Sharp PC-1403

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6. U s e TRON and TROFF , ei t he r a s co mmands or d i r e ctl y w it hin t he progr a m to tr a ce
th e flow o f the pr ogram thr ough in divi dual l ine s . S t op t o e xamine the c onten ts of
crit i cal vari ables a t cr u c i al po i nt s . Thi s i s a v e ry s l ow way t o find a pro b l em , but
so m et ime s it is al so the o nly w a y .
When ente r ing a ne w BA S I C prog r am, it i s u s u al fo r i t no t to wo r k t h e fir st ti me . Even if
you are s impl y key i ng i n a progra m t hat y ou kn ow i s co rrect , s u c h a s t hos e provided in
this manual , it is usua l t o m ak e at l eas t o ne t yp i ng er r o r . I f i t i s a ne w progr a m of a ny
l e ngth , it will pro ba b ly cont a i n a t l e as t on e logi c e rro r as w e l l. F oll ow i ng are so me
general h i nts on how to find and c o rr ec t yo ur e r ro r s .
Y o u r un yo ur p r o gr am and ge t a n e r ror m e ss a ge :
1 . G o b ack t o t he PRO gram mo de a nd use t h e [D o r the [D k e y to r eca ll the lin e
wi th t he e rro r. T h e cu r sor will b e po s itio n ed at t he place in t he l ine whe r e the
COMPUTER got co n f u sed .
2 . If you can ' t f ind an ob vio u s e rror in th e w a y i n wh i c h t he line i s w r i tt e n , the probl e m
may lie wi t h t he v a lu e s wh i ch are be i n g u s ed . F o r example, C HR$ ( A ) will produce
a spa c e if A h as a va l ue o f 1 . C h eck t he v a l u e o f e ach v aria ble in eit her the RUN o r
the PROgram m ode b y ty p ing i n t h e n am e of th e vari able followe d by I ENTER I .
You RUN the pr og ram a n d don ' t ge t a n error mes s a ge, b ut it do e sn't do wha t you
expect.
3. Check through the p ro g r a m line by li ne us i n g LI ST a nd th e [ 1 ] and [I] keys to
see if you have entered th e prog r am c or r e ctly . i t i s sur p r is ing how many errors can
be fixed by just taking ano t he r l ook a t t he p ro gr am .
4. Think about each l ine as y o u go th rou gh t he p r og r am as if y o u were the computer.
Take sample va l ues and t ry to ap ply the o p er a t i o n i n each line to see if you get the
resu l t that you expected .
5 . Insert one or more e x tra PRINT state m e nts in y o u r p ro gram to di s play key values
and key location s. Use thes e t o i so lat e t he p a rts of the program tha t are working
correctly and th e loc at ion of the e rr or . Th is app ro a ch is also use f u l for determining
which parts of a p rogr a m h ave b een e xe c ute d. Yo u can al s o u s e STOP to
temp o rarily h alt e xe c ut ion a t cr i t i c al poi nt s so that se v era l va r ia bles c an be
examined .
BASIC De.b o gging '
Troubleshooting