs. Unfor·tunately, we do
not have the space to describe them here. We suggest that you pursue your education \.Vith one
of the books listed in Appendix F.
The GOTO instruction is a command as well as a statement. As a command its use is naturally
d ifferent from its use as a program statement. Issued as a command, in the RUN mode, GOTO
begins program execution in a manner similar to the RUN command. T he difference lies in certain
internal preparations w·hich are made before instructions of the program are performed. (For a
50
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