Sharp PC-1403 - Page 150

1 44
W hen th i s p r og ra m i s run it p r in ts th e wor d ' HELLO ' o ne
t i me .
10 GO SUB 100
2 0 END
100 PRINT " HELLO "
110 R ~ TURN
•¥f!,,1.u4
The group of st a t eme nt s i s i n c l u d ed in t h e p rog r a m a t s ome l oc at i o n w he re the y a r e not
reached in t he n orm a l s eq u en ce of exec ut ion . A freque nt l oca ti on i s after t he END
statement w hic h m arks th e end o f the m a i n prog r am . At t hose l oc ation s i n the main
body of the program-whe r e subro utin e s a r e t o be exec u ted -incl ude a GOSUB state-
ment with an exp r ess ion whi ch i n di c a t e s th e s t art i ng line numb e r o f the subroutine.
The last line of the sub ro ut i ne m u s t b e a RETURN . W hen GO S UB i s executed, the
COMPUTER tra n s f ers con t ro l t o the i nd i c at e d li ne nu mber and processes the state-
ments until a RETURN i s r eache d . C on t rol i s th e n t rans fe rred back to the statement
following the GOSUB.
A subroutine may i n cl ud e a GOSU B . Sub rou t i n e s may be " n es ted " i n this fa s hi o n up
to 10 levels d ee p .
The e xpre ss i on i n a G OS UB statem e nt m ay n o t in cl ude a c omm a, e .g ., 'A ( 1, 2)'
c anno t be used . S inc e the r e i s a n O N . . . GO SUB s t ru cture t or c ho os in g diff e rent
subrout i n es a t given l o c ati o ns i n th e pro g ra m, th e ex pr e s sio n u s u a ll y c onsis t s o f ju s t
th e de si r ed l in e nu mb e r . Whe n a nu m e ric e x pre ss i on i s u s ed , it mu s t e v a l uat e to a
valid l i ne nu m ber , i. e . , 1 to 652 79 , or a n ERR O R 4 w i ll occ ur .
••MW
Wh e n y ou w i s h to e xecut e the s ame g ro u p o f statem ents s eve ra l times i n the co ur se of
a pro gra m o r u se a p r ev i o usly w r i tt en set o f sta t e m en ts in s e ve r a l · pro g r ams , it is
con v enien t t o u s e the B AS I C capab i lit y f o r s ub ro utin es u s ing t he GOSUB and
R E TURN v er bs .
Th e GOSUB v erb is u sed t o exec ut e a B AS I C s u broutin e .
1 GOSUB e xp res sio n
Abbrevia ti on s: GO S ., GOS U.
See a lso: GOTO , O N .. G O S U B , ON .. . G OT O , RETURN
Verbs
GOSUB